INDIAN NATIONAL SCIENCE ACADEMY

INDIAN NATIONALREPORT FORIUGG 2003

TWENTY THIRD GENERAL ASSEMBLYINTERNATIONAL UNION OF GEODESYAND GEOPHYSICS, SAPPORO, JAPAN(June 30 – July 11, 2003)

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NATIONAL COMMITTEE FOR INTERNATIONAL UNION OF GEODESY& GEOPHYSICS (IUGG) 2000-2003

Dr. H.K. Gupta, FNA, Department of Ocean Development, New Delhi - ChairmanProf. Sri Niwas, FNA, IIT, Roorkee - MemberDr. A. Bhattacharya, FNA, IIT, Kharagpur - MemberDr. S.W.A. Naqvi, FNA, NIO, Goa - MemberProf. B.N. Goswami, FNA, IISc, Bangalore - Member

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CONTENTS

1. Preface

Harsh Gupta

2. Geodesy and Gravimetry

Prithvish Nag and B. Nagarajan 5

3. Geomagnetism and Aeronomy

G. S. Lakhina 18

4. Hydrological Sciences

S.N. Rai 59

5. Meteorological and Atmospheric Physics

V. Thapliyal 80

6. Physics and Chemistry of the Oceans

E.Desa 115

7. Seismology and Physics of the Earth’s Interior

R.K.Chadha and D.Srinagesh 143

8. Volcanology and the Earth’s Interior

Abhijit Bhattacharya 159

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PREFACE

On behalf of the IUGG National Committee of the Indian National Science Academy, it is a great pleasure forme to present the Indian National Report for the period January 1999 through December 2002, to the 23rd

General Assembly of IUGG, at Sapporo, Japan.

This has been a very fascinating period for Geodesy and Geophysics in our country. While the Survey of Indiacelebrated 200 years of their establishment, highlighted the great trigonometric survey done some 200 years agobetween Cape Camorin and Banot in high Himalayas; Bhuj had the distinction of having the most damagingearthquake on 26th January 2001. This was the largest and deadliest earthquake in the subcontinent since the15th August 1950 Assam earthquake.

Prithvish Nag and B. Nagarajan have compiled a report on Geodesy and Gravimetry involving the work done byseveral major organizations in the country. They have underlined the transition from GTS to GPS. Lakhina hasreported on Geomagnetism and Aeronomy. He points out that India offers a unique geophysical location forinvestigating complex processes related to the earth’s interior as well as electro-dynamical processes occurringin the ionosphere and the magnetosphere. He underlines that very useful work has been done by Indianscientists in investigating problems related to dynamics of earth’s interior, solar-terrestrial relationships andspace weather using experimental, analytical, and modeling techniques. S N Rai reports on HydrologicalSciences and draws attention to the increase in demand of water supply with the passage of time. India has 1/6th

of world’s population with only 4% of world’s water supply. His compilation provides in brief the work done inhydrology, including ground water assessment and development, water quality, ground water recharge, rain fall-runoff, flood, sedimentation and glacier’s hydrology. Thapliyal reports on Meteorology and AtmosphericSciences. He mentions that more than 30 organizations, including universities and institutes, carry out workrelated to monsoons, atmospheric modeling and dynamics, climate studies, air-sea interaction, atmosphericboundary layer, satellite meteorology, atmospheric physics and related experimental studies. Results ofimportant programmes like INDOEX (Indian Ocean Experiment), BOBMEX (Bay of Bengal MonsoonExperiment) and ARMEX (Arabian Sea Monsoon Experiment) are reported. Chadha and Srinagesh haveprepared the section on Seismology and Physics of Earth’s Interior. The report period saw a major overhaulingand addition of new broadband digital data acquisition capabilities in the country and new trends in research.Bhuj earthquake drew the attention of all scientists in the country. Abhijit Bhattacharya reports on Volcanologyand Earth’s Interior, and highlights important findings in the Himalayan region, Deccan Province, Central India,and other important geological units of the country.

In a nutshell, it may be said that the period of 1999 through 2002 witnessed a very active research phase inIUGG-related work in India.

I am thankful to all the contributors of the articles in the Report, to R.K. Chadha and D. Srinagesh in helping mein compiling this Report, Mrs. Prerna Singh and P. Radhakrishnan for secretarial assistance. I would also like tothank the IUGG National Committee members and officers of the Indian National Science Academy, especiallyDr. A.K. Moitra, for their help in bringing out this Report.

Harsh Gupta, FNAChairman, National Committee for IUGG,Indian National Science Academy, New Delhi;Department of Ocean Development,Government of India,New Delhi 110 003, India.dodsec@dod.delhi.nic.in91(11)24360874 (Tel); 24362644 (Fax)

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GEODESY AND GRAVIMETRY

Prithvish Nag and B. NagarajanSurvey of India, Dehra Dun-248 001

Introduction:

Geodetic and gravity surveys providecritical inputs in understanding thegeodynamics of the earth system. Variousorganizations and institutions in India areinvolved in geodetic measurements ofcrustal deformation with which one cantest geophysical models to infer earth’sdynamics. In addition to thesemeasurements, more recently GlobalPositioning System (GPS) techniques arebeing used to study local and regionproblems of crustal deformation.Nonetheless, because of the time scalesinvolved, older geodetic data ( includingleveling, triangulation and repeatgravimetric) continue to be important formany geophysical studies. In thefollowing pages, a brief account of thework carried out in the field of geodesy(geodetic and geophysical) in the countryduring the period Jan 1999 to Dec. 2002 isgiven. The report deals with the workcarried out by:

ÿ Geodetic & Research Branch,Survey of India, Dehra Dun,Uttaranchal.

ÿ Indian School of Mines, Dhanbad,Jharkhand.

ÿ Space Applications Centre,Ahmedabad, Gujarat.

ÿ Indian Institute of Geomagnetism,Mumbai, Maharashtra.

ÿ Geological Survey of India,Kolkata, West Bengal.

ÿ Andhra University College ofScience & Technology,Visakhapatnam, Andhra Pradesh.

ÿ Center for Earth Science Studies,Thiruvananthapuram, Kerala.

ÿ National Geophysical ResearchInstitute, Hyderabad, AndhraPradesh.

ÿ Oil and Natural Gas CorporationLimited, Dehra Dun, Uttaranchal.

Geodetic & Research Branch is one of theoldest and a specialized directorate ofSurvey of India with the primaryresponsibility of providing precise firstorder horizontal and vertical control inIndia and its islands for topographicalmapping in the country, geodynamicstudies and Project surveys etc. Nationalgravity and geomagnetic coverage,monitoring and maintenance of tidalstations all along Indian coast (both onmainland and islands) etc., are also few ofthe additional responsibilities vested withthis directorate.

Over the years with the improvement oftechnology particularly after the dawn ofsatellite era, the requirement of speed andaccuracy has increased considerably. Tokeep itself at par with the rest of the world,of late this directorate has adopted moderntechnologies.

The specialized tasks being carried out bythe directorate during the period underreport are as enumerated below:1. Horizontal and Vertical Control

and GPS Surveys2. Gravimetric Control3. Geomagnetic Control4. Tidal observations5. Project SurveysHorizontal and Vertical Control andGPS Surveys

Horizontal Control

Horizontal control of the first order isprovided primarily as the framework forthe topographical mapping. Thisinformation is also being used for otherproject surveys, geodynamic and damdeformation studies and checking of theverticality of archaeological structures.For densification of horizontal control andother studies which have been undertakenduring the period under report, GPSobservations at 462 stations, 470 line km.EDM traverse and 18.0 line km. Invar

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Base were observed in the various parts ofthe country.

A project to redefine the Indian GeodeticDatum in context to Deep Continentalstudies has been taken up with an aim to i)to adjust Indian Geodetic Network usingthe method of simultaneous least squareadjustment of linear equations byincluding all Laplace Azimuths (272) andBase lines (12) observed / measuredbefore and after 1880 adjustment, as wellas inclusion of all new and revisedGeodetic Series Observed after 1880adjustment, ii) to determine the seventransformation parameters between Worldgeodetic system 84 (WGS-84) and ourlocal geodetic system, so as to make useof all Doppler / GPS observationspresently available and to make availablein future and iii) to critically examine thesuitability of Everest Spheroid as our localreference datum.

The Indian Geodetic Datum adopted in1880 is the Everest Ellipsoid, which isbased upon the adjustment of availablegeodetic data and has been designed usingthe computational means, mathematicalmodels and adjustment techniquesavailable at that time. This datum is notsuitable for High-Precision Geodetic andallied activities of modern age as it wasdeveloped using inadequate volume ofdata, measurements of base lines in Indianfoothills gave distortions to the tune of 3ppm and other unavoidable factors whichexisted at that time. Thus the challengingtask for an integrated re-adjustment of allthe geodetic data available today andredefinition of the datum using suchadjustment has been undertaken.

Vertical Control

Densification of Vertical Control:

For densification of vertical control 580line km. High Precision Leveling in Foreand Back direction was carried out in thecountry during the period under report.Earlier, the First Level Net for Indiaincluded data collected from 1858 to 1909,was adjusted in 1909 thus establishing theFirst Vertical Datum for India. The

methodology and instruments used fordata acquisition during that period did notmeet the accuracy requirements laid downlater, in 1912, by the InternationalGeodetic Conference. But the quality ofdata improved later with the introductionof Invar Staves in 1929-30 and also withthe adoption of Vignal's formulae forleveling errors and tolerances as adoptedby IAG in 1948. The Adjustment of 1909also suffered from an arbitrary system ofweighting and was constrained to fit theLocal Mean Sea-Level values at 9 ports.

A large number of High PrecisionLeveling lines have been run in the last 6decades across the length and breadth ofthe country using the latest Instrumentsand Invar Staves. A need was thereforefelt to have a Second Adjustment of theIndia Level Net including all linescompleted till date.

The first Phase of Second Level NetAdjustment was done in 1983. It coversthe Peninsular Shield considered to begeologically stable. 50 Leveling lines wereincluded in 17 circuits for this adjustment.Local MSL of Bombay based on 38 yearsobservations with mean epoch 1955 wastaken as the datum instead of the mean of9 ports taken at the time of First Level NetAdjustment. Now it has been decided touse geo-potential number and computeHelmert Orthometric Heights at places forredefining the vertical datum for India.

GPS Surveys

Geodetic & Research Branch of theSurvey of India has been associated withcrustal movement studies using geodetictechniques in various regions of India.Studies to monitor seismotectonics ofcentral region of southern peninsularshield covering an area of around 500 x500 sq. km. which include prominentfeatures viz., Narmada-Son lineaments,Godavari & Kakenada-Midnapur faultzones was taken-up during the periodunder report.

ÿ Five permanent stations withinter-station spacing of 40-60 kmand GPS stations located across

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and along the fault zones at adistance of order 2-10 km, wereestablished.

ÿ GPS and High Precision LevelingSurvey were conducted during theperiod from 1999 to 2002 to detecthorizontal and vertical surfacedeformations if any, respectively.

ÿ G P S o b s e r v a t i o n s f o rdensification, geodynamic studieshave been carried out in theSouthern Peninsular Shield andthe various parts of the country.During the period under report,GPS observations were carried outat the 96 GPS stations. 27deformation pillars were alsoconstructed and observationsconducted on them for earthquakemonitoring.

ÿ A network of GPS stationsconsisting of quadrilaterals andtriangles has been established formoni tor ing se ismotectonicactivities.

ÿ GPS observations were alsocarried out on 11 stations toprovide control to variousgovernment agencies such asI n d i a n S p a c e R e s e a r c hOrganization, Defense ResearchDevelopment Organization andIndia Air Force.

GPS observations for GeodynamicStudies

To study the post earthquake geodynamicprocesses GPS observations were carriedout in the states of Gujarat andUttaranchal. Observations on 33 stationseach in Gujarat and Uttaranchal werecarried out during the period under report.

A three years project "GPS campaign formonitoring crustal movements in aroundPalghat Gap Region southern PeninsularIndia" sponsored by the Department ofScience and Technology, Government ofIndia has been taken up since 2001. Theproject is aimed to study the seismogenic

potential of Palghat gap, the majortopographic expression in the WesternGhat region in Kerala with Particularreference to the epicentre of 1994Vadakkancherry tremor. Three GPS semipermanent stations (less than 100 km)were established on the terraces of thePWD Rest Houses at Kodungalore(Trichur district) Tirur (Malappuramdistrict) and Shornur (Palghat district) inKerala. Monuments comprising of RCCpillars measuring 60 cm tall and 30 cm x30 cm square face were constructedhaving 15 cm. Stainless steel boltembedded within it to mount the GPSreceivers. The GPS data logging went onfor four days simultaneously at thesestations using Trimbble's 4000 SSi Dualfrequency - multichannel geodeticreceivers and choke-ring antenna.Subsequently during 2002, three moresemi-permanent (less than 100 km) werealso established on the basements rocks atAttappadi (Palghat district), Nelliampathy(Palghat district) and Peechi (Trichurdistrict). Besides four local stations (lessthan 20 km) near Shornur were alsoestablished on the basements rocks atKundanur, Vellur, Amaiyur andEzhimanged around the epicentral regionof the 1994 Wadakkancherry tremor.

GPS Observations to ComputeTransformation Parameters

The reference frame for the GPS is WorldGeodetic System – 1984 (WGS – 84).GPS measurements at terrestrial sites,therefore gives co-ordinates on WGS-84datum. This datum is different from theIndian Geodetic Datum i.e., EverestSpheroid. All Survey of Indiatopographical maps are based on thisdatum. In order to make optimum use ofGPS based co-ordinates system, it hasbecome very essential to determineTransformation Parameters for conversionof co-ordinates from WGS-84 Spheroid toEverest Spheroid and vise versa. Thisproject is at the final stage completion.Reconnaissance and observations on 248stations were carried out during thedifferent field seasons and the adjustmentof GPS observation network was done inthe Everest Spheroid.

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GPS Data Centre and Permanent GPSStations

National GPS Data Center has been set upin Survey of India for archival anddistribution of GPS data from severalpermanent s ta t ions se tup forseismotectonic studies in India under theaegis of the Department of Science &Technology, Government of India. Thedata archived at National GPS Data Centerwill be distributed to various sisterscientific organizations on demand basisfor seismotectonic studies in India.Survey of India has the responsibilities of5 permanent stations. Data from 8Permanent stations has been received atthe Data Center so far, for archival,analysis and distribution.

Gravimetric Control

The gravimetric work carried out bySurvey of India include, execution of aprogram of 15 km gravity mesh,observations along selected profiles andleveling lines, computation and study ofvarious gravity anomalies, repeat gravityobservations in earthquake prone areas etc.At present, there are 56 standard gravitystations in the country, which are beingused for densification work. The 15 km.gravity mesh coverage of the entirecountry is being carried out which will besubsequently used for preparation ofGravity Anomaly Maps (Free air,Bouguer & Isostatic) at various scales bothin analogue and digital form fordistribution to geoscientists on demand. Incontinuation of gravity studies beingcarried out in the country under NationalGravity Program, Survey of India hasestablished 1013 Gravimetric Stationsduring 1999-2002 which brings the totalnumber of stations observed so far toabout 13713 stations which coversapproximately 59% area of the country.Efforts to develop high-resolution geoidcombining EGM96 global geopotentialmodel and terrestrial gravity anomalies forIndia are under progress.

Gravity Observations on Bench-Marksalong H.P. Leveling Lines

Gravity observations are integral part formeasurements of height above verticaldatum (i.e. geo-potential number). Thegravity observations on 555 bench-marksalong various H.P. Levelling lines above20° Latitude in India have been carried outduring the period under report and 2393bench-marks were connected by gravityobservations in connection withadjustment of Level Net in India. Thus, thenumber of stations observed so far alongselected profiles and for other controlprovided at an interval of 1 to 8 km.including the number of benchmarks isabout 14,843. The total number of stationsat which gravity values have beenobserved up to December 2002 has goneup to 34,691. This includes 56 standardgravity stations and 8807 benchmarkstations.

Gravity Observations for GeodynamicStudies

Several gravity measurements have beendone to study geodynamics of local andregional scale in certain earthquake proneareas of the country. For example,

ÿ Repeat gravimetric observationson 245 gravity stations during1999-2000 and 213 gravitystations during 2000 and 555stations were carried out in 2001-2002 in and around earthquakeaffected area of Gujarat,Rajasthan, Uttaranchal, H.P. andHaryana.

ÿ Repeat gravimetric observationson 129 gravity stations during1999-2000, were carried out inKangra-Dharamshala area ofHimachal Pradesh.

ÿ Repeat gravimetric observationshave also been carried out on 200gravity stations during 2000-2001in Gujarat and Rajasthan.

ÿ Repeat gravimetric observationson 220 gravi ty s tat ionssimultaneously with H.P.Levelling on bench-mark stations

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have been carried out during2001-2002 along the existing H.P.Levelling lines in Gujarat andRajasthan.

Geomagnetic Control

Geomagnetic observations all over thecountry are necessary for development ofGeomagnetic Modelling of Earth and forpreparation of Geomagnetic AnomalyMaps. Observations of Declination,Horizontal Force and Vertical Force at 138repeat stations, 104 Profile stations and 15field stations were carried out in variousparts of the country for preparation ofIsomagnetic charts for Declination,Horizontal Force and Vertical Force forepoch 2000.0.

Tidal Observations

The responsibility of carrying outsystematic tidal observations andmonitoring of tidal stations were entrustedto Survey of India in 1877 and since thendata collection work is continued at anetwork of tidal observatories locatedalong East and West Coasts and alsoAndaman & Nicobar and LakshadweepIslands. Sea-Level data from about 24Tidal observatories, collected during thelast 10 decades, is utilized mainly todetermine Mean Sea-Level to serve as theVertical Control Datum for heights for thecountry and for tidal predictions fornavigational purposes. Tide tables areprinted a year in advance and madeavailable to National/ International usersto facilitate their navigational activities.Monthly/ Annual Mean Sea-Level of thefunctional ports are also sent to PermanentService of Mean Sea-Level (PSMSL) UKas an International commitment.

Continuous and updated actual tidal datareceived from various observations alongIndian coast have been used:

ÿ to determine Mean Sea-Level andMean Tide-Level.

ÿ to compare with prediction todetermine percentage accuracy.

ÿ for Analysis and Investigation toimprove tidal predictions.

ÿ to study Sea-Level variation andother Scientific Investigations.

National Tidal Data Centre

A National Tidal Data Centre wasestablished under the project NationalOcean Information System (NOIS) andSea Level Monitoring and ModellingProject (SELMAM) which were funded bythe Department of Ocean Development,Government of India. Indian Tide Tablescomprising of tidal predictions of 76 ports(44 standard ports between Suez andSingapore and 32 received from foreigncoasts viz. European, African, Chinese,Japanese and South East Asia Coasts) arepublished annually. Hugli River TideTables comprising of tidal predictions of 6Hugli River ports viz., Mayapore, Gangra,Haldia, Sagar, Garden Reach andDiamond Harbour are also publishedannually.

Precision Leveling Surveys for someselect dam sites

In order to provide accurate planimetricand height control in connection withinvestigation and planning for variousirrigation and Hydro-Electric Projects invarious parts of the country the precisetraverse and base measurements and HighPrecision / Precision Leveling were carriedout during the period under report. Someof these projects are, Tala Hydro ElectricProject, Tehri Hydro DevelopmentCorporation, Koteshwar Dam Project,Bhakra Dam Project, Ban Sagar FeederCanal Project, National Atlas andThematic Mapping Organization(NATMO) Kolkata, Purlia PumpedStorage Project, Jhuj Canal Project(GERI) and Rihand Dam Project.

Geodetic Leveling for EarthquakeStudies

(i) 214 line km. of Precision Levelingwas carried out in both directionson line Parli to Latur in the stateof Maharashtra for EarthquakeMovement Studies, during season1999-2000.

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(ii) 138 line km. of Precision Levelingwas carried out in both directionson line Tuljapur to Borgaonbuzurgin the state of Maharashtra forEarthquake Movement Studies,during season 1999-2000.

(iii) 212 line. km. of PrecisionLeveling was carried out in bothdirections on line Latur to Matalain the states of Maharashtra andKarnataka for EarthquakeMovement, during season 1999.

(iv) 586 line km. of H.P. Leveling wascarried out on line Jabalpur toBilaspur and Maharajpur to Sagarfor Peninsular Shield &Earthquake Studies, during season1999.

(v) 488 line km. of H.P. Leveling wascarried out in both directions online Devaprayag to Badrinath inthe state of Uttaranchal forEarthquake Movement Studies,during season 1999-2000.

(vi) 250 line km. of H.P. Leveling wascarried out on line Gendawad toGangotri portion Gendawad toDunda in the state of UttarPradesh and Uttaranchal forEarthquake Movement Studies,during season 1999-2000.

(vii) 544 line km. of H.P. Leveling wascarried out on line Saharanpur toGangotri in U.P. and Uttaranchalfor Earthquake Studies, duringseason 1999-2000.

(viii) 338 line km. of H.P. Leveling wascarried out on line Jabalpur toBilaspur in Madhya Pradesh forEarthquake Studies, duringseasons 1999-2000.

(ix) 252 line km. of Precision Levelingwas carried out on line Latur toBorgaon buzurg in both directionsin Maharashtra for EarthquakeMovement Studies, during season2000-2001.

(x) 296 line km. of H.P. Leveling wascarried out on line Santalpur toBhuj in Gujarat for EarthquakeStudies, during season 2000-2001.

(xi) 140 line km. of H.P. Leveling wascarried out on line Dhulia toBijapur in Maharashtra forEarthquake Studies, during season2000-2001.

(xii) 184 line km. of Precision Levelingwas carried out in both directionon line Parli to Parli inMaharashtra for EarthquakeMovement Studies, season 2000-2001.

(xiii) 85 line km. of H.P. Leveling wascarried out on line Saharanpur toGangotri portion Bhaironghati toGangotri in Uttaranchal forEarthquake Studies, during season2001-2002.

(xiv) 1175 line km. of H.P. Levelingwas carried out on line Santalpurto Lakhpat via Bhuj, Bhachau forEarthquake Studies in Gujarat,during season 2001-2002.

Specific Research Programs

Exploration for Oil

Advent of satellite altimetry has been aboon for oil exploration. The underlyingconcept of the technique, 'Satellite GravityMethod', is that the sea surface height,measured by satellite altimeter, whencorrected for dynamic variability e.g.tides, waves, eddies etc. corresponds tomass distribution of the underlying earth.Satellite Gravity Method is highly cost-effective requiring limited ship-bornesurveys. SAC (ISRO) and KDMIPE(ONGC) have jointly developed themethodology / related software forgenerating offshore geoid and gravitymaps and an Atlas of the satellite-derivedgeoid/ gravity maps over the surroundingIndian offshore in 1:7 million, 1:3.5million and 1:2 million scales has beengenerated. Gravity anomaly mapsgenerated are useful to ONGC particularly

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beyond 200 m. isobath. Few potential sitesidentified are west of Bombay High, Northof Laccadive ridge (Arabian Sea) andPalar basin, and part of Bengal Fan Delta(Bay of Bengal). The gravity maps havebeen used by the Directorate General ofHydrocarbons for giving Tenders tooutside agencies. Efforts are on to obtaincopyright for the technique "SatelliteGravi ty Method for OffshoreExploration".

Coal

The gravity surveys in Nuagaon-Teleshiblock of Talchir Gondwana basin, Anguldistrict Orissa indicated a high Bougueranomaly of the order of 40 mgal having acorroborative magnetic anomaly of theorder of 400 nT. This anomaly has beeninterpreted to be due to the presence ofhigh-density rock within the basement aswell as due to basement uplift. Thesurveys have established the presence ofCoal bearing Barakar formation at shallowlevel in the uplifted block.

Diamond

Gravity magnetic surveys carried outaround Mundapalli and Telepukapanivillages, Bargarh district, Orissa forkimberlite/ lamporite brought out a highgravity anomaly zone of the order of 0.6mgal over a strike length of 1.8 km inMundapalli area. This amomaly zone isassociated with high amplitude magneticanomalies and low resistivity values.Gravity surveys for exploration ofkimberlite/ lamporite pipe rocks inAnantapur and Mahboobnagar district,Andhra Pradesh, indicated a gravity highin SE part of the area. In the Tokepal area,Chattisgarh, the gravity surveys indicateda bull's eye anomaly that is encouragingand is being examined further for diamondprospect.

Gold

Gravity surveys in Dona, East block ofJonnagiri schist belt, Kurnool district,Andhra Pradesh indicated two majorfaults. One of these indicated a possiblezone for gold mineralization. Gravity

surveys carried out in Tsundupalle schistbelt, southern extension of veligallu schistbelt, Andhra Pradesh, have brought out thedisposition of Tsundupalle schist belt asgravity high and high nosings. Thegeologically mapped two linear bands inthe northern part of the schist belt appearsas a single band in the gravity map withwidth varying from 2 to 3 km and depthabout 2.5 to 3 km. Three E-W gravitytrends showing higher gradients areindicative of prominent crustal breaks. Theintersection of these linears/ trends withthe N-S trending schist belts areconsidered favourable zones for gold andbasemetal mineralisation and emplacementof kimberlite pipes.

Chromite

Gravity-magnetic surveys in Cuander-Bhushal area, Dhenkenal district, Orissa,indicated a number of magnetic anomalies.Two of these anomalies are associatedwith gravity high of the order of 0.5 to 0.6mgal, but are of limited strike length.

Groundwater

Gravity surveys in Sivaganga district,Tamil Nadu have brought out a column ofthick sediments that may have a bearing ingroundwater exploration.

Tectonic Studies

Bouguer gravity values along a sectionTanakpur-Pithoragarh-Tawaghat roadUttaranchal, show decreasing trendtowards northeast. A broad gravity high ofabout 40 mgals has been obtained aroundPithoragarh and a sharp gravity gradient isrecorded between Dharchula andTawaghat indicating probable thinning ofcrust around Pithoragarh.

Repeat Micro gravity surveys during thelast two years along Siliguri-Gangtoktransect revealed a change in gravityvalues with a maximum variation of theorder of 96 microgal. Repeatmeasurements will be continued for atleast five years.

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Gravity-magnetic surveys of semi-regionalnature along Mairang-Shillong andBarapani-Nongpoh have revealed majorstructural elements falling in and aroundTyrsad-Barapani shear zone.

A gravity magnetic profile along Bhuj-Nakhania-Sumarasar, Gujarat, over alength of 24 km from south to north, hasindicated a variation in gravity valuesfrom - 5 mgal in south to + 5 mgal in thenorth. A disturbed zone has been indicatedabout 12 km north of Bhuj with highgravity and magnetic values indicatingprobable uplift of high density and highsusceptibility material.

Geophysical Mapping

A total of about 1500 (1999-2000) and 800(2001-2002) stations at an interval varyingfrom 500 m to 1 km were occupied bygravity measurements in logisticallydifferent terrains of upper Assam andArunachal Pradesh for identification(delineation) of basement structures.Another 6000 stations were occupied bygravity measurements at a station intervalof 2 km in the area adjoining Narmada-Tapti rivers to delineate the Mesozoicsediments beneath the Deccan trap cover.The Bouguer gravity anomaly maps haveindicated deepening of granitic basementstowards north of Lucknow - Kanpur area.A major lineament trending NE - SW hasbeen delineated by gravity magneticsurveys.

Gravity and magnetic surveys in the eastof Kolar schist belt, Karnataka havebrought out a linear contact zone betweengranitoid gniess and charnockitic group ofrocks with a high gradient from Tirupathurto Ambur. Bouguer gravity contour mapin the northern part of Chitradurga schistbelt, Karnataka has shown a trend in theNW-SE direction and is influenced by twoE-W structural features, one betweenPondarahalli and Nandipura and the otherbetween C.K. Halli and C.R. Halli.Gravity anomalies of Manganese depositsof Vizianagaram districts, Andhra Pradeshwere interpreted by modelling. The locatesof supergene enrichment were identified

and the structures of Manganese horizonsdelineated. The exercise of modelling ledto the Geological setting compatible withgeological processes.

Gravity surveys are being carried outimparts of Eastern Ghat region covered by17º 30’ N to 18º 45’N and 82º, 30’ E to84º 15’ E with the objective of identifyingfaults and correlating the frequent earthquake occurrences in the region with thesefaults. Some space and frequency domainmethods of interpreting Gravity anomaliesof sedimentary basin, when the density ofthe constituent sediments increases withdepth, were developed. These methodswere applied to interpret gravity anomaliesof Pranhita-Godavari valley.

The Bouguer gravity profile along Kotban-Hodal-Palwal-Ballabhgarh-Badarpurtraverse in Haryana has indicated a gravitylow between Bamnikhera and Palwal,which is flanked by two highs on eitherside. Presence of horst and graben typestructures are inferred. Bouguer gravitycontour map in Haryana indicated nosingtowards southwest, between Pakasma andSamchana, and nearly a parallel trendbetween Kultana and Matan wherecontours are bulging towards northeast.This indicates a subsurface displacementof blocks.

The Ghaziabad–Hapur- Garhmuketeshwargravity-magnetic profile in U.P., shows aflat trend from Ghaziabad to east of Hapurbefore Koli river indicating a variation ofBouguer gravity value from -55 to -58mgal. After crossing the Koli river, thegravity values have shown an abruptchange of -20 mgal in a stretch of 35 km.The sudden fall in gravity values may beinterpreted as a fault/ downwarp inbasement. Regional gravity-magneticsurveys between Kanpur to Sheopura andPilwa to Ras, Ajmer, Pali and Naguardistricts, Rajasthan have delineated agravity high zone trending NE-SW over alength of 38 km indicating the extension ofAravalli range under soil cover. A faultzone running parallel to the gravity highzone has also been inferred in the westernpart of the area.

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Gravity magnetic surveys in Dauki-Amlarem-Muktapur area in Meghalayarevea led s ign i f i can t s t ruc tura lelements/fault in the area. A gravity highc losure a round Shi l long c i tycorresponding to a magnetic bipolaramomaly to the west of Shillong was alsoobserved.

Gravity surveys in the area betweenSursura and Beawar, Ajmer districtRajasthan, recorded higher gravitygradient zone in the west and gentler in theeast indicating asymmetrical structure ofthe basement configuration.

Bouguer gravity contour map in southPurulia/ Tamar-Porapahar rift zone inPurulia district, West Bengal, indicated asignificant feature along E-W directionthat could be correlated to TamarPorapahar south purulia shear zone. Thegravity contour map in Purulia clearlydepicts a shear zone striking E-W. Thegravity values vary from -14 mgal fromnorth to +4 mgal towards the south of thearea.

Gravity surveys in Kerala were done todelineate deep continental structures andassociated tectonics in and around Palghatgap region bounded by 10-12 N and 75.7 -78 E, During the first phase of the work(1983 to 1984), 41 auxiliary gravity baseshave been established with respect toCoimbatore Airport gravity base station.Subsequently, 128 auxiliary gravity baseshave also been established in similarmanner. In addition, direct air ties havebeen made with the help of daily domesticflights in 1987 to update observed gravityvalues at Coimbatore and Trivandrumairport gravity bases with respect to theIGSN-71 gravity base at Bangaloreairport. Datum corrections for Coimbatoreand Trivandrum airport gravity bases havebeen estimated to be -16.83 mGals and -16.60 mGals respectively. These baseshave been used to occupy intermediatestations at closely spaced interval fordetailed studies. At present, there are 172gravity base stations including two IGSN-71 gravity bases at Trivandrum andCoimbatore Airport, and 3200 detailed

gravity observations mostly concentratedin and around Palghat gap region. All theusual gravity corrections have beenapplied to the observed gravity data,except tidal and terrain corrections, andanomalies have been estimated. Thecontour maps of elevation, Free air,Bouguer and crustal thickness have beenprepared. The anomalies are beinginterpreted to understand deep continentalstructure and associated tectonics.

An Absolute Gravimeter was procured andinstalled at NGRI. First absolute gravitymeasurements to accuracy of microgalwere recorded at NGRI, Hyderabad. It isproposed to make absolute gravity basenetwork in India.

Mapping of Sea Bottom Topography

Geoid’s variation over the area of interesthas been used for prediction ofbathymetric anomaly along the satellitetracks using a model. ERS-1 35 daysrepeat cycle altimeter data were used toderive sea-bottom topography over a partof the western offshore (14-19º N, 67-72ºE.)

Joint Gravity Map

A joint Gravity map over the Indiansubcontinent using EGM96 (Earth GravityModel), NGRI gravity and ERS-1altimeter data has been generated over theIndian Peninsula and its surroundingoceans which is being further studied forregional tectonic patterns.Coastal Geomorphology

Mapping of coastal landforms andmonitoring shoreline changes along entireIndia coast in 1:250,000 and 1:50,000scales has been completed.

Geoid Modeling

Geoid investigations in India haveremained sketchy. The continental marginsof India continue to remain poorlyunderstood with regard to their structure,tectonics and evolution. In the absence ofwell - distributed seismic data, geoid datacan provide important insights in this

14

direction. Similarly, the obliquesubduction of the northeastern IndianOcean lithosphere at the Andaman islandarc trench system deserves specialattention. The oblique subduction isfurther rendered complex by the presenceof the Ninety East Ridge overriding thesubducted lithosphere. Geoidal surfaceover the eastern Indian offshore has beengenerated using ERS-1 altimeter data.Also, three- dimensional residual geoidvariation over the Andaman trench valleyhas been generated and the relatedsubsurface modeling studies have beeninitiated.

GPS studies to estimate strain field

Many GPS campaigns have beenundertaken in various earthquake pronezones of India viz. Western Maharashtra,Bhuj region of Gujarat, Chamoli region inUttaranchal, North Eastern Indian region.Some of the important results are:

ÿ Magnitude of the averagehorizontal velocity of Deccan trapregion in ITRF 96 is 51 mm/yr N47º E. The estimated dilatationalstrain is about 0.4 micro strain/yrin average.

ÿ An extensional strain regime isobserved along the west coasttranscending into a region ofcompressive strain towards theinterior of the shield area. Theextensional s train regimecoincides with the West CoastGeothermal Province.

ÿ The Murbad region in Thanedistrict of Maharashtra is under E-W compression and N-Sexpansion regime. Intra-platemovements are detected aroundAmberji.

ÿ The East, West, North, South andvertical components of thebaseline Lodai - Ratanpar (passingthrough the epicentral area) showno co-seismic displacementsassociated with 26th Jan., 2001Bhuj Earthquake.

ÿ N-S compressional strain of about0.1 micro strain/yr found inbetween Ratanpar andDhamdkapir.

Publications

Bijendra Singh and Guptasarma D.(1999).New method for fast computation ofgravity and magnetic anomalies due toarbitrary polyhedra, Geophysics, 66, 521-526.

Bijendra Singh, (2001). Simultaneouscomputation of gravity and magneticanomalies resulting from 2-D object,Geophysics on line, G7, 801-806.

Bijendra Singh and Guptasarma D. (2001).Joint modelling of gravity and magneticfields- A new computational approach,Current Science, 81, 1626-1628.

Chandrasekher D.V. and Misra D.C.(2002). Some geodynamic aspects of Kuchbasin and its seismicity: An insight fromgravity studies, Current Science, 83, 492-498.

Chandrasekher D.V., Mishra D.C.,Poornachander Rao G.V.S. andMallikharjuna Rao J.M. (2002). Gravityand Magnetic Signatures of VolcanicPlugs relate to Deccan Volcanism inSaurashtra India and their Physical andGeochemical properties, Earth andPlanetary Science Letters, 201, 277-292.

Grover, J.S, Srivastava, V.P and S.V.Singh (1999). Sea Level Rise AlongIndian Coast" XIX th INCA congress,GOA, Oct., 1999.

Gupta H.K., Harinarayana T., KousalyaM., Mishra D.C., Indra Mohan, Rao N.P.,Raju P.S., Rastogi B.K., Reddy P.R. andSarkar D. (2001). Bhuj earthquake ofJanuary 26, J. Geol. Soc. Ind., 57, 275-278.

Guptasarma D. and Bijendra Singh (1999).New scheme for computing the magneticfield due to a uniformly magnetizedarbitrary poly hedra, Geophysics, 64, 70-74.

15

Issar, D.P. (1999). Techniques of geodeticsurvey Network in Dams" and "Analysisand Interpretation of InstrumentationData, case studies of Geodetic Monitoringof Dams ( i ) Pong Dam (H.P.) (ii) RihandDam (U.P.)Workshop on Instrumentationin Dams, Inc lud ing , Se ismicInstrumentation, Nasik, Maharashtra, Feb.,1999.

Issar, D.P, and S.K. Singh. (1999).Geodetic Control Surveying andGeodynamic Studies in NE and NWRegions of Himalayas using GlobalPositioning System (GPS), Symposiumon " Snow, Ice and Glacier-A Himalayanperspective, GSI, Lucknow, March 1999.

Issar,D.P and H.B. Madhwal (1999).Mapping of Road and Linear Featuresthrough GPS, XIX th INCA congress,GOA, Oct., 1999.

Issar,D.P and H.B. Madhwal (1999). AnInsight into the transformation parametersWGS-84 vis-à-vis Everest System , XIX thINCA congress, GOA, Oct., 1999.

Issar, D.P and V.P.Srivastava (1999).Development of Tidal Measurements inIndia, XIX th INCA congress, GOA, Oct.,1999.

Issar. D.P. (2001). Need for RedefiningIndian Geodetic Datum, XX INCAcongress, Dehra Dun, Feb./ March 2001.

Issar,D.P and H.B.Madhwal (2001). FromGreat Trigonometrical Triangulation toGlobal Positioning System, XX INCAcongress, Dehra Dun, Feb./ March 2001.

Majumdar T.J., Mohanty K.K., MishraD.C. and Arora K, (2001). Gravity imagegeneration over the Indian subcontinentusing NGRI/ EGM96 and ERS-1 altimeterdata. Current Science, 80( 4), 542-554.

Majumdar T.J., Mohanty K.K., MishraD.C. and Arora K. (2001). Gravity imagegeneration over the Indian subcontinentusing NGRI/EGM96 and ERS-1 altimeterdata, Current Science, vol. 80 (4), 542-554.

Mishra D.C., Chandrasekher D.V.,Venkata Raju D. Ch. and Vijaya Kumar V.(1999). Analysis of gravity and magneticdata over Lambert Glacier, Antarctica andits relation with Gondwana rift valleys ofIndia, Earth and Planetary Sci. Letters,172, 287-300.

Mishra D.C. and ChandrasekherD.V.(2000). Proterozoic plate tectonics,Assoc. of Explo. Geophysics, 26, 22-25.

Mishra D.C., Singh, B., Tiwari V.M.,Gupta S.B., Rao, M.B.S.V. (2000). Twocases of continental collision in Indiaduring Proterozoic period-an insight fromgravity modelling constrained fromseismic and Magnetotelluric studies,Precambrian Research, 99, 149-169.

Mishra D.C., Singh B.B, Gupta S.B., RaoM.R.K.P., Singh A.P., ChandrasekherD.V., Hodlur G.K., Rao M.B.S.V., TiwariV.M., Laxman G., Raju D.Ch. V., VijayKumar V., Rajesh R.S. and Chetty T.R.K.(2001). Major lineaments and gravitymagnetic trends in Saurashstra, IndiaCurrent Science, 80, 1059-1066.

Mishra D.C. (2002). Crustal structureunder Indian Continent, Spl. Issue ofIndian Minerals, on occasion of 150 yearsof GSI.

Mishra D.C. Singh, B. and Gupta S.B.(2002). Gravity modelling across Satpuraand Godavari Proterozoic Belts:Geophysical Signatures of Proterozoiccollision zones, Current Science, 83, 1025-1031.

Mukhopadhyay M., (2000). Deep CrustalStructure of the West Bengal BasinDeduced from Gravity and DSS Data,Jour.Geol. Soc. India, 56, 351-364.

Nagarajan, B. (2001). Height accuracyachievable using GPS Measurement forSeismic Monitoring by Inter. Conf. onSeismic Hazard with particular referenceto Bhuj earthquake, January 26 Delhi Oct.,2001.

Nagarajan, B. (2001). Crustal Deformation

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Studies through GPS Measurements,Asian GPS Conf. on GPS and itsapplication, New Delhi, October, 2001.

Nagarajan, B. (2001). Need forIntroduction of a Regular Projection &Grid System for Cadastral Mapping, XXIINCA congress, Hyderabad, December'2001.

Nagarajan, B. (2002). Redefinition ofIndian Geodetic Datum", an Invited paperpresented by B. Nagarajan, InternationalSymposium- Weikko A HeiskanenSymposium on Geodesy at the OHIO StateUniversity, Columbus, OHIO, Oct 1-4,2002.

Rajesh S. Majumdar T.J., and Mitra D.S.,(2002). Geological structural patternidentification/ analysis in the eastern offshore, India, using satellite altimeter data.Geol. Surv. Spl. Pub. No. 74,231-240.

Rajesh S. and Majumdar T.J., (2002).Generation of 3-D geoidal surface of theBay of Bengal lithosphere and its tectonicapplications. (Accepted for publication inInternational J. of Remote Sensing).

Raju D. Ch. V., Rajesh R.S. and MishraD.C. (2002). Bouguer anomaly ofGodavari Basin, India and MagneticCharacteristics of Rocks along its CoastalMargin and Continental Shelf, Journal ofAsian Earth Sciences, 21 (2), 111-117.

Reddy CD et al., (2000). Crustal strainfield in the Deccan trap region, westernIndia derived from GPS measurements.Earth Planet Space, 52, 965-969.

Reddy CD, (2001). GPS for crustaldeformation studies: Some case studiesGIS development, 5, 47-150.

Reddy CD, (2001). Error contributors andaccuracy in GPS measurements Ind. Geol.Cong., 235-244.

Singh A.P.(1999). The deep crustalaccretion beneath the Laxmi Ridge in thenortheastern Arabian Sea: the plumemodel again J. Geodynamics, 27 (4-5),611-626.

Singh A.P.(2000). Deep crustal structureof the Narmada-Tapti region. VisakhaScience Journal, 4 (1) 21-36.

Singh A.P., Rao M.B.S.V., ChandrasekherD.V., Vijaya Kumar V., Gupta S.B. andMishra D.C. (2000). Subsurfaceconfiguration of the southern High GradeGranulite terraneinferences fromIntegrated Geological/ Geochemical/Seismic/ Magnetotelluric, Deep Resistivityand Gravity Studies, Published in "TheIndian Mineralogist" (Journal of theMineralogical Society of India), 34 (1),43-45.

Singh A.P. and Mishra D.C. (2002).Tectonosedimentary evolution ofCuddapah basin and Eastern Ghats Mobilebelt (India) as Proterozoic Collision:gravity, seismic and geodynamicconstraints, J. Geodynamics, 33, 249-267.

S ingh B. (2002) . Simultaneouscomputation of gravity and magneticanomalies resulting from a 2-D object,Geophysics, 67 (3), 801-806.

Tiwari V.M. and Mishra D.C.(1999).Estimation of effective elastic thicknessfrom gravity and topography data underDeccan volcanic province, Earth andPlanetary Sci Letters, 171, 289-299.

Tiwari V.M., Rao, M.B.S.V. and MishraD.C.(2001). Density inhomogeneitiesunder Deccan Volcanic Province asderived from gravity data, J .Geodynamics, 31, 1-17.

Tyagi, V.C. (2001). Geodetic andGeophysical Studies in Earthquake ProneAreas in India, Symp." Recent CrustalMovement at Helsinki', Finland, Aug 27-31, 2001.

Tyagi, V.C. and H.B.Madhwal (2001).Geodetic & Geophysical Studies forMonitoring Crustal Deformation inKachchh region of Gujarat, Conf. onSeismic Hazard with particular referenceto Bhuj earthquake, January 26 Delhi Oct.,2001.

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Tyagi, V.C, B. Nagarajan and S.K. Singh,(2002). Geodetic Studies in PeninsularIndia for Monitoring Crustal Deformationusing Global Positioning System (GPS)and Levelling Techniques, Papersubmitted to Department of OceanDevelopment, New Delhi, September,2002.

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GEOMAGNETISM AND AERONOMY

G. S. LakhinaIndian Institute of Geomagnetism, Mumbai

Introduction

During the period 1999-2002, there was aspurt in the research activities related tothe area of Geomagnetism and Aeronomy.India offers a unique geophysical locationfor the investigations of the complexprocesses related to the Earth’s interior aswell as the electrodynamical processesoccurring in the ionosphere andmagnetosphere. Indian scientists havemade use of this situation to investigatesome important problems related to thedynamics of the Earth’s interior, solar-terrestrial relationships and space weatherusing experimental, analytical, andmodeling techniques

Much international collaboration also tookplace during this period to conductexperiments and analyze the data fromequatorial and low latitudes to understandthe electroject and other geomagneticphenomena. There are about thirty centersengaged in research related toGeomagnetism and Aeronomy in India.The present report is based on the materialreceived from those organizations thatresponded to our request to submit theirinput for the National Report for IUGG-2003. Their cooperation is thankfullyacknowledged.

Indian Institute of Geomagnetism,Mumbai

The Indian Institute of Geomagnetism(IIG), a premier research organizationunder the Department of Science andTechnology, is devoted to the study ofGeomagnetism from all possible point ofviews. The research activities of IIG areorganized into three main areas:

ÿ Observatory and Data Analysis(ODA)

ÿ Upper Atmospheric Sciencesÿ Solid Earth Geomagnetism

The main research activities of these threedivisions and the Instrumentation Divisionfor the period 1999-2002 are given below.

Observatory and Data Analysis (ODA)

IIG operates a chain of ten permanentobservatories recording continuousmagnetic variations. Modern absoluteinstruments, Declination InclinationMagnetometers (DIMs) are being used torecord and maintain the stability in thebaseline, which is a crucial parameter incomputing the final absolute values fromvariation data.

The INTERMAGNET system is beingoperated at Alibag and the DIGITAL datais transferred in near real time from Alibagto Colaba. The processed binary data aresent to the Geomagnetic InformationNodes (GIN's) at Boulder, USA andKyoto, Japan within 48 hours of receipt ofdata at H.Q. The data can now be viewedin near real time on the web at the WDC,Kyoto website.

Magnetic observatory at Trivandrum,established in 1957 in the campus ofKerala University, was closed down on30th October 1999. However continuity inthe data is maintained by the GeomagneticObservatory operating at IIG’s EquatorialGeophysical Research Laboratory(EGRL), Tirunelveli. The magneticobservatory at Jaipur was recommissionedin the year 2002. In addition to the DigitalFluxgate Magnetometer, an IZMIRAN-IVvariometer is also set up for analoguerecordings at Jaipur.

Under the newly initiated GeomagneticActivity Forecasting Program, state of theart Digital Fluxgate Magnetometers havebeen installed at Tirunelveli, Pondicherry,Visakhapatnam (east coast station ofIndia) and Jaipur magnetic observatories.The data from these observatories are

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received at H.Q. in near real time and willbe used for geomagnetic data basedresearch and predicting geomagneticactivity, especially from low latitudes asthe contribution of the low latitudegeomagnetic data in assessing themagnetic disturbance parameters isimportant.

Antarctic Geomagnetism

The Institute has been pursuing a vigorousprogramme on Antarctic Geomagnetism.The Institute continues to participate in thesummer and winter expeditions toAntarctica every year. Two of our staffwere selected for the team leadership intwo winter expeditions. Analog as well asdigital instruments record valuablegeomagnetic data. Also a fluxgatemagnetometer and a Riometer recordingthe 30 MHz cosmic radio noise weresimultaneously operated at Maitri to studythe characteristics of ionosphericabsorption caused by magnetosphere-ionosphere particle precipitation. A newexperiment on atmospheric electric currentas a part of the Global Electric Circuit(GEC) study was started at Maitri.

Geomagnetic data based investigationsGeomagnetic data based investigations aredone by the scientists of IIG to understandthe complexities of equatorial electroject(EEJ) and counter-electrojet (CEJ) andsolar quiet (Sq) variations. Magneticeffects of intense solar flare were studiedusing the data from the ten geomagneticobservatories in the Indian longitudesector. The solar flare effect (sfe) asregistered on the magnetogram ismanifested by an enhancement of theionospheric current system existing at thestart of the flare. An equatorialenhancement of H component of thegeomagnetic field due to sfe was found tobe similar to the latitudinal variation ofSq(H) at low latitudes.

It is found that over the last 75 years, atthe location of DAKSHIN GANGOTRI/MAITRI, the total field (F) has dropped atthe rate of about 120 nT per year. Data of3-fluxgate magnetometers operatingsimultaneously at Maitri, Dakshin

Gangotri and Orvin Mountains inAntarctica were analysed for the magneticpulsation with periods between 30 sec. and3000 sec. and interpreted in terms of themobile auroral current systems that driftover the stations. The geomagnetic dataare also used to study the processes ofionosphere-magnetosphere coupling andsubstorm dynamics.

The short-term variability in thegeomagnetic field during the total solareclipse of 11th August 1999 was studiedusing the magnetic observatory chainoperated by IIG and the specialobservations taken at Akola and Baroda inthe path of totality. The gradient of thefield was found to be different in pre-totality and post-totality times. Such typesof gradients were not observed at the sametime on controlled days.

A few sudden commencement greatgeomagnetic storms recorded during thesolar cycle 22 were studied by analyzingmagnetic records from selected lowlatitude Indian stations. Strong daytimeequatorial enhancement in intensity of thegeomagnetic Pc5-6 pulsation duringseveral magnetic storms was observedfrom an array of 5 Indian stations.Magnetic storm of 31st Dec. 1967 and 1st

Jan. 1968 was studied using data ofground based magnetometers andionosonde station in India, Africa andAmerican sectors.

Magnetic data from the Indo-Russiannetwork that was in operation during theInternational Equatorial Electrojet Year(IEEY) have been analysed to study thespatial and frequency characteristics of theequatorial enhancement. The analysisshows that equatorial electrojet acts assimple amplifier that enhances any inputelectromagnetic field by a factor of 3-5.

Triggering of sub storm by isolatedinterplanetary (IP) shocks was studiedusing the data from satellites like, ACE,GOES-8 & GOES-10 and groundmagnetometer data for four selected eventsof 2001. Response of the sudden increasein the solar wind dynamic pressure wasreflected in the ground magnetic records

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as the sudden commencement. Thephenomenon of geomagnetic bays, whichgives important information on the onsettime of substorms, was studied byanalyzing the INTERMAGNET one-minute digital magnetic field data.

Three major solar flare events of the solarcycle 23 were identified to study thecharacteristics of the geomagnetic fieldcomponents at latitudes ranging from theequator to the latitude of Sq focus in theIndian longitude sector.

Upper Atmospheric Sciences (UAS)

Ionospheric and upper atmosphericstudies

Amplitude scintillation on 250 MHz radiosignals recorded at a network of stations inthe Indian sector during the last five yearshave been analyzed to study thecharacteristic features of ionosphericirregularities. Scintillations recorded onthe 250 MHz radio beacon at Mumbai andPondicherry were analyzed to look for thepossibility of field line resonances atequatorial latitudes. Dual frequency datafor fluctuations in the total electroncontent ( TEC ) along the path of GPSsignals to the equatorial station Ancon (1.5O dip), sampled at a rate of 1 Hz, hasbeen used to separate this contributionfrom the slower TEC variations. Atheoretical model, using the transmissionline analogy, has been developed toinvestigate the coupling between the E andF regions through field-aligned currents(FACs).

Spaced receiver observations of amplitudescintillations on a 244 MHz signal, at anequatorial station, have been used to studyrandom temporal changes associated withthe scintillation-producing irregularitiesand the variability of their motion. Thecomputed drift of the scintillation patternshows the presence of velocity structuresassociated with equatorial bubbles in theearly phase of their development. Thepower spectra of the most highlycorrelated scintillations recorded byspaced receivers indicate that theassociated irregularities are confined to a

thin layer on the bottom side of theequatorial F region. In an other study, itwas found that during the high solaractivity period (1989-1991), an increase ingeomagnetic activity suppressed theoccurrence of scintillation activity atTrivandrum and Mumbai stations,whereas the electrojet strength is found tohave no association on the occurrence ofscintillations.

Space weather affects the distribution ofplasma in the ionosphere andplasmasphere through which radio wavesused for communication and navigationpropagate. On some occasions, only largescale (>10 km) structures in thepropagation medium are encountered bythe radio waves, while at other times smallscale variations in ionospheric electrondensity give rise to scintillations on trans-ionospheric radio waves.

The occurrence of L-band scintillations ontrans-ionospheric signals, due to plasmadensity irregularities in the nighttimeequatorial ionosphere, may have asignificant impact on the use of GlobalPositioning System (GPS) signals fornavigation, particularly in the presentphase of solar cycle maximum. Usingspaced receiver observations of a 250MHz signal at a location close to theequatorial anomaly crest, it is seen that thepresence of strong L-band scintillations isclosely associated with large decorrelationbetween the 250 MHz signals recorded byspaced receivers. This generally happensin the pre-midnight period when equatorialplasma bubbles rise rapidly to the topsideof the F region and become highlystructured.

An airglow monitoring station has beenoperating at Kolhapur to study variouscharacteristics of F-region irregularitiesusing an all-sky camera, tiltingphotometers, scanning photometer andVHF scintillation experiment. A largenumber of equatorial ionospheric plasmabubbles or depletions are characterized bythe development of strong equatorialionization anomaly. Analysis of theairglow data obtained during the ISTEP-IIcampaign period of March 12-21 and

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April 10-22, 1999, showed north-southaligned intensity depletions, which are theoptical signature of large scale ionosphericF-region plasma bubbles, on most of thenights.

The night airglow observations werecarried out from Kolhapur (16.80 N,74.20E) and Panhala (17.0 0N, 74.2 0E),India which is situated at 3200 feet abovethe sea level during February, 2001 usingtilting photometers (OI 630 nm and OH)and an all-sky imager on clear andmoonless nights. From these data, thegravity waves were detected, for the firsttime in Indian latitude region, showingperturbation in density in the mesosphericregion (80-100 km) while the waves werepropagating vertically from tropopause tothe upper atmosphere. An intenseenhancement in OI 630 nm intensity wasobserved during the main phase of thegeomagnetic storm on the night of 7th

February 2000.

The importance of studies of ionosphericplasma irregularities grew because of theirstrong influence on ionospheric and trans-ionospheric communications. The bubblesobserved during the different phases ofgeomagnetic storms show unusualstructures (bifurcated and twisting). Thecontinuous movement of the high risebubbles across the zenith gives rise tostrong VHF scintillations.

An analysis of low order mode couplingequations is used to describe the nonlinearbehaviour of the Rayleigh-Taylor (RT)instability in order to understand thegeneration of equatorial spread-F. Thenonlinear evolution of RT instability leadsto the development of shear flow. It isfound that there is an interplay betweenthe nonlinearity and the shear-flow whichcompete with each other and saturate theRT mode both in the collisionless andcollisional regime.

The characteristics of geomagneticpulsations undergo appreciable changes asthey pass through the ionosphere. Thesechanged properties at the low andequatorial stations are distinctly differentfrom those at the high latitudes. It is

found that polarization directions of PC3-4(period 10 to 100 seconds) pulsationchanged during the counter electrojet time.The amplitude of these pulsations isenhanced by equatorial electrojet. Theresponse of magnetospheric transversemodes to the solar wind dynamic pressureinduced oscillations of the surface currentflowing at the magnetopause has beencomputed based on the technique ofspectral representation of the Green'sfunction.

There are very few phenomenon in theupper atmosphere that are as sensitive tothe strength and distribution of the earth'score field as the equatorial electrojet. TheOersted initial field model along with theearlier IGRF models have been used toprovide insight into the secular changes inthe global patterns of the position andstrength of the Equatorial Electrojet (EEJ).

The Equatorial Geophysical ResearchLaboratory (EGRL) at Tirunelveli madegood progress during this period. Thepartial reflection (PR) drifts at 98 kmmeasured by the medium frequency (MF)radar are shown to have the combinedeffects of mesospheric winds and theequatorial electrojet. Observations ofmesospheric winds in the altitude region84-98 km with the PR radar at Tirunelveliand the ground-based geomagnetic datafrom the low latitude Indian sector havebeen used to identify the signatures of thequasi-2-day (QTD) planetary waves in theequatorial electrojet (EEJ). It is found thatthere is a reasonable correlation betweenoccurrence times of the quasi-2-dayoscillation in the EEJ strength and themesospheric winds.

Second partial reflection radar at theShivaji University Campus, Kolhapurbecame operational. The two radars atTirunelveli and Kolhapur constitute aunique pair for studying structure of tidalmode, planetary scale oscillations andgravity waves. Important results on thecharacteristics of the mesospheric 3.5-dayultra-fast Kelvin waves, which carryeastward momentum into the upperatmosphere, were obtained and the resultspresented in the PSMOS workshop. It is

22

planned to set up some new atmosphericelectricity experiments.

Examination of the Tirunelveli PR radardata reveal a relationship between thetidal characteristics and the occurrence ofafternoon counter electrojet (ACEJ). Aclear anti-correlation is seen between theafternoon electrojet strength and theamplitude of the semi-diurnal tide in thesolstitial months of June and July, 1995.

Magnetospheirc Phenomena

Boundary layers, commonly encounteredin space and astrophysical plasmas, arethe site where energy and momentum areexchanged between two distinct plasmas.Broadband plasma waves spanning afrequency range of a few mHz to 100 kHzand beyond have been observed in theEarth’s magnetopause boundary layer, theJovian magnetopause boundary layer, theplasma sheet boundary layer, and theEarth’s polar cap boundary layer. Themost intense waves are detected coincidentwith the strongest magnetic field gradients(field-aligned currents). The rapid pitchangle scattering of energetic particles viacyclotron resonant interactions with thewaves can provide sufficient precipitatedenergy flux to the ionosphere to create thedayside aurora at Earth and a weak high-latitude auroral ring at Jupiter.

Polar cap boundary layer waves areELF/VLF electric and magnetic wavesdetected on field lines just adjacent to thepolar cap. Intense waves are present atthis location essentially all (96%) of thetime. The wave latitude-local timedistribution is shown to be the same as thatof the Feldstein auroral oval, a distributioncentered at ~75o at local noon and ~65o atlocal midnight. The most intense wavesare detected coincident with the strongestmagnetic field gradients (field-alignedcurrents).

A fully electromagnetic linear theory forthe generation of broadband plasma wavesobserved in the low latitude boundarylayer by POLAR has been developed. It isshown that electron acoustic waveinstability can offer a possible generation

mechanism for the broadband electrostaticnoise (BEN) observed in auroralacceleration region, plasma sheetboundary layer, and polar cusp region. Atheoretical model for the large amplitudeelectrostatic ion – cyclotron modes in anauroral beam – plasma system isdeveloped. The numerical solutions of thenon-linear evolution equation couldreproduce several essential features of theobserved waveform by FAST and POLARsatellite.

Recent exciting high time resolutionresults coming from Geotail, Viking, Polarand FAST show that broadband plasmawave emissions consist of bipolar andmonopolar solitary structures. A modelfor the nonlinear evolution of electron-acoustic waves into solitary structures hasbeen developed. The predicted propertiesof the electron acoustic solitons are foundto be in good agreement with theobservation of spiky electric fieldstructures by the spacecraft. Further, ananalytical model of the coupled nonlinearion cyclotron and ion-acoustic waves hasbeen developed to explain the strong spikywaveforms in the parallel electric field inassociation with ion cyclotron oscillationsobserved by FAST satellite.

Interplanetary medium

A direct mechanism for the generation ofwaves in the intermediate frequenciesbetween the water-group and the protongyrofrequencies in cometary environmentsis suggested in an unstable wavelengthband when the solar wind is sufficientlymass-loaded by cometary material. Themirror mode structures at cometGiacobini-Zinner are detected in a regionjust adjacent to the magnetic tail, and theyhave scale sizes of ~ 12 H2O group ioncyclotron radii. It is shown that nonlinearevolution of Alfvén waves, propagating instreaming solar wind plasma with non-uniform densities and inhomogeneousmagnetic fields, is governed by themodified derivative nonlinear Schrödinger(MDNLS) equation.

Analysis of Ulysses magnetometer datarevealed the presence of magnetic field

23

decreases (MDs) over the heliosphericpolar regions. The MDs have minimumspatial scale sizes of 25 proton thermalgyroradii, and are typically bounded bytangential or rotational discontinuities.Charged particle interactions with theMDs can lead to particle guiding centerdisplacements and hence particle cross-field diffusion.

It is shown that interplanetary shocksimpingement upon the Earth’smagnetosphere can cause dayside near-polar auroral brightenings. The aurora firstbrightens near local noon and thenpropagates toward dawn and dusk alongthe auroral oval. Significant charged-particle precipitation occurs in the daysideauroral zone during and after these shockimpingements. The total energy depositionrate may be considerably greater (~ anorder of magnitude) than nightside energyrates.

Simulation studies

The resistive hydromagnetic equations aresolved numerically in a two dimensionalbox to simulate the dynamics ofgeomagnetic tail during substorm eventsby applying the Flux Corrected Transport (FCT ) code. Three different widths for theinitial current sheet are investigated. Forwider current sheet the reconnection startslater than the case of narrower currentlayer. It is found that pre-substormearthward flows deduced from satellitedata could be explained by the widercurrent sheet case. However, thesesimulations are able to reproduce the onsetof reconnection and formation ofmagnetic island - like structures calledplasmoid as observed.

Solid Earth Geomagnetism (SEG)

Wide Band Magnetotelluric studies ofIndian Lithosphere

Magnetotelluric studies in the Himalayanregion have shown an anomalously highconductivity in the Indus suture and theTso Morari dome extending from theshallow levels to depths of about 25 km.Studies in the granite-greenschist region of

the Dharwar craton have delineated a highconductive zone beneath the west Dharwarcrust at depth of about 60 km and beyond,corresponding to the lithospheric mantle.Studies over the NW Indian shield ofRajastan have delineated clear signaturesof the Bundelkhand granitic masssubducting beneath the Aravalli blockalong the great boundary fault.

Deep Electromagnetic Imaging of theIndian Shield

A new program of long periodmagnetotelluric (LMT) measurements hasbeen initiated at the Institute to determineand establish deep electrical characterbeneath cratons, mobile belts, andcollision zone. The LMT studies across theDharwar craton have revealed lithosphere-asthenospheric boundary at a depth of 220km confirming well with the heat flow andseismic data. The studies in the NWHimalaya have provided new insight onthe depth extent of the high conductivityzone beneath Tso Morari and shownevidence of anisotropic layer at a depthgreater than 100 km LMT survey acrossthe thermally active Kutch rift to decipherdeep geodynamics and possible thermalmanifestation of Deccan volcanism alongthe western continental margin, hasbrought out evidence on the presence of amoderately conducting layer between 10-17 km.

An electrical conductance model has beenevolved to account for the geomagneticinduction anomalies in peninsular Indiaand Bay of Bengal, The model showedthat South India Offshore ConductivityAnomaly and its coincidence with theseismic low velocity zone and MAGSATlow magnetization anomaly, all centerednear the southern tip of India, indicatethese geophysical anomalies to be themanifestation of the interaction of theMarion plume with Indian Lithosphere.The nature of conductivity distributionbeneath the Nintyeast and 85o E ridges,inferred from transient geomagnetic datarecorded by ocean bottom magnetometer,does not favour presence of partial meltbut does not rule out localized magmaticintrusion into the crust.

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Studies of Indian Lithosphere ThroughMagnetic Anomalies

Aeromagnetic data over Peninsular India(8 to 24 degrees N) have been analysed forthe first time to throw light on the varioustectonic blocks of the region. From theaeromagnetic anomaly, its analyticalsignal and Euler solutions, the subsurfacestructure of the region is brought outwhich redefine the edge of the craton andthe tectonic elements of the area especiallyin regions with large surface cover. TheCharnockites and the iron ore series areidentified as the main magnetic sources. Avery striking feature is the long arcuateshaped shear that extends for over 1000km in Central India across the Peninsulafrom west to east to mark the edge of theEastern Ghat block, the Bastar craton andpossibly the Dharwar craton. This hasbeen termed as the Main Peninsular shear.Palaeomagnetic studies

The Palaeomagnetism Group has beenvery active in establishing the precise age,duration and extent of the Deccan Trapsmagmat i sm by ca r ry ing ou tpalaeomagnetic studies on the dykesswarms intruded into the Deccan basaltflows along the west coast and also in thecentral part of the Deccan volcanicProvince. The results on the Deccan Trapsassociated dykes indicated that the Deccaneruptions took place around 65 Ma backwith the span of less than 1 Ma andaffected the entire Bagh Group sedimentsof Narmada region. Palaeomagneticinvestigations have been successfully usedin differentiating the dykes of DharwarCraton based up on their characteristicremanent directions. Precambrian dykes ofDharwar Craton were distinguished into 5generations, viz., 1100 Ma, 1650 Ma, 1800Ma, 1900 Ma and 2300 Ma, and traced theapparent movement of the Dharwar Cratonduring 2000 Ma to 2300 Ma by fitting thepolar wander curves. Palaeomagneticstudies on Oddanchatram anorthosites,Tamilnadu indicated that this body wasemplaced during the Eastern Ghat orogeny(~1000 Ma) and may be seen as thewestern extension of the string of massif

type anorthosites in the Eastern GhatMobile belt.

The low field AMS studies on the clasticsediments of a 5.5 km thick section in theAssam-Arakan basin yielded well definedmagnetic lineation directions which areparallel to the bedding strike directions,suggesting the sediment supply to thestudied area was from the Mishimi Hillmountains, which rests at the northeasternmargin of the studies section.

Environmental mineral magnetism inpalaeoclimate and environmentalreconstructions

The Institute has established a group forenvironmental studies that has made rapidgrowth and generated quality data on theIndian lake, delataic and deep seasedimentary records. Sedimentary lithounits, grain size parameters and magneticsusceptibility differences from fourmangrove regions namely Mahanadi,Krishna, Godavari and Cauvery haverevealed marked changes in recentclimate, i.e. high hematite content due towarm climate conditions around 2000 calyr BP (before present). Mineral magnetismof Iskapalli lagoonal sedimentsdocumented a drier climate (~ reducedmonsoons) leading to more frequent firedisturbances around 3700 cal yr BP.Global significance of rapid climateoscillations during the last glacial period(~ 70 ka) over the continent is inferred forthe first time from a newly generatedcontinental record from western tropicalIndia using variations in percentages ofgrain size, magnetic susceptibility,carbonates and minerals.

GPS studies in estimating the strainfield

Many GPS campaigns have beenundertaken in various earthquake pronezones of India viz. Western Maharashtra,Bhuj region of Gujarat, Chamoli region inUttaranchal, North Eastern Indian region.Magnitude of the average horizontalvelocity of Deccan trap region in ITRF96is 51 mm/yr in N47o E. The estimated

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dilatational strain is about 0.4 microstrain/yr in average. An extensional strainregime is observed along the west coasttranscending into a region of compressivestrain towards the interior of the shieldarea. The extensional strain regimecoincides with the West Coast GeothermalProvince. The Murbad region in Thanedistrict of Maharashtra is under E-Wcompression and N-S expansion regime.Intra-plate movements are detected aroundAmberji. The East-West, North-south andvertical components of the baseline Lodai-Ratanpar (passing through the epicentralarea) show no co-seismic displacementsassociated with 26th January 2001 BhujEarthquake. N-S compressional strain ofabout 0.1 micro strain/yr found in betweenRatanpar and Dhamdkapir

Instrumentation Division

A PC controlled PPM and a new BarkerCoil System , for a newly designed VectorProton Magnetometer were fabricated.The PC Controlled Proton magnetometerhas a sensitivity of 0.1 nT and can be usedin Magnetic Observatories for Calibrationof other Magnetometers.

A portable/field use microcontroller basedProton Magnetometer that works onbatteries and has internal memory to storedata was designed. This magnetometerwas tested against internationalcommercial models in a Symposiumorganized by IAGA at South Africa. Themodel showed a good match with thestandard at Hermanus MagneticObservatory at South Africa.

The Indian Institute of Astrophysics,Bangalore

The regular sunset enhancement of upwarddrift of equatorial F region plasma isobserved to be abnormally large on certainquiet days (Sp. £ 5) as manifested by ananomalous increase of F region height.It is found that on the days with anunusually large dusktime increase of Fregion height over Kodaikanal, the diurnalprofile of the equatorial electroject (EEJ)strength is severely distorted (with a shiftin some cases, of Sq(H) phase from the

usual time interval, characteristic of theabnormal quiet days, AQD0 withenhanced EEJ conditions in the postnoonperiod (13000-1600 LT). This isaccompanied, near the magnetic equator,by higher values of F layer peak height(hpF2) and lower values of peak electrondensity (f0F2) in the early evening period(1600-1800 LT), compared with themonthly median/quiet day mean values.These changes in EEJ and hpF2/f0F2 areconsistently seen in all cases studied. Weinterpret that the perturbations in plasmadensity distribution of equatorial F region,increase the thermospheric zonal wind andits local time gradient as well as the ratioof f lux-tube-integrated Pedersenconductivity of the F to E region. Thesemodifications just prior to sunset, promptan efficient F region dynamoaction,resulting in the observed abnormally largedusktime increase of F region height. Thestudy strengthens the view that thepostsunset behaviour of the equatorialionosphere is sometimes predetermined bythe properties of the thermosphere-ionosphere system in the early eveninghours.

In-depth case studies are made tocharacterize the features of the dynamicsof the ionosphere-thermosphere systemthat favour the occasional postsunset onsetof range spread-F at Fortaleza, Brazil (diplatitude 1.8 S) during the June solstice.This is the season in which frequencyspread F is typically seen while rangespread F is remarkably inhibited atFortaleza. The onset of range spread-Fstudied is thus an exception to the rule andhas relevance to the topic of day-to-dayvariability of equatorial spread F of muchcurrent research. It is found that animpulsive and large F layer vertical drift(20 – 60 m/sec) prevails in the earlyevening hours on days of range spread F,in contrast to the average pattern of aslowly varying vertical drift of moderateamplitude (15 – 18 m/sec). There is nosignificant change in the pattern ormagnitude of low-latitude meridionalwinds between the days of range andfrequency spread F at Fortaleza. Thissuggests that meridional wind variabilitydoes not play a important role in creating

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favorable conditions for range spread F ona day-to-day basis in the June solstice.The prerequisite for the occasionaloccurrence of range spread F is thepresence of an impulsive and large verticalplasma drift, a condition favourable fordestabilization of the bottomside F layerthrough Rayleigh-Taylor (RT) instabilitymechanism. Evaluation of the generalizedRT growth rates for the specific eventssupports the interpretation. Theanomalously large F layer vertical driftseen on range spread F days is associatedwith moderately disturbed geomagneticconditions as well as quiet conditions.Short-lived prompt electric fielddisturbances due to auroral substormactivity are ascertained to be the cause ofthe large F layer uplifts under disturbedgeomagnetic conditions.

Electrodynamic Coupling of HighLatitude-Low Latitude Ionospheres

The geomagnetic and ionosphericmanifestations of DP2 activity thatoccurred on April 7, 1995 were studiedusing the high time resolutionmeasurements of F layer vertical drift, Vzover Kodaikanal, India with the HFDoppler radar and magnetometer data ofIMAGE network in Scandinavia and atAlcantara, Brazil. Quasi-periodicfluctuations in dusktime (1730-1900 LT) Flayer vertical drift occurred overKodaikanal coherent with DP2 typemagnetic fluctuations (period ~ 25minutes) at the dayside dip equator(Alcantara) and auroral/subaurorallatitudes (IMAGE network stations). TheDP2 – associated vertical plasma drifts areupward (amplitude 13-33 m/sec) implyingeastward electric field disturbances. Thesefirst ever observations of ionosphericplasma motions due to DP2 electric fieldsat the duskside dip equator are inagreement with the two-cell equivalentcurrent system proposed for Dp2. Theresults demonstrated that the transientcomponent of the magnetospheric electricfield responsible for DP2 magneticfluctuations penetrates, through the polarionosphere on the duskside as on thedayside. An additional observation is thatthe amplitude of the plasma drift

fluctuations increase towards the nightside– suggesting a contribution of sunsetelectrodynamics to the observed signatureof DP2 electric fields.

The F-layer of the ionosphere above thedip equator is known to develop “spread –F” conditions around midnight duringsummer. Earlier, this was thought to bedue to instabilities manifested as anincrease in the mean height of the F-layer.An analysis of the ionogram database ofKodaikanal showed however that the F-layer elevation occurs irrespective ofspread – F conditions. This findingrequires a drastic revision of the earlierideas about the phenomenon.

The first ever evidence for DP2 electricfield in the midnight dip equatorialionosphere was obtained from carefulanalysis of quasi-periodic fluctuations inF-layer vertical plasma motions recordedby the HF Doppler sounder at Kodaikanal.Complex patterns of the latitudinalvariation of the solar flare effect ingeomagnetic field was seen from a studyusing data from the Indo-USSR chain ofmagnetometer stations.

The STP group participated in theobservational equatorial spread – F (ESF)campaign held in April 1998 and March1999 under the activities of WorkingGroup (WG) 3 of Indian Solar TerrestrialEnergy Programme (I-STEP.)

The STP group of the Institute participatedin the Equatorial Spread F ( E S F )campaign held during April 1999 underthe I-STEP. Regular data acquisition inthe monitoring mode continued with theexperimental facilities (IPS42 digitalionosonde, HF Doppler Radar andMagne tome te r ) a t Koda ikana lObservatory.

A comprehensive study of the ionosphericstorm of November 4, 1993 in the Indianequatorial region was undertaken in theInstitute because of the absence hitherto ofan assessment of the response ofequatorial upper atmosphere to thismagnetic storm. The study, based on datafrom the ionosonde and magnetometer

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networks in the country, brought to lightseveral new facets of the storm-timebehavior of the equatorial ionosphere,indicating, in particular, a significantelectrodynamic coupling between high –and low latitude ionosphere.

Work is continuing in the Institute on theinter-relationships between solar wind,magnetosphere and ionosphere. Theglobal manifestation of the waveform ofthe geomagnetic storm suddencommencement (SC) of November 18,1993 has been evaluated using high timeresolution data of several magnetometernetworks coupled with HF Doppler Radarmeasurements at Kodaikanal. The workrevealed that the dip equatorial appearanceof the preliminary reverse impulse (PRI)of the SC deviated quite significantly fromthe pattern established by previousstatistical studies as well as the onepredicted by currently available theoreticalmodels of SC.

Institute’s scientists are also involved indetailed study of the effects of meteorshowers on the ionosphere. In particular,the effect of Leonid meteor showersduring the years 1996 through 1998, onthe characteristics of sporadic-E layers atequatorial latitudes, has been studied usingdata of rapid ionospheric soundings atseveral stations in the country. The resultsshowed an increase in the occurrence of Eslayers at altitudes in the range 100-140 kmthroughout the equatorial region at thetimes of peak shower activity. The findingunderscores the need for further studies toascertain the origin of the observedchanges in Es behavior, in particular therelative roles of deposition of metallic ionsdue to shower activity and the physicalmechanism(s) that cause ion-convergenceand lead to Es layers.

Case studies are done to investigate thenature of transient disturbances (duration ~2 hr) in the equatorial electrojet currentduring the different phases of isolatedsubstorms triggered by directional changesin the interplanetary magnetic field, IMF.Data from the Indian magnetometernetwork spanning the dipole latitude range1.2 S-13.5 N are used. A positive bay-like

perturbation is found to prevail during thegrowth phase of the substorm, followed byconspicuous negative-by perturbationprecisely with the onset of the expansionphase. The amplitude of both the positivebay and the subsequent negative bay ismarkedly enhanced in the equatorialelectrojet region compared to stationsoutside the electrojet. This repeatableresponse pattern is strongly indicative ofthe occurrence of short-lived disturbancesin the ionospheric zonal electric field withboth the growth phase and expansionphase onset of isolated substorms, afeature that has never been reportedbefore. The evidence electric fieldperturbations are suggested as signaturesof prompt penetration electric fieldsassociated with rapid changes inmagnetospheric convection brought aboutby swift transitions in IMF Bz/Bycomponents during substorms.

Solar wind-magnetosphere-ionospherecoupling

A halo coronal mass ejection (CME) leftthe Sun around 1054 UT on July 14, 2000and the CME-driven shock wave impactedthe Earth’s magnetosphere at 1437 UT onJuly 15, 2000 and produced a severemagnetic storm the largest such event innearly a decade. This magnetic stormwhich has come to be popularly known asthe Bastille day storm. IPS42 digitalionosonde measurements at Kodaikanal,Waltair and Trivandrum showed ananomalous and extremely rapid decreasein F layer height (maximum value close todip equator, 215 km/hr) simultaneously atall the stations around local midnightduring the storm main phase on July 15,2000. Careful analysis of the geomagneticand ionospheric data showed that theabnormal midnight descent of equatorial Fregion indicative of a short-lived westwardelectric field disturbance (peak amplitudeª mV/m) is due to prompt penetration ofconvection electric fields associated withimpulsive injections of the magnetosphericring current. This is the first timeevidence for the occurrence of such a largeamplitude westward penetration electricfield around local midnight, in anenvironment under the influence of

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eastward electric fields due to the‘disturbance dynamo’ mechanism. Thecase study highlights the profound mannerin which the equatorial F region plasmadynamics can get modified during themain phase of severe magnetic storms.This result has important practicalimplications for telecommunications.

Ionospheric Oscillations

Global scale oscillations in the earth’smagnetosphere-ionosphere system werefound to follow the impulsive increase inthe solar wind dynamic pressure from 1.5nPa to 4.0 nPa over the interval 1002-1008UT on November 9, 1997. This evidencewas obtained from simultaneousmeasurements with multiple spacecraftand groundbased instruments. Themagnetospheric compression affected bythe solar wind pressure pulse generateddrift echoes in the outer radiation zone,with the strongest echoes from electrons inthe energy range 100-200 keV. Groundbased magnetometers registered periodicenhancements of ionospheric currents witha period of 60-70 min, the same as of thedrift echoes. The study suggests a newsource of ionospheric oscillations inassociation with magnetospheric driftechoes generated by solar wind pressurepulses.

Storm Sudden Commencements

The geomagnetic storm suddencommencement (SSC) of July 8, 1991 wascharac te r ized by a reduct ion(enhancement) of X/H-component atmidlatitudes in the noon (midnight) sectorin the 1-hr period after its start at 1636UT. This distinctive feature was seen evenafter accounting for the effects ofChapman-Ferraro currents in themagnetopause. The HF Doppler radarmeasurements of F region vertical plasmadrift over Kodaikanal revealed that, overthe same 1-hr period after the SSC on July8, 1991, an eastward electric fielddisturbance grew up and decayed near thepremidnight magnetic equator. Theeastward electric field is interpreted as thesignature of the penetration of the dawn-to-dusk electric field associated with an

enhancement of region-1 field-alignedcurrents (FACs) driven by the solar wind.

Developmental work

Preparations are nearing completion forthe installation of the DMI digital fluxgatemagnetometer as the replacement for theaged La Cour Variometer which has beenin round-the-clock operation inKodaikanal Observatory since 1949. TheDMI fluxgate system is on par with IAGAstandards and provides geomagnetic datawith high sensitivity and time resolution toaddress several problems in STP that wasnot possible before.

National Physical Laboratory, NewDelhi

SROSS-C2 satellite RPA results:

Retarding Potential Analyser (RPA)aeronomy payload on board SROSS-C2Indian satellite, which was launched inMay 1994 remained in orbit till July 2001thereby covering the period from solarminimum to solar maximum. It generatedhuge amount of data over the Indianregion at F region heights from 400 km to620 km. during this period. Some veryinteresting results have been observedduring the mission. During high solaractivity there is a occurrence of very largescale plasma density depletions at F regionheights during pre-midnight hours. Thesedepletions were found to be 3 to 4 decadesdown as compared to normal densities andcontain large latitudinal gradients. Smallerscale irregularities are also foundembedded within such depletions (Garg etal., 2003). The results on temperatures anddensities showed some very interestingresults during magnetically disturbedconditions, Electron temperature showedsubstantial rise and latitudinal variationduring such events. Leonid meteor showerevents during 1998 & 1999 wereintercepted by the payload. This showedpresence of heavy metallic ions (Fe+)during meteors.

GPS observat ions for TECmeasurements

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Observations of total electron content(TEC) of the ionosphere were carried outfor the first time at the Indian stationMaitri in Antarctica from Jan. 12, 1998 toFeb. 5, 1998 during 17th Indian scientificexpedition to Antarctica. For this purposesignals from Global Positioning System(GPS) orbiting satellites were monitored.A software for deriving TEC from GPSobservations has been developed at NPL.The values so derived for Maitri do notshow large diurnal variations, however thesignatures of large scale disturbances areseen superimposed on the diurnalvariations of TEC.

A new software has been developed whichestimates the Faraday rotation suffered bythe em wave at 6.6 GHz from sea surfaceto the orbiting satellite at a height of 800km. above the earth based on total electroncontent observed by GPS satellites. In thisscheme GPS TEC is used to optimize theIRI model and then IRI model is used toget faraday rotation.

Ionospheric Scintillations

Signals from FLEESAT satellite weremonitored to study the effects ofionospheric irregularities on transionospheric propagation. The data wasanalysed to study the role of neutral windsand electric fields on generation andsustenance of equatorial ionosphericirregularities. The results have shown theimportance of electric fields as evidencedfrom ionospheric heights variations at thegeomagnetic equator in producing thescintillations at a location like Delhi. Thestudy was also taken up as part ofnationally coordinated program onequatorial ionospheric irregularities.Observations have also been started at twosatellite earth stations Chengleton (12.7O

N, 79.9O E) and Sikanderabad (28.5O N,77.7O E) at 4 GHZ. These observationswere carried out using C-band pilot carrierof Thaicom geostationary satellite at 94O

E. A study conducted using Sikanderabaddata showed that there was goodcorrelation between the day timeequatorial electrojet strength and nighttimescintillation intensity.

Anomalous Ionospheric ElectronTemperaturesStudy conducted using electrontemperature data from HINTORI satellitehas revealed certain anomalous variationsin the ionospheric electron temperatures at600 km altitude by way of, exceptionallylarge increases as compared to backgroundvalue in ± 30o latitude range. Theseionospheric temperatures enhancements(Ten) have been observed in a wide rangeof longitudes including the Indian zonewith distinct seasonal and local time bias.On a large no. of occasions they have beenfound to occur on either side of thegeomagnetic equator coinciding with thewell known equatorial ionisation anomaly.The results are explained in terms of zonalwinds, winter anomaly in electron densityand electrodynamic drifts (Dabas et al.,2000). The RPA payload data fromSROSS-C2 satellite also supportsHINTORI observations.

Improvements in IRI

About 1500 electron density (Ne) profilesobserved with the Arecibo IncoherentScatter Radar were used to obtain thethickness parameters of the bottomside Flayer (B0 and B1 parameters) by fitting theobserved profiles to the IRI profilefunction. The relative between the best fitprofiles and the observed IS profiles werealso examined. The error was found to bevery large during the day especially attimes when the F1 layer was present whichhappened for about 30 % of the totalpopulation. The B0, B1 values obtainedfor the remainder 70 % of the casesshowed large variability and were differentfrom the IRI model values. The B0, B1were modelled and suitable changes weresuggested to be included in IRI model(Mahajan and Sethi, 2000; Sethi et al.,2000; Sethi and Mahajan, 2002) . Thestudies were carried out on the variabilityof equivalent slab thickness.

The studies have been made on foF2 for ano, of stations for period from IGY to1990. This data was obtained in the formCDs from World Data Centre, Boulder. Itwas revealed from these studies that thenoon time foF2 shows a linear variation

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with sunspot no. (R12) at mid-latitudes.However, at low latitudes it is no morelinear at high values of R12.

The comparison of IRI model values withobtained for Delhi using digital ionosondeshows a fairly good agreement withobserved median foF2 values for thedaytime, during all the seasons.Discrepancies between the two existduring nighttime, when the percentagedeviations of the IRI model with respect toobserved values fluctuate between 10 to25 % especially during winter and equinoxmonths. This digital ionosonde facilitywas established in 1999 at NPL, NewDelhi.

Rain Attenuation Studies on GHz radiolinks

To study the effect of rain on microwavesignals at GHz frequencies, experimentsare being conducted to derive (a) raincharacteristics using an X-band radar ofthe Indian Meteorological Departmentlocated at Kolkatta, (b) rain attenuation bymonitoring simultaneously a LOS radiolink operating at 18 GHz and (c) raincondition by mounting rain gauges atnearby locations. The horizontal andvertical extents of rain cells were deducedfrom radar reflectivity measurements. Thelink was operating between Sonarpur andJadavpur covering a distance of 8 km. Thesignals were attenuated by as much as 18dB even under moderate rain fallconditions of 55 mm/hr. intensity. Basedon the observations, rain intensity vs rainattenuation curves have been obtainedwhich can be used for designing highreliability links at frequencies > 10 GHzwhich are capable of large datatransmission rates.

RWC AND Forecast services

Short term forecasting and data exchangeactivities of Indian RWC operating fromNPL is a continued effort. Forecasts onsolar and magnetic activities wereprovided to a no. of user agencies IndianNavy, Space, IMD etc. Spatial ionosphericpredictions were also provided to theIndian Defence Services to aid in planning

of HF links. NPL has also been providingHF prediction for links operating in certainstrategic region to Indian Army and AirForce.

Prediction of the size of cycle 23 usingMultivariate relationships

A new technique based on multivariateanalysis is developed for the prediction ofthe size of maximum amplitude of presentsunspot cycle 23. The importance of thetechnique lies in its ability to predict thesize of forthcoming cycle even before thestart of the cycle that was not possiblewith traditional statistical techniques. Theno. Of geomagnetic disturbances atselected times in the declining phase ofcycle 22 are used as precursor to predictthe size of the cycle 23. The observedvalues are found to be within 5%. Thetechnique has predicted the size of presentcycle 23 to be 152.

Planetary Ionospheres

The aeronomy experiments on the PioneerVenus Orbital (PVO) established threecharacteristic features of the nightsideionosphere of Venus, (1) the disappearingionospheres (2) the large spatial/temporalvariability of ion densities and (3) theplasma holes. The studies on thetemporal/spatial ion density variability andthe plasma holes, were carried out byanalyzing O+ density profiles measured bythe ion mass spectrometer experiment onthe PVO. It was found that most of thevariability in the central nightsideionosphere was related to PSW which wasseen to control the O+ peak density andthe height of the nightside ionopause. Theplasma holes were found to occur abovethe nightside ionopause when PSW wasgenerally moderate. It was demonstratedthat there were not real holes in the mainionosphere but were ionospheric structuresseen above the nightside ionopause. Theplasma in these structures was generallyfound to be disturbed and it is proposedthat the source of these structures is theplasma clouds/ detached plasmatransported from above the daysideionopause. The strong radial (sunward/anti-sunward) magnetic fields, which have

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been reported to exist in the holes, werequiet similar to the ones, which weregenerally seen in the nightside ionopause.

Centre for Earth Science Studies,Tiruvananthapuram

Radioactivity and Atmosphericelectrical conductivity:

Simul taneous measurements ofradioactivity using a gamma ray intensitymeter and atmospheric electricalconductivity using a Gerdien condenserwere made in the south-western coast ofIndia, a region of one of the world’srichest radioactive deposits. Themeasurements were used to relate thestrength of radioactivity and atmosphericelectrical conductivity. The data set wasused to derive the effective recombinationcoefficient. The derived values agree withthe model values. Thus, qualitatively andquantitatively the effect of radioactivity inenhancing atmospheric electricalconductivity has been established. It alsopoints to the fact that enhancedconductivity can be used to identifyradioactive deposits.

Distribution of currents in an abnormalEquatorial Electrojet

A number of rocket magnetometermeasurements of the Equatorial Electrojet(EEJ) have been carried out from Thumba,India. Most of the flights were conductedon quiet days close to noon when theelectrojet strength was very high. At thetime of these flights, the geomagnetic fieldvariations at Thiruvananthapuram (a EEJstation) were larger than those at the non-EEJ station like Alibag. However, thegeomagnetic field variations were quiteunique at the time of a launch of aparticular flight. The vertical distributionof current measured in this flight iscompared with the average profileobtained from the results of a number offlights from Thumba, India. It is observedthat on a day when the geomagnetic fieldvariation in the H-component atThiruvananthapuram is very close to thatat Alibag, the vertical extent of the

electrojet current seems to have beenreduced.

Raindrop size distribution atThiruvananthapuram

Raindrop size distribution was measured atThiruvananthapuram using a Joss-Waldvogel type disdrometer. Two types ofdistribution were observed. Much of therainfall showed distributions similar to thatof the Marshall-Palmer (MP) model, N(D)= N0*exp(-_D) with _ = 4.1 R-0.21, where Ris the rate of rainfall, N(D) is the numberper cubic metre of drops of diameter D,and N0 corresponds to the asymptoticvalue for the number of drops of zerodiameter. In certain particular instances,the distribution deviated significantly fromthe MP model. Here, better fits wereobtained with the gamma distributionfunction, particularly for the drops aboveabout 0.5 mm diameter.In subsequent analyses, the lognormalfunction was fitted to the drop sizedistributions, and good fits were obtainedin all cases. The lognormal fit uses threefit parameters that can be related to thesize distributions, namely the total numberof drops, N, the geometric mean, xg, andthe standard geometric deviation, s. Theseparameters were found to depend on therate of rainfall. This is being carried outunder a programme sponsored by theDept. of Science & Technology, Govt. ofIndia.

Study on the widespread “colour rain”phenomenon

The state of Kerala, India, experiencedseveral instances of coloured rainfallduring the months July to September 2001.Rain samples were collected from a fewsites and the detailed analysis was done atone site (Changanassery: Lat: 9.45°, Long:76.55°) . The rain sample fromChanganassery was found to containspores of a lichen-forming alga identifiedas belonging to the genus Trentepohlia.The red colour of the spores was due to thepresence of haematochrome. The othersamples examined also contained similarspores in sufficient quantities to give

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colour to the water. Analysis of samplesfrom the surface at Changanassery showedthat the area was covered with lichens in alarge number. Culture of these samplesshowed that they also belong to the samegenus. It indicated that the spores seen inthe rainwater could be of local origin andwould have come from the surface itself.(part of rainfall studies supported by DST,Govt. of India)

Lightning monitoring

To understand the distribution of lightningincidents over Kerala, a programme tocollect and collate the past data onlightning incidences has been taken up.Data is collected from Revenue records,newspapers and other establishments likeTelecom that are affected by lightning.This data will be used to get a lightningactivity map of the state and also to help inunderstanding the reasons for the activityto happen more frequently in certain areas.Along with the data collection, an electricfield meter is being used to monitoratmospheric electric field. The movementof thunderclouds and their effect onelectric field is being studied with thisdata. The lightning events as recorded bythe meter and the actual area wherelightning struck are being studied toevaluate the usefulness of the electric fielddata.

Facilities Established

An electro-mechanical (Joss-Waldvogeltype) Disdrometer to measure rain dropsize spectrum ( funded by DST). Intensityrain gauges to measure the rainfallintensity are being established at fourdifferent altitudes in the western ghats(funded by DST)

University of Pune, Pune

Measurements of optical properties ofnaturally occurring and anthropogenicaerosols and their distribution are neededto evaluate their climatic impact andmonitor their climatology. Atmosphericaerosols arise from a variety of sources,which include both natural andanthropogenic processes. They play

important role in the radiation balance andenergetics of the earth-atmosphere system.In atmospheric chemistry they provide thebase for heterogeneous chemical reactionssome of which play a vital role in theozone depletion phenomenon in thestratosphere. Aerosols also act ascondensation nuclei in the formation ofclouds. By virtue of these interactionsatmospheric aerosols constitute importantclimate forcing due to their radiative effectand their influence on cloud properties.Optical properties of aerosols depend onthe aerosol size distribution as well as onrefractive index and the shape of theparticles. In order to understand the abovefeatures and their climatic implications onregional and tropical scale, multiplewavelength radiometer (MWR) studies arecontinued from Pune University (18° 32’N, 73° 51’ E, 559 m MSL) under thesponsorship of UGC, CSIR and ISRO-GBP.

Instrument Development

A sun-tracking MWR having wide spectralrange from 380-1020 nm has beenindigenously developed for measurementof direct solar irradiance at the ground.The instrument consists of a sun-trackedplane mirror, which is clock driven. It isdeployed on the open terrace of thelaboratory. The primary mirror reflects theimage of the solar disc on to the entranceaperture of the integrating sphere of theMWR. Homogeneous light beam enteringthe MWR passes through opticalinterference filter and is incident on a solidstate detector whose electrical output isrecorded on a PC with the help of dataacquisition card. The output isproportional to the ground reaching solarflux in the wavelength band of the filter.Eleven narrow band (~10 nm) Opticalfilters covering the above spectral rangeare mounted on a filter wheel that isrotated by a stepper motor to effect achange of filter. From the data, columnartotal optical depth of the atmosphere isdetermined following the Langleytechnique. Columnar aerosol optical depth(AOD) is deduced from the total depth bysubtracting contribution due to Rayleighscattering and ozone absorption.

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The Diurnal Variation of AOD

Two-segment Langley plot is a specialfeature at Pune and it occurs throughout theobservation period from December to May,although it is more prominent during winter(Dec – Feb) when precipitable moistureprovides a strong source of haze particles.

The linear segments, one for the forenoon(FN) and the other for the afternoon (AN),define corresponding AODs. Usually tpl

(FN) > tpl (AN) during winter. This isregarded as the diurnal variation of AOD.Cases of tpl (FN) < tpl (AN) occur on someoccasions during summer.

The difference between tpl(FN) and tpl(AN)is large in December–February and becomesless from March to May. Also the differenceis large in the wavelength range 400-600 nmand is less at higher wavelengths.

The occurrence of tpl(FN) and tpl(AN) isfound to be due to processes in the ABL. Theground gets warmer around the local nooncausing vertical mixing and boundary layergrowth.

About an hour after local noon, convectionbuilds up carrying aerosols vertically upwardsin the cooler environment that is high in RHdue to adiabatic cooling. Aerosol swellingresults causing increase in particle size andabout 30-40% reduction in their extinctionefficiency at shorter wavelengths and hencein their tpl (FN) in the spectral range 380-600nm. The reduced AOD is tpl (AN).Determination of size of aerosols separatelyduring FN and AN shows growth.

In the daily measurements of solar irradiance,the changeover from tpl(FN) to tpl(AN) ismarked by a small enhancement in theintensity of ground reaching direct solar fluxat shorter wavelengths in the spectral range380-600 nm within an hour after the localnoon.

Monthly and Spectral Variation of AOD

AOD is high at 400 nm and low at 800 nm. InApril AOD values range from 0.93 at 400 nm

to 0.70 at 800 nm (summer Maximum) and inDec-Jan from 0.54 at 400 nm to 0.33 at 800nm. (Winter minimum).

Spectral variation has differentcharacteristics during 1998-2001.During19998-99 and 200-2001 the curves displayat least two peaks between 400 and600nm. The data for 1999-2000 show thatAOD is high at 400-500 nm and decreases athigher wavelengths attaining low value at1020 nm. The shape of the monthlyspectral variation is decay type in differentmonths during 1999-2000.

The monthly average aerosol size distributionis mostly decay type during 1999-2000 and isbimodal from December to March and isdecay type in May during 1998-99 and 2000-2001. April appears like a transitional month,with the distribution curve a mixture ofbimodal and decay types.

It is plausible that the source of primary modeaerosols is the atmospheric haze while thesecondary mode particles are ofanthropogenic origin. The latter dominate inApril and May.

Upper air circulation at the top of the ABLexerts strong influence on tpl either throughinflux of marine aerosols and moisture (inFebruary-March) or through theirconfinement (in April), or by controlling thedispersal of aerosols (in May-June).

Angstrom turbidity parameters (a,b) showmonthly variation. a has small positivevalues during December – April showingprevalence of small size particles which isconfirmed by the size distribution analysis.Large size particles prevail in May when ais negative. b is minimum in winter andmaximum in summer.

Results are used for evolving climatology ofaerosol optical depth for the tropical urbanenvironment at Pune.

Indian Institute of TropicalMeteorology, Pune

Atmospheric Electricity

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Data on atmospheric electric field andelectric conductivity obtained at Maitriduring XVI Indian Scientific Expedition toAntarctica showed a peak in electric fieldat 1300 hrs and a secondary peak inelectric field at 1900 hrs. The electricalconductivity did not show any significantvariation during the period ofmeasurement at Maitri, Antarctica. Theresults have been analyzed to study therelative contributions of differentgenerators to the Global Electric Circuit.The atmospheric electric conductivity wasmeasured over the Indian Ocean ondifferent cruises of ORV Sagar Kanyaduring the INDOEX. Results showed anorth-to-south positive gradient ofconductivity extending up to the ITCZ inthe southern hemisphere. Results havebeen used to study the large-scaletransport of aerosols.

Maxwell current density, electric field,precipitation current, space charge densityand conductivity were measured belowthunderclouds. The results showed that therecovery curves of electric field afterpositive lightning were much differentfrom that of the negative lightning whenthe value of pre-discharge electric fieldwas very high.

The vertical profiles of the atmosphericelectrical parameters close to the groundwere computed for different conditions ofthe vertical stability and different values ofthe surface electric field. The effect ofsurface radioactivity was also included.The atmospheric stability of the loweratmosphere was found to have a veryprominent effect on the profiles. Acomprehensive experiment to understandthe atmospheric electrical state ofatmosphere close to the ground wascarried out at the Atmospheric ElectricityObservatory, Pune. Simultaneousmeasurements of different atmosphericparameters viz., atmospheric electric field,conductivity, space charge, air-earthcurrent, ion concentration, atmospherictemperature profile and radioactivity werecarried out.

Five a.c. field mills and five conductivityapparatus were fabricated for the

measurements of electric field andconductivity in the DST project of IndianInstitute of Geomagnetism (IIG) on GlobalElectric Circuit. The instruments werecalibrated, tested and handed over to IIGfor measurements.

Stratosphere-Troposphere EnergyExchange

Association between daily values of zonalwinds in the lower stratosphere and uppertroposphere vis-à-vis solar activity wasinvestigated using the MST Radar specialobservations of winds collected at Gadanki(13.5°N, 79.2°E) during 14 May – 14 June1995. The study suggested that the day-to-day variations in the zonal winds in theupper troposphere or lower stratospherewere not correlated with the sunspotnumber peak values of 10.7 cm solar flux.But zonal winds in the stratosphereshowed good positive correlation withsolar magnetic field variation.

The variations in the total ozone, andcharacteristics of the winds and waveactivity in the region extending from thelower troposphere up to the middleatmosphere during the occurrence of highlatitude stratospheric warmings wereinvestigated by using the data regardingoccurrence of stratospheric warmings inthe high latitudes, rocketsonde wind andtemperature data for the period 1970-1992and the total ozone data for 1°-67°Nlatitude belts for the period 1970-1997.The total ozone was found to be increasedin the high latitudes and decreased in theequatorial regions during the period ofmajor high latitude stratosphericwarmings. Cooling in the tropicalmesospheric and tropospheric regionsfollowed by wind reversal from easterly toweak westerly was also observed.

The daily data of geomagnetic activity(characterized by Ap index) andtemperature and wind (from rocketsondeand radiosonde) at 30 hPa level overVolgograd and Heiss Island duringJanuary-February 1986 were examined tostudy the possible relationship between thegeomagnetic activity, temperature andwind over mid and high latitude stations.

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A statistically significant (< 5% level)negative correlation (r=0.38) betweentemperature and Ap index over Volgograd,while a positive correlation (r=0.37)between zonal winds and Ap index overHeiss Island was revealed. The results canbe explained on the basis of interactionsbetween generation and development ofplanetary wave activity (due to wind andtemperature fields) and geomagneticactivity.

A study of the influence of an Index(geomagnetic activity) on the meanstructures of wind and temperature of thetropical middle atmosphere during thewinter and summer seasons of 1979-1987was carried out by utilising the structure ofthe winds and temperatures derived fromrocketsonde wind and temperature data forThumba (8.5ºN, 76.9ºE) of the Soviet M-100 rockets and aa Index anomaliescalculated from the aa Index 30-year mean(1957-1986). The cold/warm temperaturesat 14 km and associated negative/positiveIndex anomalies during summer werefound to be responsible for the phasereversal of wind from easterly to westerlyin the lower stratospheric levels duringwinter (December).

The association between the space-timeevolution of radar tropopause (sharpenhancement in the radar backscatteredsignal strength) and vertical wind wasinvestigated by conducting specialexperiments at the Indian MST RadarFacility at Gadanki (13.47°N, 79.1°E),Tirupati, Andhra Pradesh over threediurnal cycles on 17-18, 22-23 and 24-25November 1994. The results indicated thatthe atmosphere was more turbulent aroundmidnight, which resulted in the weakeningof the tropopause. The height averagedvertical wind velocity was maximumpreceding and following the occurrence oftropopause weakening. Smaller verticalwind velocity gradients were found to beassociated with the stability conditions inthe tropopause.

A study relating to long-term temperaturetrends in the middle atmosphere vis-à-vispossible global change was undertakenutilizing radiosonde and M-100

rocketsonde data collected over Thumba(8°N) in the 20-80 km altitude region forthe period 1971-1993. An annualnegative temperature trend of 1 - 2.5°K/decade was noticed from 20 to 45 kmand of 2 - 3°K/decade in the lowermesosphere, and a rise in cooling up to5°K/decade in the upper mesosphere. Avariation in trend pattern was observed indifferent seasons. A multiple functionregression analysis of the Rocketsondedata showed a significant solar cyclecomponent in the mesospherictemperature, magnitude of which increaseswith height. A negative correlation in theentire stratosphere and a positivecorrelation in the mesosphere were foundto exist. Solar coefficients fell off withheight above 70 km and the value touchedas high as 4°K/100F at 75 km.

Effect of Stratospheric Changes onClimate

A study of the tropospheric and lowerstratospheric parameters associated withMediterranean cyclones suggested that thecyclonic activity in the Mediterraneanregion could be associated with (i) the lowlatitude surface pressure and (ii) the zonalwinds at 100 hPa level and reversal in themeridional winds in the stratosphericlevels at high latitudes.

From superposed epoch analysis of dailywinds and temperatures during 1971-1987for the summer and winter seasons for thestations Madras, Hyderabad, Kolkata andThiruvananthapuram, increase in windspeed from -3.7 to +3.8 and increase intemperature from 23°C to 28.1°C in thetroposphere following the geomagneticstorms were observed with a lag up to 3days. Also, a 15-day periodicity and a highcorrelation between geomagnetic activityand temperatures/winds over a period of15 days were observed from the spectrala n a l y s i s o f k - i n d i c e s a n dtemperatures/winds (daily values).

A study was carried out to examine therelationship between total ozone andsouthern oscillation index (SOI) duringboth the phases of quasi biennial

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oscillation (QBO) by using total ozonedata for 0° - 20°N latitude and 70° - 100°Elongitude during 1950-1992 for threemonths (June-August) as well as SOI data.It was observed that SOI-ozonerelationship depends on the QBO, i.e.during the periods when the QBO and SOIare in phase decrease in total ozone wasobserved.

The relationship between the frequency ofcyclonic storms, genesis potential (GP)and temperatures in the lower stratosphereat 60°N in the easterly and westerly phasesof QBO for a 36-year period (1964-1998)was investigated. GP values werecalculated by subtracting the values ofrelative vorticity at 850 hPa from those at200 hPa. To calculate GP values,radiosonde data at 00 and 12 GMT wereutilized. GP was found to be greater fordeveloping synoptic scale disturbances inthe westerly phase of QBO than in theeasterly phase of QBO. Also, coldtemperatures in the lower stratosphere at60°N in the westerly phase of QBO werefound to be associated with more numberof cyclonic storms over Indian seas.

Saurashtra University, Rajkot

Monitoring of satellite radio beacon signalstrength fluctuations characterized bysome form of scintillation index providesa simple method to study ionosphericirregularities. The VHF (250 MHz)scintillation observations made at a chainof stations in India under AICPITS wascontinued during the period under report.The data during 19-20 February, 1993,when an extensive “ionization holecampaign” involving other experimentswere also carried out, showed that, onaverage, the scintillation onset was nearlysimultaneous at the equatorial stations upto about 20o magnetic dip angle while asystematic time shift that progressivelyincreased with dip angle was observed.The vertical rise velocity of the plasmadepletions estimated from the time delayswas found to range from 40m/s to 420 m/sin the altitude range 300 to 1350 km.

Applying power spectral analysis to thedigital scintillation data recorded at Rajkotfor an extended period , 1991 to 1993 ,quantitative parameters such as S4 index,fade rate, upper roll off frequency, spectralslope etc are derived and discussed interms of the parameters of the causativeplasma irregularities. The effect of theirregularities on communication systemsin terms of signal statistics such ascumulative amplitude distributionfunctions, fade rate, message reliabilityand bit error on a typical communicationsystem are computed.

The association between the equatorialelectrojet strength and ionosphericscintillation at the anomaly crest station,Rajkot is investigated. The EEj strength islow on days of weak premidnightscintillations and high on days of strongpremidnight scintillations. This in turn isconsistent with a good correlation betweenthe post sunset enhancement in F regionvertical drift and EEJ. Thus a positivecorrelation between daytime E-regiondynamo and nighttime f region dynamocan be inferred.

Nocturnal, seasonal and solar activityvariations of VHF scintillation occurrenceat the equatorial and anomaly crestlocations in India are presented andcompared with corresponding variations inspread F occurrence. At equator,scintillation and range spread F occurpredominantly in the pre midnight periodof equinoxes and increase with solaractivity. At anomaly crest, scintillationoccurrence is always less than at equatorwith similar patterns in equinoxes. Postmidnight scintillations are generallyassociated with frequency spread F,predominant in summer and decreaseswith solar activity. Comparison of spreadF occurrence in Indian and Brazilianequatorial locations brings out themagnetic declination control.

These scintillation characteristics aremodeled empirically using the cubic-spline technique and good agreementbetween the observed and modeled valuesof scintillation occurrence percentage and

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their latitudinal and local time pattern isobtained.

Multitechnique investigations of ESFphenomena using GPS spaced receiverscintillations, ionosonde spread F, VHFradar and air glow photometer over theequatorial and low latitudes in Brazil arecarried out to bring out interesting featuresof the equatorial ionospheric plasmabubble phenomenon and its dynamics.

Studies using the Interplanetaryscintillation array at Rajkot.

Using the interplanetary scintillation (IPS)observation at 103 Mhz at Rajkot , solarwind velocity estimate using IPStechnique at 327 MHz at Nagoya, Japan,ionosonde observations at Ahmedabad,enhanced interplanetary scintillation index(plasma turbulence) and a reduced solarwind velocity during the passage of theinterplanetary disturbance consequent to asolar flare on 12 May,1997 were observed. The D-region ionization increase due tothe x-rays emitted during the flare wasinferred from the ionosonde data.

Using a novel radio astronomicaltechnique, the presence of TravelingIonospheric Disturbances (TID) aredetected from observations of radiostarsignals by the IPS system at Rajkot for thefirst time. To study the ionospheric TIDs,signals from different radio stars arerecorded daily using the radio telescope.When TID is present, the radio wavepasses through undulated ionospherecausing ray deviation by refraction leadingapparent position shift of the source andcorresponding intensity variation at thereceiver. The measurements at tworeceivers looking at two different sourceswhose ionospheric crossover points arespaced horizontally, show consistent timeshift of similar features due to the passageof TID across the line of sight. From thetime shift and estimating the horizontaldistance between the ionospheric crossover points, the speed of the TID isestimated. Observed TID periods are 20-24 minutes and the north –southcomponent of their speed ranges from 66-273 m/s. This is characteristic of medium

scale TID originating from atmosphericgravity waves.

MST radar studies of atmosphericdynamics in the tropical atmosphere

Study of dynamical phenomena such astides and waves and their role in couplingbetween the different regions in the middleatmosphere have been continued. Seasonaldifferences of diurnal tidal oscillations inzonal and meridional winds using IndianMST radar located at Gadanki (13.5o N,79.2oE) have been brought out. Diurnaltidal amplitudes vary from 2-3 m/s atlower heights to 8-10 m/s at higherheights. The vertical wavelength alsovaries from 3-4 km in the lowertroposphere to 5-7 km in the uppertroposphere. The observed amplitudes andphases in different seasons are consistentwith numerical simulations of non-migrating tides. These tides withamplitude ~10m/s observed in the monthof august over Gadanki may be associatedwith latent heat released by deepconvective activity in this thunderstormseason.

Our earlier studies had identified thepresence of Kelvin waves with period ~12-14 days and mixed Rossby gravity waveswith period of ~4-5 days in this tropicalmiddle atmosphere. The momentum fluxcarried upward by these waves have beenestimated now and found to be significantto contribute to the mean flow changes.The presence of gravity waves of periods15-35 minutes and their propagationcharacteristics have been inferred fromboth MST radar and LIDAR observationsfrom the same location.

Physical Research Laboratory,Ahmedabad Space weather studiesUsing IPS observations of 103 MHz madeat Rajkot, a few events were investigatedwith a view to understand the solarterrestrial relationship, these are Earthdirected CMEs and the so called solarwind disappearance event. For theinvestigation we also used the satellitedata (ACE) of solar plasma parametersand find a good corresponds in the in-situ

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and the IPS measurements. It is seen thatproperly oriented relatively weak CMEevent could cause a reasonable effect onthe terrestrial environment. One of themost Geoeffective coronal mass ejection(CME) has been that of April 4, 2000. Asseen in SOHO/LASCO images a haloCME with a bright front began on April04, 2000 at about 1632 UT. This appearedto be associated with C9 flare in AR 8933.With IPS observations at 103 MHz, wedetected the effect of this CME at the lineof sight of 3C459 two days later and atthe line of sight of 3C2, 3C119 and3C122 three days later. At the line of sightof 3C48 there appeared a very feeble or noeffect of the passage of this CME. Thiscould be due to the projection effect of theCME or along that direction theinterplanetary disturbance associated withthe CME is absent. The CME of April 4,2000 produced a shock which wasdetected by ACE solar wind velocitymeasurement (the radial velocity increasedfrom 375 km s-1 to 575 km s-1 at 16 UT onApril 6, 2000). This shock led to a verylarge drop (~ 300 NT) in equatorial Dstand produced one of the largestgeomagnetic storm of this century. ThisCME appears to be very geoeffectivewhere as there are several others not soeffective in producing disturbances in theterrestrial environment. In fact this poses aserious problem for the prediction ofgeomagnetic storms and substorms. Thiswork is done in collaboration with SURajkot. Study of solar rotation

Investigations of the solar coronal rotationusing radio emissions probes were made.It was possible to find unique features oneof these has been the discovery ofdifferential rotation as a function of heightin the solar corona. Recently this methodwas extended to chromospheric emissionLyman Alpha whose measurements areavailable over many years 1947 – 1999.The auto and cross correlation analysis isused for this. We found that the rotationalmodulation is highly variable. In severalyears it is very high up to 60% and insome others the evidence of rotationalmodulation is negligible. The rotational

modulation shows evidence of longerperiod (> 100 years) in Lyman Alphawhich is not so evident from sunspotnumbers. The cross correlation coefficientof the sunspot number and solar Lyman airradiance has a peak positive value of0.12 at a lag of 5 years and a peak negativevalue of -0.18 at a lag of -1 year. Thusrotational modulation is highly variableand seems to be almost independent of thephase solar activity cycle. The synodicrotation period is also found to be variablewith maximum as much as ~ 32 days. Therotational modulation appears to be verydifferent during the year 1979. Thispeculiarity is differently present in boththe Lyman Alpha emissions as wellsunspot number. The modulation index isreasonably large in both, but the period isridiculously small. The cross correlation ofLyman Alpha and sunspot number isalmost zero.

Ionospheric studies Ionospheric data over Ahmedabad for1955-1996 were examined for long-termchanges due to the cooling of themesosphere and thermosphere byincreased green house gases. F layer peakdecreases by about 10 km in 40 years. Thecritical frequency of the F2 layer decreasesby 1 MHz in this period but of the F1

layer increases by 0.3 MHz. The resultsare consistent with the predictions ofRishbeth and Roble.

Enhanced sporadic-E occurrenceassociated with Leonid meteor showersstarting from 1996 and peaking in 1998was noticed from ionosonde data. Multipletraces between 100 and 150 km appear onsome occasions for both the years 1998and 1999, which lend support to theassociation of meteor shower with thesporadic-E observed.

VHF scintillations at 244 MHz at Calcuttaduring the night of 16-17 November 1998are shown to be associated with thesporadic-E layer generated by meteoricionization. Two examples of scintillationscorresponding to the peak period ofLeonid meteor shower are transient andquasi-periodic in nature with much shorter

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duration (30-100S) than normallyobserved. Critical frequency of thesporadic-E layer over Ahmedabad alsoshows two isolated spikes. Observationsare validated using the diffraction theoryfrom a series of one-dimensionalirregularities

VHF (244 MHz) scintillations at a chain of20 stations in India during AICPITScampaign (February-March 1993), wereused to estimate the vertical velocity oflarge-scale plasma depletions associatedwith equatorial spread-F from the meantime delays between the onset times ofscintillations. The velocities of 40-420 m/swith maximum at altitudes of 400 to 800km are consistent with the in-situ electricfield measurements from satellites.

Simultaneous in-situ measurements of thefluctuations in electron density and electricfield during strong spread-F were made forthe first time in India. Strong irregularitieswere seen at 160-190, 210-257 and 290-330 km regions. Intermediate scalevertical electric field fluctuations showedspectral index of –2.1 below the F-layerbase as compared to –3.6 in the valleyregion and –2.8 below the F-layer peak.

Detailed analysis of 630 nm and 777.4 nmimages from SHAR showed that on highlydisturbed magnetic epochs, the inter-depletion distance increased by a factor ofabout 2 and became as high as 1600 km.This is the first experimental evidence thatthe gravity waves of auroral origin areresponsible for modulation of the bottomside of the F region. During magneticallyquiet periods, gravity wave with origin inthe lower atmosphere were responsible forperturbing the F region

Two rocket-borne experiments wereconducted from SHAR, on 18 and 20November, 1999 during morning hours toinvestigate the effects of Leonid meteorstorm. The ion composition measurementsreveal presence of ions in the range of 55to 60amu presumably Fe+ ions associatedwith Leonid storm. Electron density datado not show any thin layer of orirregularities in scale size of 100 m downto 3 m. The result reveals the significance

of electrodynamical processes at 6o awayfrom dip equator.

A coordinated campaign was conducedduring March, 1998 and 1999 to studyequatorial F region irregularities. TheMST radar was operated in ionosphericmode for mapping structure (RTI maps)and dynamics of the F regionirregularities. 630 nm night airglowintensities using a photometer in a bi-directional scanning (zonal) modeprovided zonal drifts from identifiablefeatures. Similar patterns were seen in theairglow intensities and MST radar maps.Downward moving structure recorded inMST radar was identified to be anenhancement in 630 nm intensitiescorresponding to the enhancements in theambient ionization. The high altitudeenhancements in electron densities duringESF are shown to be due to the interactionof two long wavelength modes as a seedperturbation in the non-linear evolution ofESF.

Electric field perturbations with scale sizessimilar to those of the gravity waves arerequired to initiate large-scale structures inthe ESF. It is shown that when the E layeris thin, the perturbation electric fieldsproduced through Hall conductivity aremuch larger than those produced throughthe Pedersen conductivity. Theperturbation electric fields producedthrough Hall conductivity transmitted tothe F region via the geomagnetic fieldlines were shown to be more suitable fortriggering of the ESF than those producedthrough Pedersen conductivity.

From rocket-borne measurements ofionospheric current and groundgeomagnetic data in the equatorial region,linear relation are found between the peakcurrent density and range in H for Indianand American longitude sectors to convertthe long series of geomagnetic data intopeak current density. Electron driftvelocity is estimated using E-region peakelectron density. Ionospheric currents andelectron drift velocity, show strongequinoctial maxima. The solar cyclevariation of electrojet is primarily due toelectron density while seasonal variations

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are due to electric field. The currents arestronger in the American sector (24 %)caused primarily by the larger electrondrift velocity (33 %).

2 RH 300 Mark II rockets were launchedon 18th, 20th November 1999 from SHAR,during Leonid shower activity. Highfrequency Langmuir probe reveals anexperimental evidence for the first time forthe presence of sub-meter scale sizeplasma waves during Leonid meteor stormwith maximum amplitude of these about4% of ambient at 105 km on both the days.Evidences are obtained that the causativemechanisms for the generation of theplasma waves are different from gradientdrift and two stream plasma waves. Theassociation of the sub-meter waves withthe activity of Leonid meteor storm is alsoobtained

Evolution of equatorial spread F structureswith perturbation consisting of a singlewavelength mode and superposition of twomodes was studied. Depleted regionalways moves up with a single wavelengthmode while the superposition of twomodes gives rise to low level plasmadepletion which moves downward evenwhen the ambient plasma motion isupward, in addition to well developedupward moving plasma bubbles and downdrafting enhancements. Well-developedplasma bubbles with scale sizecorresponding to smaller wavelengthmode is possible even with very small(0.5%) perturbation when it rides over along wavelength mode with largeperturbation (5%). The longer wavelengthmode develops to form a lower envelopover which multiple plumes with varyingdegree of depletions ride over, plumesseparation decided by the shortwavelength. The rising multiple plumesand the descending structure along withdownward moving streak observed by theMST radar is explained.

Satellite observations of ESF revealed thepresence of molecular ions (NO+) in thetopside ionosphere and enhancementswere collocated with the depletions inatomic oxygen (O+). To understand thepresence of short-lived molecular ions at

higher altitude, two fluid model is used toinvestigate the nonlinear effects ofmolecular ions. It is shown that theplasma transport processes associated withthe plasma instability bring the plasmafrom the base of F-region. Depletion inO+ is collocated with the enhancement inmolecular ions similar to satelliteobservations. The variations in NO+ athigher altitudes are associated with thevariations of the relative concentration ofNO+ and O+ at the base of the F-region.

The rotational temperatures in the daytimemesopause region obtained by the multi-wavelength dayglow photometerobservations at Tirunelveli showed diurnaland day to day variabilities. Derivedtemperatures were significantly differentfrom the MSIS-90 model temperatures.

DE-2 satellite data were examined tounderstand the Equatorial temperature andwind anomaly (ETWA) and a plausibleexplanation was given on the basis ofchemical heating due to exothermicreactions and the frictional heating due toion-drag. Temporal variation in theintegrated E-region conductivity and itssubsequent loading effect on F-regiondynamics over low latitudes during daywas considered to account for the iondragassociated heating at all local times.

Studies on Dusty Plasma

New results have come out of the work ondusty plasmas. The concept of the dustfugacity has been introduced and dustyplasmas have been classified into tenuos,dilute or dense types. A new kind of dustwave mode driven by Coulumb pressurehas been found in dense regime. Thismode can be considered as thee lec t ros ta t ic ana logue of thehydromagnetic (Alfven) waves in ordinaryplasmas. Dust plasmas are shown to begoverned by a new kind of length scale,which plays a fundamental role in thedense regime, like the Debye length of thetenuos regime.

Indian Institute of Technology,Kharagpur

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200km long magnetotelluric traverse wascompleted from Khorda to Keonjhar inOrissa during this period which cuts acrossMahanadi graben, major faults near riverBrahmani, Sukinda thrust(an Archaean-Proterozoic contact between the northernmargin of the high grade granulitic terrainand the Singhbhum craton) andSinghbhum granite batholith(SBG-A)It isa part of the work under Chilka –Gangtokgeotraverse program of DST.

100km long magnetotelluric traverse wascompleted from Khandwa to Barwaha inMadhya Pradesh during this period whichcuts across the Khandwa Lineament andNarmada –Son Lineament. Thisprogramme was sponsored by GeologicalSurvey of India.

Salient features of results

Lower crust is highly conducting andremarkably horizontal below Eastern GhatMobile Belt(EGMB) from Khorda to thenorthern margin of the Eastern Ghat.Higher conductivity from MT and higherductility from DSS (Kaila, NGRI, 1985)matched. Presence of plenty of biotites,graphites, banded iron formations(BIFs)and magnetite quartzites in Khondalitesare responsible for higher conductivitywhen they got mixed with the percolatedmeteoric water through the major faultsand graben type structures near riverMahanadi and Brahmani. Higherconductivity of the lower crust made thedetection of Moho possible here. Becausethe olivine dominated ultrabasics in theupper mantle is less conductive than lowercrustal conductive mixture at Mohotemperature. Model experiment hasshown that the probability of detection ofMoho increases when the structure isnearly 1D.Estimated depth of the Moho is38km from MT and 34 km from DSS.

The property ‘Static Shift’ can bequalitatively used for detection of faults/fractures/sutures/lineaments. Bothamplitude and phase of the horizontalcomponents of the magnetic field showsharp changes across a fault. Thereforemajor faults can be detected by examining

the horizontal components of the magneticfields.

In general the thickness of the lithospherealong the Chilka-Gangtok geotraversevaried from 90 to 120 km. This estimateroughly matched with the estimate oflithospheric thickness of the northern Indiagiven by IIG, Mumbai.

Rotation invariant apparent resistivitiesand phases, viz. (rho_determinant andphi_determinant),( r h o _ a v e r a g e , p h i _ a v e r a g e ) a n d(rho_central,phi_central) generate muchmore closer and more consistent earthmodels than those generated by(rho_TE,phi_TE) and (rho_TM,phi_TM).Plots of rotation invariant apparentresistivities and phases are more stablewith smaller error bars.

TE and TM mode models are never samefor real field conditions. Therefore to trusta geoelectrical model inversion should bedone with different MT parameters anddifferent inversion softwares. And thecommon features of all the models shouldbe taken with greater confidence levelalthough the geometrical shapes of theCommon features may be different.

Mathematical modeling revealed that TMmode MT resolves the subsurface withgreater clarity than that done by TE modeMT specially to resolve vertical contacts.For lithospheric studies, it is alwaysadvisable to search for granite windows orhard rock areas for field observation.

Repeatable observation should be givengreater weightage. Since data weightagevaries inversely with error bar, uncertaintylevel in the parameter estimation increaseswith error bar.

Survey of India, Dehradun

Surface data acquisition and analysisduring the period under report:Observations of Declination, Horizontalforce and Vertical force and 138 repeatstations, 104 profile stations and 15 fieldstations were carried out in various partsof the country for preparation of

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Isomagnetic charts for Declinations,Horizontal Force and Vertical Force forepoch 2000.0 chart of MagneticDeclination of epoch 2000.0 is in finalstage The 104 Nos. of Profile stationswere observed in connection withseismotectonic studies.

Madras Institute of Magnetobiology,Chennai

The Institute founded in 1984 as aregistered non-profit scientific Society ofTamil Nadu, has been engaged infundamental and applied research anddevelopment of Pulsed Magnetic Field(PMF) technology. Given below is anoutline of the R&D activities engaged inby the Institute during the period Jan 1998to Dec 2002.

Clinical applications of PMF for thecure/palliation of a variety of humanailments/functional disorders such asarthritis (rheumatoid and osteo),spondylosis, non-uniting fractures,festering wounds of various aetiologieslike post-surgical non-healing wounds,diabetic ulcers, burns etc, spasticity inchildren and epilepsy.

The Institute has a separate therapy andclinical division where PMF treatment isbeing offered to out patients with theseailments. During the reporting period atotal number of 850 cases have beenhandled by the division. The division alsohas ongoing projects in collaboration withother Institutes.

Based on a few earlier pilot studies, anexperiment was carried out incollaboration with the Central SericultureResearch and Training Institute (CSRTI),Mysore on application of PMF to silkworm eggs. The results showed a strongenhancing effect of PMF on the cocoonweight and tensile strength of the silkfilament besides also showing a decreasein the mortality of the worms.

A series of pilot studies were carried out (as an intramural effort) on the possiblecontrol of PMF in the biodegradation ofeffluents from sugar distilleries and

tanneries. The efficacy of bacterial cellsexposed to PMF in treatment of theeffluent was compared with that ofunexposed cells.

The first results of these pilot experimentshave been highly promising and awaitfurther detailing as to the specificfrequency-intensi ty-dose durat ioncombinations of PMF which would showthe most optimal performance in thebiodegradation.

Instrumentation

The Institute has been from the beginningsupported by an Instrumentation groupsince none of the CMF enclosures for thespecialized studies, can be procured fromany market and also the calibrationprocedures are not conventionally known/practised.

All the CMF coil enclosures likeFransleau-Braunbeck type, Reuben cubiclattice system, Helmholtz coils andsolenoid enclosures were all designed,fabricated, erected and calibrated by theMagnetic Standardization Lab of theInstitute. Foir calibration a "La CourDeclinometer" assembled to operate as anull field system and also the AskanianField Balance and the Danish ZeroBalance Magnetometer (BMZ) are beingused.

Barkatullah University, Bhopal

At Space Science Laboratory, BarkatullahUniversity, Bhopal, the emphasis hasbeen to understand the dynamics ofionosphere and magnetosphere via radiobeacon experiments and VLF waveobservations. Study of the ionosphericscintillation is being carried out fromVHF-receiver system. This system ismonitoring Radio Beacon Signal at 250MHz from FLEETSAT Satellite situated atequator around 73 degree East longitude.Analysis of the data will givemorphological details of ionosphere at lowlatitude (Bhopal).

TEC measurement are being done throughFaraday rotation method and data are

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being taken from different satellites byIndian Space Research Organization, Indiaand World Data Center, USA. . The groupis collaborating Trieste, Italy with Prof.S.M.Radicella on the problems ofionospheric modeling and its variability atlow, mid and high latitudes.

The GPS satellite navigation system isaffected in two ways, namely, IonosphericDelay Errors (proportional to TotalElectron Content) and Scintillations. Tostudy above two effects we use GPS datafor detecting ionospheric irregularities,which affect the navigation andcommunication. Rapid phase andamplitude variations on the GPS signalscausing GPS receiver to loose lock. Theeffect of Seismo electromagnetic signalrelated to the ionospheric perturbationsduring Earthquake with the help of GPSreceiver are also being investigated..

The study of Whistler at Bhopal, a lowlatitude station and at Antarctic, a highlatitude station are being carried out.Using an improved antenna and VLF-receiver system. Analysis of VLF- signalreveals the occurrence of Whistler, whichare useful in the diagnostics of Ionosphericparameter such as : density, temperature,etc. Modified version of VLF receivingsystem along with digital tape recorderinterface with Computer is being used forVLF analysis.

The detail linear and non-linear analysis ofelectromagnetic and electrostatic cyclotroninstabilities has been taken up. Thestability criteria for various wave modessuch as electron cyclotron (Whistler), Ioncyclotron, magnetospheric, etc. have beenstudied. Application of these studies areincorporated in explaining satellite data forplasma Waves and Electric fields fromISSE 1 and 2. The existence of electricfields and electric currents (field alignedcurrents) have significantly changed thee l e c t r o d y n a m i c s , e n e r g i z a t i o n ,precipitation and acceleration of chargedparticles in the magnetosphere. A detailedtheoretical study is being undertaken tounderstand the structure of field andcurrent in the magnetospheric region,microscopically. The effect of electric

field on the wave generation inmagnetospheric is being categoricallystudied.

Publications

Abdul Hameed M.J., M.Vivekanandan,T.Leelapriya, P.V.Sanker, Narayan,(1999). A new technique of pulsedmagnetic field for growth and yield ofSorghum vulgare, Proceedings ofInternational conference on " LifeSciences in the next millennium",H y d e r a b a d , D e c 1 1 - 1 4 .

Agashe V V, (2000). Atmosphericaerosols and their role in radiative transfer,in Cloud Physics and AtmosphericElectricity Fundamentals, Volume I,edited by K. Kamra and P. PradeepKumar, Lecture notes of First SERCschool, IITM, Pune, pp. 207-228.

Aher G.R, N. Shantikumar Singh, V.V.Agashe, (2002) Study of AtmosphericTransparency over Pune,.In Proceedingsof TROPMET 2001 (NationalSymposium on Meteorology forsustainable Development), Published byIndian Meteorological Society ( AlliedPublishers Pvt Ltd, Mumbai) pp 485-591.

Aher G.R., and Agashe V.V,(2001).Influence of Climatic Factors onAerosol Optical Depth, J. of Marine andAtmos. Res.,Vol. 2 (No. 1), pp. 46-50.

Aher G R and Agashe V V, (2000).Aerosol properties over tropical urbanenvironment at Pune, in IGBP in India2000, INSA, New Delhi, pp. 184-205.

Aher G R, N. Shantikumar Singh andAgashe V V, (2000), Features of AOD at aTropical Urban Environment at Pune, inNucleation and Atmospheric Aerosols,edited by B. N. Hale and M. Kulmala,Amer. Inst. Phys. Conf. Proc., 534, pp.593 – 596,

Aher G R, Sen P N and Agashe V V,Effect of boundary layer circulation onaerosol characteristics, in Long TermChanges and Trends in the Atmosphere,

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Vol I, edited by G. Beg, New AgePublishers, New Delhi, pp. 280-292.

Aher G.R., N. Shantikumar Singh and V.V. Agashe, (2000). Features of AOD at aTropical Urban Environment at Pune, inNucleation and Atmospheric Aerosols2000, Proc. 15th International Conference,Editors Barbara N. Hale and MarkkuKulmala, Rolla, Missouri, Published byAmer. Inst. Phys. New York, pp. 593 –596, Aug. 2000.

Aher G.R. and V V Agashe, (2000).Aerosol properties over tropical urbanenvironment at Pune, in IGBP in India2000- A Status Report on Projects, Ed. R.Narasimha, I.P. Abrol, George Joseph, SW A Naqvi, D. C. Parasher, P. B. Rao andB. H. Subbaraya, INSA publication, NewDelhi, pp. 184-204, 2000.

Alex S., S. Mukherjee, L. Jadhav andD.R.K. Rao, (2000). Equatorial electrojectcharacteristics: and its longitudinaldependence, The Journal of IndianGeophysical Union, 4, 57-63.

Alex S. and S. Mukherjee, (2001). Localtime dependence of equatorial electrojectcounter electroject effect in a narrowlongitudinal belt, Earth Planet & Space,53, 1151-1161.

Arun T, A.G. Patil, Ajay Dhar and GirijaRajaram.,(2000). Rapid decrease in totalmagnetic field intensity at Indian AntarcticStation Maitri, J. Ind. Geophys. Union, 4,No. 2, pp. 119-128.

Anand S.P. and Mita Rajaram,(2002). Aeromagnetic data to probe theDharwar craton, Current Science 83, No.2,July 25, 162.

Anand S.P., V.C. Erram and MitaRajaram, (2002). Crustal structuredelineation of Mahanadi basin fromground magnetic survey, J. Geol. Soc.India, 60, 283.

Arora B.R., Gautam Rawat and AK Singh,(2002). Mid crustal conductor below theKutch rift basin and its seismogenic

relevance to the 2001 Bhuj earthquake,DCS Newsletter, 12(2).

Arora B.R. and P.B.V. Subba Rao,(2002). Integrated Modeling of EMResponse Functions From Peninsular Indiaand Bay of Bengal, Earth Planet Space,Japan, 54, 637-654.

Arora B.R. (2002). Seismotectonics of theFrontal Himalaya through the ElectricalConductivity Imaging In: Seismotectonicsin Convergent Plate Boundary, Eds: Y.Fujinawa and A Yoshida, Terra Pub.,Yokyo, 261-272.

Arora B.R. et al., (2001). GeophysicalInvestigations in the January 26, 2001Bhuj Earthquake Affected Region, Proc.Workshop on Recent Earthquakes ofChamoli and Bhuj, Dept EarthquakeEngg., Univ Roorkee, Vol. 2, 503-514.

Arora B.R. , P.B.V. Subba Rao, Nalin B.Trivedi, Antanio L. Padilha and IcaroVetorello,(2001). Appraisal ofelectromagnetic induction effects ongeomagnetic pulsation studies. Annales.Geophysics 19, 171-178.

Arora B.R., & C.D. Reddy, (2001).Correlation between High ElectricalConductivity and Seismicity : Role ofFluids In: Research Highlights in EarthSystem Science, Focus on Seismicity, Ed.O.P. Verma, DST, V. 2, Ind. Geol. Cong.,Roorkee, 2001, 267-276.

Arora B.R., (2000). Effects of anomalouselectromagnetic induction in the source-characterization of equatorial geomagneticfluctuations, J. Ind. Geophys. Union.Special Issue (Equatorial Geomagnetism)4, No.2(a), 29-39.

Arora B.R., (2000). Geomagnetic DeepSounding Studies in India : TectonicImplications, In: Research Highlights inEarth System Science, Focus on deepContinental Studies, Eds. O.P. Verma andT.M. Mahadevan, Indian GeologicalCongress, V 1, 113-122.

Arora B.R., (2000). Upper MantleElectrical Conductivity Distribution

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Beneath the Indian Sub-continent In:Research Highlights in Earth SystemScience, Focus on deep continentalStudies Eds. O.P. Verma and T.M.Mahadevan, Indian Geological Congress,V 1, 143-150.

Arora B.R., (1999). Seismotectonics of theFrontal Himalay through the ElectricalConductivity Imaging Proc. InternationalWorkshop on Seismotectonics at theSubduction zone, Tsukuba, Nov.29-Dec.1,Vol.1, 275-286.

Arora B.R., N.B. Trivedi, I. Vitorello,A.L. Padilha, A. Rigoti and F.H.Chamalaun, Braz. (1999). Geomagneticdepth sounding as applied to the ParnaibaBasin, J. Geophys. 17, 43-65.

Arora B.R. , A.L. Padilha, I. Vitorello,N.B. Trivedi, S. Fontes, A. Rigoti and F.H.Chamalaun, (1999). 2-D geoelectricalmodel for the Parnaiba basin conductivityanomaly, north-northeast Brazil and itstectonic implications, Tectonophysics,302,57-69.

Arora B.R., K.V.V. satyanarayana andA.S. Janardhan, (2002). MagneticMineralogy and Palaeomagnetism of theOddanchatram Anorthosite, Tamil Nadu,DCS Newsletter, 12, No 1, 6-9.

Banola, S., B.M. Pathan and D.R.K. Rao,(2001). Strength of the equatorialelectrojet and geomagnetic activity controlon VHF Scintillation at the Indianlongitudinal zone, Ind. J. Radio & SpacePhys., 30, p. 163-171.

Bharuthram, R., R. V. Reddy, G. S.Lakhina and N. Singh, (2002), Low-frequency nonlinear waves in the auroralplasma, Physica Scripta, T98, 137-140.

Bhattacharyya, A., (1999). Deterministicretrieval of ionospheric phase screen fromamplitude scintillations. Radio Science,34, 229 – 240.Bhattacharyya, A., T. l. Beach, S. Basuand P. M. Kintner, (2000). Nighttimeequatorial ionosphere: GPS scintillationsand differential carrier phase fluctuations,Radio Sci., 35, 209 – 224.

Bhattacharyya, A. and W. J. Burke,(2000). A transmission line analogy for thedevelopment of equatorial ionosphericbubbles, J. Geophys. Res., 105, 24941-24950.

Bhattacharyya, A., (2001). Irregularities inthe nighttime equatorial ionosphere and L-band scintillations, Proceedings of theInternational Beacon Satellite Symposium,ed. P. H. Doherty, pp. 2-6.

Bhattacharyya, A., S. Basu, K.M. Groves,C.E. Valladares, and R. Sheehan, (2001).Dynamics of equatorial F regionirregularities from spaced receiverscintillation observations, Geophys. Res.Lett., 28, 119-122.

Bhattacharyya et al.,(2002). J. Geophys.Res. 107, 1489.

Bhuyan P.K, Chamua M., SubrahmanyamP. and Garg S.C., Diurnal, (2002).Seasonal and latitudinal Variation ofElectron Temperature Measured by theSROSS-C2 satellite at 500 km altitude andComparison with IRI, AnnalesGeophysicae 20, 807-815.

Bhuyan P.K., Kakoty P.K., Garg S.C. andSubrahmanyam P. , (2002). Electron andIon Temperature and Electron Density at ±100 Magnetic Latitudes from SROSS-C2measurements over India and Comparisonwith the IRI. Adv. Space Res., 29, 865-870.

Buti B., V. l. Galinsky, V I. Shevchenko,G. S. lakhina, B. T. Tsurutani, B. E.Goldstein, P. Diamond and M. V.Medvedev, (1999). Evolution of non-linear Alfven waves in streaminginhomogeneous plasma, Astrophys. J.,523, 849-854.

Chakrabarti, N. and G.S. Lakhina, (2001).Nonlinear saturation of Rayleigh-Taylorinstability and generation of shear-flow inequatorial spread-F plasma, Nonl. Proc.Geophys., 8, 181-190.

Chandra H, Jayaraman A, Ramaswamy Sand Acharya Y B, (1999) Temperature

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structure and dynamics studies byRayleigh Lidar , In ‘AdvancedTechnologies in Meteorology’, TataMcGraw-Hill Pub. Co. Ltd., edited by R KGupta and S Jeevananda Reddy.

Chandra H, Sinha H S S and Rastogi R G,Co-ordinated study of EquatorialElectrojet Current from Rocket andGround Data , J. Ind. Geophys. Union, 4,P 23-28, 2000.

Chandra H, Som Sharma, Devasia C V,Subbarao K S V, Sridharan R, Sastri J andRao V S , Sporadic-E associated withLeonid meteor shower event of November1998, over low and equatorial latitudes,Ann Geophysicae, Vol. 19, P 59-69, 2001.

Chandra H, Rastogi R G and Sinha H S S,Equatorial electrojet studies from rocketand ground measurements, Earth Planetsand Space, 52, 111-120, 2000.

Chandra H and Sharma S, (2001).Longterm changes in the ionosphere, in Longterm changes and trends in theatmosphere, Volume II, ed. By GufranBeig, New Age International (P)Ltd., pp 109-126.

Choudhary R.K. and Mahajan K.K.,Tropical E, (1999). region field alignedirregularities: Simultaneous observationsof continuous and quasi-periodic echoes.,J. Geophys. Res., 104, 2613.

Dabas R.S., Lakshmi D.R. and ReddyB.M. , (1998). Day to day variability in theoccurrence of equatorial and low latitudescintillations in the Indian zone., RadioSci., 33, 89-96.

Dabas R.S., Reddy, B.M., Lakshmi D.R.and Oyama K.I. , (2000). Study ofanomalous electron temperature variationin the topside ionosphere HINTORIsatellite data., J. Atmos. Solar & Terr.Phys., 62, 1351-1339.

Das, A.C. and Ip, W.H., “field AlignedCurrent and Particle Acceleration in thenear-lo Plasma Torus”, Planet. Space Sci.,48, 127-131, 2000.

Deshpande C.G. and Kamra A.K., (2001).Diurnal variations of the atmosphericelectric field and conductivity at Maitri,Antarctica, Journal of GeophysicalResearch, 106, 14207-14218.Dhanorkar S.S. and Kamra A.K., (2001).Effect of coagulation on the particlecharge distribution and air conductivity,Journal of Geophysical Research, 106,12055-12065.

Dhar, Ajay, AL Gudade, S Sankaran andGirija Rajaram, (2000). Studies of localtime characteristics in Magnetometer andRiometer variations at the Indian AntarcticStation, Maitri, Technical Publication No.14, Scientific Report of SixteenthExpedition to Antarctica, DOD, 75-92.

Dhar A., S. Sankaran and Girija Rajaram,(2000). Three stations magnetometerexperiment at Antarctica during Jan 1996,to determine the velocities of disturbedtime overhead auroral current systemsScientific Report of 15th Indian AntarcticExpedition to Antarctica, Tech. Pub.No.13, 1-20, DOD.

Elango P., A. L. Gudade, S.Sankaran,Ajay Dhar and Girija Rajaram, (2000).Velocity of small-scale current systemover Maitri, Antarctica in Jan. 1997.Tech. Pub. No.14, Scientific Report ofSixteenth Expedition to Antarctica, DOD,75-92.

Federov, E.,V.Pilipenko,V.Surkov,D.R.K.Rao and K.Yumoto (1999).I o n o s p h e r i c p r o p a g a t i o n o fmagnetohydrodynamic disturbances fromthe equatorial electro- jet, J. Geophys. Res.104, 4329-4336.

Garg S.C., Anand J.R., Bahl M.,Subrahmanyam P., Rajput S.S., MainiH.K., Chopra P., John T., John S.K.,Vishram Singh, Dhan Singh, Das U.N.,Bedekar S.M., Soma P., Venkateswarluand Goel D.P., (2003). RPA aeronomyexperiment onboard the Indian satelliteSROSS-C2 – Some important aspects ofthe payload and satellite Indian journal ofRadio & Space Physics, 32.

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Ghosh, S. S., A. Sen and G. S. Lakhina,(2000). Dromion solutions for an electronacoustic wave and its application to spaceobservations, PRAMANA – J. Phys., 55,693-698.

Gulyaeva T.L. and Mahajan K.K. ,(2001). Dynamic boundaries of theionosphere variability., Adv. Space Res.,27, 91-94.

Gupta J.K. and Singh L. , (2001). Longterm ionospheric electron content overDelhi., Ann. Geophys., 18, 1635-1644.Gupta J.K., Singh Lakha and Dabas R.S.,(2002). Faraday polarization fluctuationsand their dependence on post sunsetSecondary maximum and amplitudescintillations at Delhi. AnnalesGeophysicae, 20, 185-190.Gurubaran,S. and R.Rajaram (1999). Longterm variability in mesospheric tidal windsobserved by MF radar over Tirunelveli (8.7° N 0 , 77.8o E), Geophys. Res. Lett.,26,1113-1116.

Gurubaran, S. and R. Rajaram, (2000).Signatures of equatorial electrojet in themesospheric partial reflection drifts overmagnetic equator, Geophys. Res. Letts.,27, 943-946.

Gurubaran, S. and R. Rajaram, (2001).Mean winds, tides, and gravity wavesduring the westward phase of themesopause semiannual oscillation(MSAO), J. Geophys. Res., 106, 31817-31824.

Gurubaran, S., T. K. Ramkumar,S.Sridharan and R. Rajaram, (2001).Signatures of quasi-2-day planetary wavesin the equatorial electrojet: results fromsimultaneous observations of mesosphericwinds and geomagnetic field variations atlow latitudes, J.Atmos. Solar-Terr. Phys.,63, 813-821.

Gurubaran, S., S. Sridharan, T. K.Ramkumar and R. Rajaram, (2001). Themesospheric quasi-2-day wave overTirunelveli (8.7 N), J. Atmos. Solar-Terr.Phys, 63, 975-985.

Gokarn S.G., G.Gupta, C.K.Rao andC.Selvaraj (2002). Electrical structureacross the Indus-Tsangpo suture and theShyok suture zones in NW Himalayausing magnetotelluric studies, GeophysRes Lett, 29(8)1-4.

Gokarn S.G., C. K. Rao, and GautamGupta, (2002). Crustal structure in theSiwalik Himalayas using magnetotelluricstudies, Earth Planets Space, Vol. 54 (No.1), pp. 19-30.

Gokarn S.G. , C.K. Rao, Gautam Gupta,B.P. Singh and M. Yamashita, (2001)."Deep crustal structure in the Damoh-Jaba lpur -Mand la r eg ion us ingmagnetotelluric studies. Geophys. J.International, 144, 685-94.

Gokarn S.G., C.K.Rao, G.Gupta andB.P.Singh (2001) Magnetotelluric studiesin some seismically active regions inIndia. Research Highlights in EarthSystem Science, Vol.2, Earth SystemScience Division, Deptt of Science andTechnology, New Delhi, pp253-266.

Gokarn S.G. and B.P.Singh, (2000).Magnetotelluric techniques. ResearchHighlights in Earth System Science, Vol.1,Earth System Science Division, Deptt ofScience and Technology, New Delhi,pp123-142.

Gopalakrishnan V. and Kamra A.K.,Estimate of the background aerosolpollution from the electrical conductivitymeasurements in the Indian Ocean, VayuMandal, 29, 230-233, 1999.

Gopalakrishnan V. and Kamra A.K.,(1999)Measurements of the atmosphericelectric field and conductivity made overIndian Ocean during December 1996-Januiary 1997, Current Science, 76, 990-993, 1999.

Haider S A, Seth S P and Raina K S, Fieldaligned current and parallel electric fieldbetween magnetosphere and ionosphere ofMars, Ind. J Radio & Space Phys., 28, 36-42, 1998.

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Hari Om Vats, M.R. Deshpande, M.Mehta, K.N. Iyer, K.J. Shah and C.R.Shah, (1999) Variability of the SolarCoronal Rotation, Adv. Space Res. Vol.24, No. 2, pp. 241-244.

Hari Om Vats, M.R. Deshpande, M.Mehta, C.R. Shah and K.J. Shah, (1999)Radio emission as a diagnostic for solarcoronal rotation, Bull. Astr. Soc. India 27,61-63.

Hari Om Vats, J.R. Cecatto, M. Mehta,H.S. Sawant and J.A.C.F. (2001). Neri,Discovery of Variation in Solar CoronalRotation with Altitude, AstrophysicalJournal, Lett. 548, 87-89.

Hari Om Vats, H.S. Sawant, Rupal Oza,K.N. Iyer and Ravi Jadhav, (2001).Interplanetary scintillation observationsfor the solar wind disappearance event ofMay 1999, Jou. Geophys. Res.(SpacePhysics), 106, 25121 – 25124.

Hari Om Vats, Som Sharma, R. Oza, K.N.Iyer, H. Chandra, H.S. Sawant and M.R.Deshpande, (2001). Interplanetary andterrestrial observations of an earth directedcoronal mass ejection, Radio Science, 36,1769-1773.

Hari Om Vats, R. M. Jadhav, K. N. Iyerand H. S. Sawant, Coronal mass ejectionand Interplanetary Scintillation, Multi-wavelength observations of coronalstructure and dynamics eds. P. C. H.Martens and D. P. Cauffman, COSPARColloquia Series Vol. 13, 317-318, 2002.

Hari Om Vats, Sharma S, Oza R, Iyer KN, Chandra H and Deshpande M R,(2001). Interplanetary and terrestrialobservations of an earth directed coronalmass Ejection, Radio Science, 36, 1769-1773.

Hari Om Vats, Som Sharma, R. Oza, K.N.Iyer, H. Chandra, H.S. Sawant and M. R.Deshpande (2001).Interplanetary andterrestrial observations of an earth directedCoronal Mass Ejection Radio Sci.,36,1769-1773.

Harsha Jalori, and A.K.Gwal, (2001). Roleof magnetic shear on the electrostaticcurrent driven ion cyclotron instability inthe presence of parallel electric field,Pramana, 56(6), 779-784.

Harsha Maru, Sushil Kumar andA.K.Gwal, (1999). The role of fieldaligned currents in presence of parallelelectric field on the generation of whistlermode wave in the magnetosphere, IndianJ. Radio & Space,28, 95-102.

Jadeja A.K., R.M. Jadav, Hari Om Vatsand K.N. Iyer, (2001). Study of TravellingIonospheric Disturbances using IPS Arrayat Rajkot, Indian J Radio Space Phys., 30,457.

Jadeja A.K., R. M. Jadav, Hari Om Vatsand K. N. Iyer, (2001).Study of travelingionospheric disturbances using IPS arrayat Rajkot, Indian Journal of Radio &Space Physics, 30, 249-253.

Jadhav Geeta, Mita Rajaram and R.Rajaram, (2000). Identification of externalcurrent variations in Oersted data,Published in the Proceedings of the thirdOersted International Science TeamMeeting, ed: T. Neubert and Pascale Ultre-Guerard, May 2002.

Jadhav Geeta, Mita Rajaram and R.Rajaram, (2001). Modification of daytimecompressional waves by the ionosphere:first results from Oersted, Geophys. Res.Letts, 28, pp.103-106.

Jadhav Geeta, Mita Rajaram and R.Rajaram, (2002). Main field control of theEquatorial Electrojet: a preliminary studyfrom the Oersted data, J. of Geodynamics,33, 157-171.

Jadhav Geeta, M. Rajaram and R.Rajaram, (2002). A Detailed study ofEquatorial Electrojet phenomenon usingØrsted satellite observations, J. Geophys.Res., 107, SIA 12-1 to SIA 12-12,10.1029/2001JA000183, 10 August 2002.

Jani, Y.N., H.P. Joshi and K.N. Iyer,Seasonal Diff. of Non-migrating tides introposphere & lower stratosphere over

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Gadanki, Indian J Radio Space Phys, 29,210-221, 2000

Jivani, M.N., K.N. Pathak, Boby Mathew,H.P. Joshi and K.N. Iyer, (2000). Effect ofionospheric plasma irregularities oncommunication system parameters, IETETechnical Rev. 17, 43 – 50.

Jivani M.N. and K.N. Iyer, Associationbetween ionospheric scintillations andequatorial electrojet, Journal of the I.G.U.4, 7-12, 2000

Joshi Indira, Paul Priscilla and Tillu A.D.,(2002). Association between geomagneticactivity and surface temperature, IndianJournal of Radio and Space Physics, 31,104-106.

Jayanandperumal R., A.K. Dubey, S.J.Sangode and K.V.V. Satyanarayana,(2001). Superimposed folding, finite strainand magnetic lineation in the MussoorieSyncline, Lesser Himalaya: implicationsfor regional thrusting and Indian platemotion. Himalayan Geology, V.22,pp.207-216.

Kamra A.K., Murugavel P., Pawar S.D.and Gopalakrishnan V., (2001).Background aerosol concentration derivedfrom the atmospheric electric conductivitymeasurement made over the Indian Oceanduring INDOEX, Journal of GeophysicalResearch, 106, 28643-28652.

Kane R. P., Hari Om Vats and SawantH.S., (2001). Short-term periodicities inthe time series of solar radio emissions atdifferent solar altitude, Solar Physics 201,181-190.

Kim, V.P., V.V. Hegai, and M. Lal,(2002). A modeling study of the nighttimeequatorial E-region behaviour duringmagnetospheric substorms and storms, J.Geophys. Res, 107, No. 5.

Krishna Moorthy K., Niranjan K.,Narasimhamurthy B., Agashe V.V. andKrishna Murthy B. V. , (1999)AerosolClimatology over India, AerosolClimatology over India, ISRO – GBP SR03 99, ISRO Publication, pp.1-30.

Kulkarni M.N. and Kamra A.K.,(2001).Vertical profiles of atmosphericelectric parameters close to ground,Journal of Geophysical Research, 106,28209-28222.

Lal, M., (2001). A model study of theatmospheric heating rates due to O3, H2Oand O2, Ind. J. Radio & Space Phys, 30, p.254 – 259.

Lakhina, G. S. and B. T. Tsurutani,(1999). A generation mechanism for thepolar cap boundary layer broad badplasma waves, J. Geophys, Res., 104,279-292.

Lakhina, G. S. and B. T. Tsurutani,(1999). Broadband plasma waves in themagnetopause and polar cap boundarylayers, Surveys in Geophysics, 20,377-414.

Lakhina, G. S., (2000). MagneticReconnection, Bull. Astr. Soc. India, 28,593-646.

Lakhina, G. S., B. T. Tsurutani, J. K.Arballo, and C. Galvan (2000), Sun-Earthconnection: boundary layer waves andauroras, PRAMANA – J. Phys., 55, 665-683.

Lakhina, G. S., B.T. Tsurutani, H. Kojima,and H. Matsumoto, (2000), BroadbandPlasma Waves in the Boundary Layers, J.Geophys. Res., 105, 27,791 – 27,831.

Lakhina, G.S, (2001). Role of heliconmodes in the injection of oxygen ions inthe ring current, J. Atmos. Solar Terres.Phys., 63, 481-487.

Lakhina, G. S. and S. Alex, (2002). Spaceweather research in India: An overview,Indian J. Radio and Space Phys., 337-348.

Lalmani, Madhu Kaul Babu, RajouKumar, Rajesh Singh and A.K. Gwal,(1999). Extremely small dispersionwhistler and VLF emissions recordedduring day time at Jammu, Indian J.Radio and Space Physics, 28, 216-220.

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Sushil Kumar and A.K.Gwal, (2000). VHFionospheric scintillation at equatorialanomaly crest: Solar and magnetic activityeffects, J.Atmos. Terr. Phys., 62, 157-167.

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Hydrological Sciences

S.N. RaiNational Geophysical Research Institute, Hyderabad – 500 007

Introduction

India, being a vast country, ischaracterized with a variety of climaticenvironment ranging from Thar desert ofRajasthan in Western India to the region ofworld’s heaviest rainfall i.e., Cherapunjeein Eastern India; snow covered peaks ofHimalayan mountains in the North to thearid/semi arid regions of southern Plateau.The demand of water supply is increasingday by day to meet the pace ofdevelopments in domestic, agricultural andindustrial sectors. It has to support theneeds of 16% world’s population withmerely 4% of world’s water supply.Vagaries of monsoon and withdrawal ofgroundwater in excess to replenishment ofaquifer system in many parts of Indiaresult into continuous declining of watertable, causing reduction in water supplyand deterioration of its quality. Theproblem is many folds in hard rock regionswhere the water table has gone downbelow the weathered zones and isavailable only in fractured zones. Theaquifer systems in many hard rock as wellas alluvium areas have been overexploited. Therefore, to ensure thesustainable water supply for different usesseveral governmental and non-governmental organizations have carriedout investigations and researches forassessment, development and managementof surface and groundwater resources.This report presents a brief account of theworks in different disciplines of hydrologywhich includes groundwater assessmentand development, water quality,groundwater recharge, rainfall-runoff,flood, sedimentation and glacier’shydrology.

Groundwater resources assessment &development:

Assessment of groundwater potential indifferent parts of the country has beencarried out by using geophysical methods,

remote sensing techniques and GIS.Identification of fractures/lineaments andhydro-geomorphological units areprerequisite for undertaking groundwaterassessment and development in anyregion. Aeromagnetic data have beeninterpreted to delineate ground waterbearing structures in the form oflineaments in a hard rock region at thejunction of two river basins, viz.Marvanka basin and Chitravati basincovering a total area of 400 sq. km. Anew electrical tomography technique istested in the hard rock regions of Dindigulin Tamil Nadu to locate the suitableborehole sites. This technique involvesseries of traverses with the electrodespacing being increased with eachsuccessive traverse. The measuredresistivity is used to construct a contouredsection displaying the variation ofresistivity both laterally and vertically overthe section. It provides a detailed view ofsubsurface structure than by othergeophysical techniques. Geophysicalsurveys comprising deep electricalresistivity soundings, gravity and magneticsurveys were carried out in Sivagangaarea, a part of Cauvery sub basin in TamilNadu, to delineate deeper aquifers.Electrical survey has been carried out todelineate the groundwater potential zonesin an area of 224 sq. km. located in thesouthern part of Chandrapur district ofMaharashtra. Hydrogeological andgeophysical investigations have beencarried out in other parts of the countrysuch as Maheshwaram watershed situated30 km south of Hyderabad, Sonbhadradistrict of Uttar Pradesh, Kandivalasa riversub basin in Vizianagaram district ofAndhra Pradesh, parts of Alwar districtand Shahabad block of Baran district inRajasthan, north western part of Cuddapahb a s i n i n A n d h r a P r a d e s h ,Kerala/Idamalayar lineament coveringparts of Palghat and Trichur districts inKerala, Pageru river basin in AndhraPradesh, a watershed covering Indian

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Aluminum Company Ltd. near Belgaumcity in Karnataka, in and aroundDhenkanal town in Orissa, GujaratRefinery area in Vadodara district ofGujarat, National center for Plant GenomeResearch campus of JNU, New Delhi, MC Tanda watershed located in graniticterrain in Anantapur district andKallugotla watershed located insedimentary terrain in Kurnool district ofAndhra Pradesh. Artificial NeuralNetwork (ANN) approach has been usedto interpret the DC resistivity data fromPuga valley in Ladakh district of Jammuand Kashmir state. The ANN approachhas been found to be fast method for layerthickness and layer resistivity estimation.

Exploratory drilling is the most effectivemeans of exploration for locating,assessing and evaluating the groundwaterpotential. Central Groundwater Board(CGWB) has been conduct inggroundwater exploration studies in manyparts of the country by the construction ofexploratory wells, observation wells, slimholes and piezometers. From a network ofabout 15000 stations, the CGWB monitorsthe positions of groundwater levels fourtimes in a year in the month of January,April/May, August and November. InAndhra Pradesh alone the CGWB, till2002, has drilled 1927 bore holes, 926exploratory wells, 891 observation wells,14 slim wells and 265 piezometers. Themaximum depth of exploration carried outin this state so far is 750 m in the soft rockareas piercing Tertiary and Gondwanaformations. In the hard rock areasmaximum depth drilled was 300 m.

A software package is developed on FoxPro version 2.5 to evaluate the GroundWater Potential Index (GWPI). Thepackage has the facilities to declare thetitles of the parameters that influence theground water potential, to create data base,to create a model by performing thestatistical and regression analyses, to drawa graph and to predict the groundwaterpotential of a given area. The computerpackage has been developed such thateach time when the ratings and weightsgiven to each of the parameters of a givensite according to their importance in

groundwater exploration are suitablymodified by the user during the modelcalibration, the program performs all thenecessary operations and gives the endresults accordingly. It is demonstrated thatthe results obtained with the help of thiscomputer software package are tallyingwith the results obtained through manualprocessing.

Field observation and analysis of pumpingtest data of dug wells in parts of Nasikdistrict show that dykes act as potentialaquifers when they are jointed/fractured.An integrated geophysical approach hasbeen applied to identify structural featuressuch as fractures, weak zones and intrusivedyke bodies which can control and hostpotable groundwater at greater depth in anarea of about 8 sq. km along the east coastof Tamil Nadu which has been identifiedas a major rain shadow zone.

Water quality

The quality of water is of vital concern tothe mankind, as it has direct link withhuman health. Therefore, pollution ofsurface/ground water is another majorproblem, which has attracted the attentionof scientists, engineers and planners.Groundwater pollution has been growingincessantly in several parts of the country,particularly in areas of intensiveindustrialization. Many industriesdischarge their untreated waste in theimmediate neighborhood or in some nearby low lying areas mostly in openchannels which join various surface waterbodies such as large ponds, streams, riversetc. The pollutants of these wastematerials seep down to the groundwatersystem along the entire course of fluidflow. The Ganga alluvial plain is one ofthe largest groundwater repositories of theEarth. For several decades the drainagebasin of the Ganga plain has been used forthe disposal of domestic and industrialwastes which has adversely affected thequality of water, sediments andagricultural soil of the plain. A study hasbeen carried out to know the status ofanthropogenically induced metal pollutionin the Kanpur – Unnao industrial region ofthe Ganga Plain. This study indicates that

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the water and soil of this region is highlypolluted by various metals.

Based on hydrochemical investigation ofwater samples from northwestern parts ofRanga Reddy district in Andhra Pradesh(A.P.) the water is characterized as hard tovery hard class. The hardness is due topresence of Ca and Mg carbonates.Similar hydrochemical investigations havebeen carried out in different problematicregions of the country to quantifygroundwater quality. Examples can becited from a portion of Ghataprabha leftbank canal command area in the Belgaumand Bagalkot districts of Karantaka,Hardwar district of Uttaranchal, Sakri andPanchana rivers basins in Newada districtof Bihar, suburban areas of Hubli inKarnataka, Rewa region in MadhyaPradesh, Pageru river basin in Cuddapahdistrict and Enumula Vagu sub basinunder Dindi river basin in Mahaboobnagardistrict of A.P., Salem magnesite area inSalem district of Tamil Nadu, Patancheruindustrial area in A.P., Ganga Alluvialplain in Etah district of U.P., KrishnaDelta in A.P., catchment area of Rajghatdam in Lalitpur district of MadhyaPradesh, Jammu district of Jammu andKashmir state, Kodaganar water shed inDindigul district of Tamilnadu, in andaround Dindigul Town, Erode district ofTamil Nadu, Maheshwaram water shed inRanga Reddy district of A.P. , Palar basinin Tamil Nadu, Gujarat refinery in Gujrat,Potharlanka island of Krishna delta in A.P.Water quality monitoring and aquacultureimpact on coastal tracts of West Godavaridistrict of A.P. have been carried out. Thestudy area lies between Godavari andKrishna rivers. Origin and distribution ofNitrate in groundwater from different partof the country have been investigated byCGWB. Some of the major findings of theabove mentioned hydrochemicalinvestigations are given below:

• Fluoride content ranging from0.08 to 2.8 mg/l are found in thestudy area of Newada district withhigher values restricted in Rupan-Kankol belt.

• In Rewa region, the groundwaterfrom shallow zones is suitable fordrinking, and industrial purposes.

• Groundwater of Pageru river basinis good either for drinking or foragricultural purposes.

• In Enumula Vapu basin, the highfluoride rich zones of dug wellslocalized around Kondareddy palliand Tippareddy villages.

• Water in and around thePatancheru industrial area iscontaminated showing very highconcentration of heavy toxicmetals than that of permissiblelimit prescribed by WHO.

• The groundwater in parts of Etahdistrict is alkaline, hard andmoderately mineralized. Theheavy metals concentration in theshallow aquifers is above thepermissible limit whereas in thedeeper aquifers concentration iswell within the limits.

• Groundwater of north Krishnadelta is more polluted than thesouth delta and in this region 24%dug wells and 18% hand pumpshave exceeded the limits. Thepossible source of high nitratelevel in groundwater has beenidentified as excessive utilizationof nitrogenous ferti l izers,insecticides and pesticides foragricultural purposes.

• Water samples from in and aroundDindigul have shown very highvalues for Na, Cl, Ca, So4 andNO3 indicating the influence ofthe effluents of the tanneries.Groundwater from an area ofabout 50 sq. km around Dindigulhas became unfit for drinking andirrigation.

• The water quality monitored in 45wells in the region of Gujaratrefinery indicates groundwatercontamination from anthropogenicsources. TDS, sodium andchloride concentration are foundto be high and show a consistentspatial variation.

Pollution potential index for the Musi riversub basin from Amberpet to Nallacheruvu

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in Hyderabad city has been evaluated.From the analysis it is found that when weface downstream of the Musi nearAmberpet, all along the left bank of theMusi is more susceptible for pollution.This has been ably confirmed byhydrogeochemical investigations carriedout in the study area. Major ionconcentration including fluoride wereanalysed from 92 samples collected in andaround the twin cities of Hyderabad andSecunderabad during June 2000. Theresults show that more than 60% ofsamples have fluoride exceeding 1.5 mg/l,the higher limit prescribed by WHOincluding a few that cross even 2.5 mg/l.In general, the deep aquifers are potable,but since they are connected to shallowaquifers as well as surface water bodiesand also due to indiscriminant pumping,migration of pollutants to these aquiferscannot be ruled out.

Studies carried out on trace elements (Cu,Fe, Zn, Mn and Pb) geochemistry ofgroundwater from Behedi basin in Nasikdistrict of Maharastra have shown spatialas well as temporal variations of theseelements. Weathering of rocks and thehuman activities have been identified asthe main sources of trace elements in thegroundwater. Intensive use ofmicronutrient fertilizers in associationwith the use of pesticides have lead tohigher concentration of trace elementsunder irrigated agriculture than the otherland use types. This study suggestschemical fertilizers as potential source oftrace element pollution of groundwater. Inan attempt to evaluate the impact ofirrigation on quality of groundwater, 136samples from Sangamner area inAhmedanagar district of Maharashtra havebeen analyzed. The investigationssuggest that excessive use of fertilizersand irrigation water in a terraincharacterized by low flushing rates,presence of alluvium and flat topographyhave caused deterioration of groundwaterquality. Similar studies have been carriedout to quantify the groundwater qualitydeterioration caused by improperagricultural practices, mainly due toexcessive use of fertilizers and pesticidesin other parts of the country.

Geophysical investigations carried out inthe Mettupalyam industrial state inPondicherry have revealed a number ofcontaminated zones due to indiscriminatedischarge of effluents from the chemical,paper and metal industries in the opendrains or on the ground. These effluents,which have found their way intogroundwater region, started migratingalong with ground water flow.Groundwater quality characterization andpollution vulnerability in Ghaziabad urbanarea of U.P. has been investigated.Protection strategies to mitigate thepollution problems of the area on long-term basis have been suggested. Theoccurrence of high concentration offluoride in groundwater (1.5 mg/l) in thevillages of Singpur Sagarajan in theNayagarh district of Orissa and its relationwith the fluoride rich hot spring water(10mg/l) located near by have beenstudied. The topography of the area hasexerted a control on the aerial extent offluoride contamination. Concentration ofheavy metals (Cd, Fe, Cr, Mg, Pb and Zn)have been evaluated at nine spring waterand eight surface water sampling locationsnear the limestone mining area of Sirmourdistrict of Himachal Pradesh during preand post monsoon seasons. This studyshows that the water in this region is notpolluted with respect to heavy metalsdespite the prolific growth of limestonemining in this region.

An analysis of groundwater flow andtransport processes of arsenic in the flowdomain of Yamuna sub basin located inWest Bengal is carried out. The studyindicates that the occurrence of arsenic at alocation has no correlation with thetransport of arsenic from other sources;rather it indicates that there is spreading ata localized scale due to transport of in-situactivation. Capture zone analysis does notshow encouraging results for removingarsenic through a specific set of clean upwells. Geochemical properties ofgroundwater from Nadia district in WestBengal have been analyzed to interpretarsenic contamination of groundwater.The appearance of arsenic and chemicalextent of the deterioration in groundwaterquality of the Rajnandgaon district of M.P.

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has been reported. Total arsenicconcentration obtained in the analysisranged between 0.01 – 1.01 mg/l. Thenumber of people at risk is 10,000.Contamination of groundwater due tofluoride is reported from many places ofAndhra Pradesh, Tamil Nadu, Karnataka,Gujrat, Rajasthan, Punjab, Haryana, Biharand Kerala. A high concentration of 5.2mg/l has been reported in Medak districtof A.P., 15 mg/l in Nawabganj block,Uttar Pradesh and 18 mg/l in Jaipur,Rajasthan as against the critical limit of1.5 mg/l in drinking water. The incidenceof very high level of fluoride is in theeastern and southeastern belt of Karnataka,covering districts of Gulbarga, Raichur,Bellary, Chitradurga, Tumkur and Kolar.

An attempt has been made to study theprogression of seawater intrusion intocoastal aquifers of Vakadu mandal inNellore district of A.P. The degree ofcontamination due to saline intrusion wasestimated before and after the monsoon.Due to the increase of aquaculture in andaround west Godavari district, quality ofgroundwater has been a problem in coastaltracts of west Godavari district of A.P.For a better understanding of this problemintegrated surveys, which includehydrochemical studies and statisticalmodeling technique, have been applied inthe region of Kolleru lake. This studyreveals that the indiscriminate andillegitimate expansion of aquaculture inKolleru lake and its environ drasticallyreduced the inflows into Upputern river.Reduction in the inflow resulted intoingression of seawater. A study has beencarried out to investigate groundwaterquality in order to generate baselineinformation on groundwater resources indeveloping urban area of Guntur district inA.P. In accordance with the domestic andindustrial water quality standard groundwater is not suitable for uses.

G r o u n d w a t e r r e c h a r g i n g(natural/artificial)

Harvesting and storage of runoff andrecharging of aquifers in a framework ofintegrated land water development on awatershed basis with community

participation is emerging as a newparadigm due to the recent efforts of bothgovernment and non-governmentorganizations. Under the supervision ofworkers of Tarun Bharat Sangh, anongovernmental organization, Arvaririver in Alwar district of Rajasthan statehas been revived by mean of storage ofrain water in percolation tanks and Johadsconstructed along the bank of the river.Johads are simple concave shaped barriersbuilt across the slope to arrest rainwaterwith high embankment on three sideswhile the fourth side is left open for therain water to enter. For this purpose 4500Johads in 1050 villages has been built. Asa result of this water table in this regionhas been raised by 5 to 8 meters. Apartfrom Arvari river four more streams havebeen revived. Similar experiments ofgroundwater recharging through rainwaterharvesting have been executed at someother places. The average natural rechargeto the aquifer of Kongal river basin locatedin Nalgonda district of A.P. due to 1993-94 monsoon is estimated by Kriging andThyson polygon methods. The estimatedrecharge is 5% of the rainfall.

Recharge measurements using Tritium(tracer) injection technique were carriedout in 16 study areas located in graniteterrain. It indicates annual rechargevarying from 25 mm/y to 159 mm/y withan average annual recharge of about 80mm/y or about 10% of the seasonalrainfall. A linear relation between rainfalland natural recharge is observed forseveral watersheds/basins. Twop e r c o l a t i o n p o n d s , o n e a tKarthikeyapuram and another at SanthanVenu Gopalapuram in Tamil Nadu wereobserved for three years to assess theirpotential influence zone. An artificialrecharge structure has been constructed ona granitic terrain to augment and improvethe groundwater quality by diluting thefluoride rich aquifer of the Jawalgeravillage in Raichur district of Karnataka.The scheme has brought down the fluoridelevels from 1.9 to 1.1 mg/l within a year.A subsurface dam was constructed acrossa stream in a small watershed measuring2.34 sq. km at Gaurelli village of R.R.district in A.P. The impact assessment

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study indicates that the construction of thedam enabled to conserve additionalgroundwater. Also there was considerablereduction in fluoride concentration in thegroundwater.

A pilot project on developing agroundwater sanctuary for drinking waterin wasteland at Gurukanipalle village inChittoor district of A.P. was executed.Estimation of recharge using Tritiumtracer technique indicates that 13.6% ofseasonal rainfall percolates down toreplenish the shallow groundwater regime.Another project was executed in DhanautiBadi village in Churu district of Rajasthanto harness the surplus runoff for artificiallyrecharging the groundwater to create apotable groundwater source and toimprove the groundwater quality bydilution of fluoride content.

To evaluate the efficiency of Kalwakurtypercolation tank situated in granitic area ofMahaboobnagar district in terms of itscontribution to the groundwater regime,the technique of environmental chloridemass balance in tank water as well as indownstream well water is employed.Through this technique it is estimated thatthe tank contributes about 21000 Cu. m. ofimpounded water to the groundwater withan efficiency of 44% artificial recharge.The environmental chloride profiling iscarried out at six sites in Maheshwaramwatershed near Hyderabad in A.P. toestimate the recharge. The total rechargeis estimated to be 10% of the annualrecharge. Hydrogeological andgeophysical investigations have beencarried out in 44 villages of Pakur districtsin Jharkhand state to select suitable sitesfor the construction of checkdams/percolation tanks. Based on theseinvestigations sites were selected forconstruction of these structures.Percolation tanks and check dams havebeen constructed in many parts of thecountry for the replenishment of aquifer.

For the entire Ranga Reddy district of A.P.an integrated study has been undertakenon the basis of drainage network, surfacetopography, structural geological featuresand surface storage source (tanks).

Thematic maps for all these aspects havebeen prepared and overlapped using GISto arrive at their interrelationships in termsof groundwater distribution. The presentstudy has clearly brought out distinctgroundwater mounds, signifying areas ofpotential recharge. The present studybrought out a correlation between thelineaments and groundwater mounds.This study indicates that Ghatkesar,Hayatnagar, Ibrahimpatnam, Marplace,Moinpeta, Vikarabad mandals are the bestareas for the development of rechargingactivities.

Modeling of groundwater flow and masstransport

Mathematical models play key role inassessing the dynamic behaviour of agroundwater system to various schemes ofrecharging/pumping and other stresses andin selecting an appropriate one out ofmany proposed schemes for sustainabledevelopment of groundwater systems.Knowledge of the dynamic behaviour ofgroundwater flow is also essential toassess the extent of spreading of hazardoussubstances from the source ofcontamination. Such knowledge helps infinding out some ways and means toprevent or at least minimize the spreadingof pollutants. In the last four years boththe numerical and analytical mathematicalmodels have been developed to understandthe dynamic behaviors of groundwaterflow and pollutant transport in differentparts of the country in order to suggestremedial measures to protect the regionalwater balance and quali ty ofgroundwater/surface water bodies.Numerical mathematical models havebeen developed to understand the nature ofgroundwater flow and pollutant migrationin the region of Gujarat refinery.Distributions of hydraulic head andcombined concentration of sodium andchloride have been computed for the year2000. The prediction of pollutantstransport has been made for the year 2005and 2015.

Groundwater flow and mass transportnumerical model of the MettupalyamIndustrial Estate and its environ covering

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Muttarpalyam well field has beendeveloped. The computed values ofsulphate concentration are matchingclosely at all the observation wells. Toassess further migration of contaminantstowards the Muttarpalayam well field, it issuggested to drill some more wells alongthe southern boundaries of the industrialestate for abstraction and treatment of thecontaminated groundwater for industrialuse. This may help in containing spread ofthe contaminant plume towards theMuttarpalayam well field. Numericalmathematical model has been developed tostudy the impact of Bansagar reservoir ongroundwater seepage to Kuteshwarlimestone mines in Jabalpur district ofM.P.

A numerical model combining thetransport with the equilibrium aqueousgeochemistry is developed for simulatinghydrogeochemical behaviour observed ingroundwater system. The model is capableof considering ion exchange, precipitation,dissolution, redox and acid-base reactionsoccurring in groundwater. The model isapplied on three field problems todemonstrate it’s applicability in analyzinggroundwater system influenced bytransport and geochemical reaction. Thefirst problem corresponds to an ionexchange case; the second pertains to thechemical concentrations pattern evolvingfrom complex changes in chemicalcompositions resulting from precipitationand dissolution of carbonate minerals.The third problem deals with the oxidationof pyrite in the Vadose zone of minestailing which result in acidic drainageconditions along with associated leachingof dissolved metals into the groundwatersystem.

Groundwater in the Palar basin is gettingdeteriorated due to indiscriminate disposalof wastes from tanneries and industries.Mathematical modeling has been carriedout to estimate the variation ofgroundwater heads for various proposedschemes of groundwater resourcesdevelopment in order to know thedirection of flow of pollutants. Anumerical mathematical model has beenconstructed to gain a comprehensive

understanding of the groundwater systembehaviour in Vattigudipadu watershed inKrishna district of A.P. Numerical resultsindicate that there will be decrease ingroundwater storage because ofcontinuous over exploitation ofgroundwater.

A numerical mathematical model has beendeveloped for inverse modeling ofgroundwater systems using the GenericAlgorithm (GA) approach. The model canbe successfully applied for aquifer systemswhere data available may be sparse andwith errors. The developed model is usefulfor parameter estimation with littleavailable field information. Agroundwater flow model of the aquifersystem of Kanchanapally watershedspreading over 11 km in Nalgonda districtof A.P. was calibrated under transientconditions using monthly rechargeestimates of the water balance model. Theaverage groundwater recharge is found tobe 86.7 mm/y for an average annualrainfall of 759.6 mm/y. The output of therecharging process model was found veryuseful to simulate dynamic variations ofrecharge in a groundwater flow modelwhile giving input at monthly intervals.

Based on the Galerkin Finite Elementnumerical formulation, a computerprogram, named FEMTRAN is developedto describe the groundwater flow and masstransport. After verification against theresults of 1-D and 2-D analytical solution,the program is applied to a field problemto analyze the contamination of thegroundwater due to discharge of effluentfrom Mulla sugar factory located inAhmednagar district of Maharashtra.

Simulation of seawater intrusion in asection of Ernakulam coast throughsaturated unsaturated (SUTRA) model hasbeen carried out to examine the impact ofincreased pumping scenario on the extentof seawater intrusion. This study revealsthat the sensitive zone (salinity more than500 mg/l) in this area is between 440 m to2000 m from the high tide line. Therefore,any groundwater development activities inthis area need to be carefully planned with

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remedial measures to contain furtherintrusions.

A 2-D solute mass transport model withvertical cross section of the Kavarattiisland in the Arabian sea off the westerncoast of India was constructed by usingcomputer code SUTRA. The modelanalysis shows that the salinity ofgroundwater continues to increase unlesspumping is kept below a certain rate.Groundwater potential can be augmentedby reducing the subsurface outflow to thesea and by raising the water table by asubsurface dam.

Numerical models are mostly used tosolve the real field problems. However,before application to field problems, theirvalidity has to be checked either bycomparing the numerical results with theobserved data or with the results ofanalytical models. Mostly analyticalmodels were developed to describe watertable fluctuation in response to constantrate of recharge. However, the rate ofrecharge like infiltration rate is known tovary with time due to several factors.Initially swelling and dispersion of the soilparticles beneath the recharge basinreduces the infiltration rate for a shortduration and then it increases to amaximum value due to release ofentrapped air in soil pore. After that theinfiltration rate decreases again due tosediment and biological clogging. Therate of recharge follows approximately asimilar pattern of variation but with lessintensity and some time lag. Byconsidering such variation in recharge rateas well as in pumping rate analyticalmodels have been developed to predict thewater table fluctuation in different flowsystems characterized by different kinds ofinitial and boundary conditions. The rateof recharge/pumping is approximated by anumber of linear elements of differentlengths and slopes depending on the natureof variation in the recharge and/orpumping rates. In this schemerecharging/pumping can be consideredfrom any number of basins/wells of anydimensions located any where within theflow domain but away from the boundary.Analytical models have also been

developed to describe the water tablevariation in response to exponentiallydecaying recharge rate in leaky aquiferand to describe the nature of stream -aquifer interaction. Analytical modelshave been developed in stochasticframework to describe water tablefluctuation by taking into account therandom nature of aquifer parameters.Analytical models have been alsodeveloped to describe the spreading ofpollutants from the source regions.

Rainfall-runoff, Flood, Sedimentationand Glacier’s Hydrology:

Rainfall data are measured at more than3000 stations spread over different part ofthe country by the Indian MeteorologicalDepartment (IMD). The Central WaterCommission (CWC) operates a network ofabout 877 hydrological observationstations for collection of gauge discharge,silt and water quality data for planning andmanagement of water resources projects.CWC also operates 132 flood-forecastingstations to cover most of the flood pronerivers. An analysis is made to studywinter rainfall pattern in the southernIndian region and its relation to thecyclonic storms in the Bay of Bengal. Forthis purpose, data for the year 1901 – 2002have been analyzed. This analysis showsthat in winter the highest seasonal rainfallis recorded in Tamil Nadu and the leastrainfall is in coastal Karnataka and northinterior Karnataka. The variability ofrainfall is the highest in the subdivisions ofKarnataka and the least is in Tamil Nadu,Kerala and Lakshaweep.

Runoff is the most basic and importantdata needed for planning water controlstrategies/practices, such as storagefacilities, erosion control structures etc.The most popular method used for runoffestimation is SCS runoff curve numbermethod. An attempt has been made tocompute runoff for the Neeralipallamwatershed located in Nilgiri district ofTamil Nadu by using the daily rainfalldata, estimated runoff curve number andremote sensing imageries. From therainfall and runoff values it is noted thatthe study area is influenced by both the

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monsoons i.e. southwest and northeast.The northeast monsoon (Oct. – Dec.) isdominated over the southwest monsoon(June – Sept.), as there is more runoff inthis season. These values of rainfall-runoff are very useful for the propermanagement of watershed.

A study was undertaken to comparecomposite and distributed curve number(CN) techniques for estimation of runoffto a medium size agricultural watershed,namely Tarafeni (138.06 km2), located inWest Bengal. The pertinent observationsfrom the study revealed that the percentincrease in runoff is very high for smallevents, moderate for medium and low forhigh rainfall events. This studyrecommends the distributed CN Techniquewith initial abstractions (Ia) = 0.2S (s isthe maximum potential retention). Gurpurriver basin of Dakshin Kannada district ofKarnataka State has been chosen as a testsite to demonstrate the capabilities ofGeographical Information System (GIS)coupled with Remote Sensing (RS) data asinput for SCS model in estimating thevolume of runoff. Runoff is computed forfew rainfall events both by conventionallyderived CN and GIS derived CN. Theresults are agreeable thus providing GIS tobe a preferred alternative to conventionalmethods. GIS and Remote Senescing datahave been successfully applied in thedevelopment of proposed urban stormwater management for Kolkata city inWest Bengal. By using an integratedapproach of Remote Sensing (RS), GISand Soil Conservation Service (SCS)model, an attempt has been made toestimate runoff for the Remi watershedsituated in the East Siang district ofArunachal Pradesh. The total averageannual runoff yield of the watershed is347.37 mill. m3. If this much amount ofwater can be harvested properly, then itcan be used for irrigation, domestic andother uses. In another study an attempt ismade to use RS and GIS techniques toidentify suitable sites for water harvestingstructures in Nagulaty forest range ofKurnool district of A.P. Runoff potentialmap is prepared based on curve numbercriteria. Runoff estimation has been madefor the Peddapandyal watershed in

Warangal district of A.P. using RS andGIS techniques.

Complexity of the nature of Indian rainfallrecord has been studied using the ArtificialNeural Network (ANN) model. As anexample annual rainfall data spanning overa period of 1900 – 1986 was trained usingthe concept of ANN and theirpredictability was made successfully for aperiod from 1987 to 1998. The predictedvalues have almost a perfect match withthe actual data.

The frequencies of f loods atgauge/discharge (G/D) sites of Indianrivers have been examined using 14 yearsdata of 1986 to 1999. Only the data ofsuch G/D sites have been consideredwhich have experienced more than 50floods during this period. It is found thatsuch frequent floods do not occur in thecentral and peninsular rivers but only innortheast and north Indian rivers. Innortheast India such floods have occurredin 8 rivers including Brahmaputra at 12G/D sites while in north India 9 riversincluding the Ganga at 20 G/D sites haveregistered more than 50 floods. The worstflood prone sites have been found on theBrahmaputra at Dibrugarh and on the BekiRiver at Road Bridge and on the KosiRiver at Baltara. The magnitude of flooddeviation at different sites has also beenexamined. This study has shown thatenormous water resources are available inthis country, which can be used indeficient rainfall regions through anetwork system of reservoirs and canals.

A proto-type space-based disastermanagement system (DMS) has beenorganized with comprehensive data basedesign, space based near real timemonitoring/mapping tools, modelingframe works, networking solutions andmulti-agency interfaces. With theappropriate synthesis of these elements, asystem-definition of the frame work of aDMS has been arrived at in terms ofdeveloping a methodology towardsdamage assessment due to 1998Brahmaputra floods. The limitedvalidation experiments carried out inconsultation with local level functionaries

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reveal that the experimental results ondamage to agricultural crops due to floodsare in conformity with field condition.

The Himalaya, covering about 17% oftotal mountainous area of the Indiansubcontinent, comprises several importantglacier systems. Himalayan glaciers forma unique reservoir of fresh water, whichsupport mighty perennial river systemssuch as the Indus, the Ganges and theBrahmapurta. Their combined annualrunoff amounts to about 1.19 X 103 km3

and the total suspended sediment loadnearly 1.8 Gt. The Himalayan proglacialstreams carry about 70-85 % of the totalannual river flow, which is derived fromsnow and glacier ice melt, which in turn isrelated to the radioactive energy input,variation in air temperature etc.

Apart from being the source of freshwater,Glaciers have been recognized assignificant agent of erosion anddeposition. Discharge and suspendedsediments were measured throughout theablation seasons between May andOctober 1999 and 2000 in the proglacialstream that drains the Gangotri Glacierinto Ganges river basin. During theobserved periods, the total dischargevolume was estimated to be 581.87 and547.47X106m3 respectively, and the totalsuspended sediment was 165.62 and104.99 X 104 t, respectively. A large partof the total discharge volume andsuspended sediment was contributedbetween July and September when solarradiation is strong. This study indicatesthat the suspended sediment load exhibitsa positive correlation with the dischargevolume on a seasonal scale. However,different sediment rating relationshipswere found for different years under theinfluences of changing patterns of snowand glacier ice melts.

The average contribution of snow andglacier melt runoff in the annual flows ofthe Satluj River at Bhakra Dam isestimated about 50%, the remaining 40%being from rain. Remote sensing throughits spatial, spectral and temporal attributesprovides synoptic and repetitiveinformation on the water spread area of a

reservoir. Using satellite data of variousyears, it is found that on average about14998 km2 (65% of the total drainage area)of the Indian part of Satluj river basin upto Bhakra Dam is covered by snow in themonth of March. After the snowmeltseason in September, about 4528 km2

(20.3% of the total drain area) remainscovered by perpetual snow and glaciers.As such, an area of about 9970 km2

becomes snow free during the melt season.

Sediment particles originating fromerosion processes in the catchment arepropagated along with the river flow.When the flow of the river is stored in areservoir, the sediment settles in thereservoir and reduces its capacity.Reduction in the storage capacity of areservoir beyond a limit hampers thepurpose for which it was designed. Thus,assessment of sediment depositionbecomes very important for themanagement and operation of suchreservoirs. In a study, remote sensingapproach has been attempted forassessment of sedimentation in Bhakrareservoir. Remote sensing data (IRS-1B-LISSII) provided the information on thewater-spread area of the reservoir, whichwas used for computing the sedimentationrate. The loss in reservoir capacity due todeposition of sediments for a period of 32years (1965-1997) was determined to be807.35 Mm3, which gives an averagesedimentation rate of 25.23 Mm3 per year.

An index based approach, based on thesurface factors mainly responsible for soilerosion is used to assess the vulnerabilityto the river Tapti in Surat district ofGujarat state using remote sensing dataand GIS. Two watersheds were identifiedas being the most susceptible to soilerosion. Based on the integrated index, apriority rating of the watersheds for soilconservation planning is recommended.

Suspended sediment concentration in themelt water of Pindari Glacier located inthe Almora district of Uttaranchal state inCentral Himalaya was determined atregular intervals in four ablation seasons.The sediment chemistry of the Glacier isdominated by Si, Al, K, Fe and Mg

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together constituting > 70% of theelemental abundance. The X-raydiffraction study showed that quartz is themost dominant mineral followed byMica/Illite, Feldspar and Kaolinite.Coarse and medium silts predominant inthe size distribution while clay constitutesabout 7% of the total size population. Byuse of remote sensing data in conjunctionwith GIS, assessment of sedimentdeposition in Bargi Reservoir, MadhyaPradesh state has been made. Theresulting sedimentation rate in the zone ofstudy is about 229 m3 of catchment areaper year.

The water balance of the lake Nainital,located in the Kumaun Himalayan regionhas been computed. The mass balanceresults indicate that the groundwatercontribution is about 50% of the totalannual inflow to the lake. The subsurfaceout flow is about 55% of the total annualoutflow from the lake. The waterretention periods for the lake estimated byisotopic mass balance, Chloride massbalance and conventional water balancemethods are about 1.93, 1.77 and 1.92years, respectively.

Water and bed sediment samples collectedfrom the Damodar river and its tributarieswere analyzed to study elementalchemist ry and suspended lowcharacteristic of river basin. Thesuspended sediments show a positivecorrelation with discharge and suspendedload, reach their maximum value duringthe monsoon season. The geo-accumulation values calculated for Fe,Mn, Zn, Ni and Cu are well below zero,suggesting that there is not pollution fromthese metals in Damodar river sediments.

PublicationsAcharya, R.S., Ananda Reddy, R., RajaniKumar, M. and Vittal Rao, K.P.R., 2002.Geophysical surveys for deeper aquifers inSivaganga area, Tamil Nadu: A casestudy. In: Proc. of the IGC 2002, Dindigul,Tamil Nadu, (Eds. M. Thangarajan, S.N.Rai, V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 35-48.

Acharyya, S.K., Lahiri, S., Raymahashay,B.C. and Bhowrnic, A., 2000. Arsenictoxicity of groundwater in parts of theBengal basin in India and Bangladesh: therole of Quaternary Stratigraphy andHolocene sea-level fluctuation, Environ.Geol., 39(10), 1127-1132.

Ahmad, S. and Hasnain, S.I., 2001. Snowand stream water chemistry of the Gangaheadwater basin, Garhwal Himalaya India,Hydrol. Sci. J., 46(1), 103-111.

Ahmad, S. and Husain, S.I., 2002.Hydrograph separation by measurement ofelectrical conductivity and discharge formelt waters in the Ganga HeadwaterBasin, Garhwal Himalaya, J. Geol. Soc.India, 59, 323-329.

Ali, I. And Jain, C.K., 2001. Pollutionpotential of toxic metals in river Yamunaat Delhi, India, J. EnvironmentalHydrology, 9, 1-9.

Ananda Rao, V., Dhakate, R., Singh, V.S.and Jain, S.C., 2002. Delineation ofaquifer geometry in Sukinda Chromitedeposit valley through geophysical andhydrogeological investigation. In: Proc.Intl. Conf. on Hydrology and watershedmanagement (Eds. B. Venkateswara Raoet al.), 18-20 Dec., Hyderabad, 87-96.

Anjaneya Prasad, M., Murthy, A.R., andKumar, M.D.N., 2002. Selection ofsuitable sites for rain water harvestingstructures and runoff potential areas usingGIS and RS. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 514-521.

Ansari, A.A., Singh, I.B. and Tobschall,H.J., 1999. Status of anthropogenicallyinduced metal pollution in the KanpurUanno industrial region of Ganga Plain,India Environmental Geol., 38(1), 25-33.

Anwar, Md., Prem Chand, Ch. andVenkatewara Rao, B., 2002. Evalution ofgroundwater pollution potential of Musiriver catchment using drastic Index model.In: Proc. Intl. Conf. on Hydrology andwatershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 399-408.

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Ashok Kumar and Prasad, L.B., 2002.DSTM & DBTM for estimation of staticand dynamic groundwater reserve in hardrock. In: Proc. Intl. Conf. on Hydrologyand watershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 369-378.

B a n d y o p a d h y a y , R . K . , 2 0 0 2 .Hydrochemistry of arsenic in Nadiadistrict, West Bengal, J. Geol. Soc. Ind.,59, 33-46.

Barker, R., Venkateswara Rao, T. andThangarajan, M., 2003. Application ofelectrical imaging for boreholes siting inhard rock regions of India, J. Geol. Soc.India, 61(2), 147-158.

Bhagavan, S.V.B.K. and Raghu, V., 2002.Application of remote sensing techniquesfor groundwater prospects – a case studyof Kaidampalli watershed, Medak District,Andhra Pradesh. In: Proc. of the IGC2002, Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 99-102.

Bhosale, D.P. and Kumar, C.P., 2002.Simulation of sea water intrusion inErnakulam coast. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 390-399.

Biswas, S., 2003. Groundwater flowdirection and long term trend of waterlevel of Nadia district, West Bengal, astatistical analysis, J. Geol. Soc. of India,61, 22-23.

Chakraborti, D., Biswas, B.K., RoyChowdhury, T., Basu, G.K., Mandal, B.K.,Chowdhury, U.K., Mukherjee, S.C.,Gupta, J.P., Chowdhury, S.R. and Rathore,K.C., 1999. Arsenic groundwatercontamination and sufferings of people inRajnandgaon district of M.P., Curr. Sci.,77(4), 502-504.

Chandra, P.C., Ramakrishna, A., Singh,S.C. and Reddy, P.H.P., 2002.Geophysical approach to delineatesaturated fracture zones in hard rocks. In:Proc. of the IGC 2002, Dindigul, TamilNadu, (Eds. M. Thangarajan, S.N. Rai,V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 75-84.

Chandra, P.C., Srivastava, M.M.,Mohd.A., Bhowmic, M.K., Pandey, K.S.,Haq, S. and Singh, U.B., 2002.Geoelectr ical invest igat ions forgroundwater in Quartzitic sandstones andgranites of Sonbhadra district, UP. In:Proc. Intl. Conf. on Hydrology andwatershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 111-119.

Chandrasekharan, H. and Navada, S.V.,2002. Interconnection between waterbodies in select areas of Rajasthan state,India. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 183-192.

Chauhan, S.S., 2002. A review ofgroundwater exploration in AndhraPradesh. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 120-127.

Chidambaram, S., Ramanathan, A.L.,Srinivasamoorthy, K. and Anandhan, P.,2002. Studies on groundwater quality ofhard rock aquifer of Erode district - a casestudy. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 305-316.

C h o u r a s i a , L . P . , 2 0 0 2 .Hydrogeochemistry of groundwater inalluvial plain of northern Madhya Pradesh,India. In: Proc. Intl. Conf. on Hydrologyand watershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 217-226.

Chourasia, L.P., 2002. Hydrogeochemicalstudies of groundwater in catchment areaof Rajghat dam project, India. In: Proc. ofthe IGC 2002, Dindigul, Tamil Nadu,(Eds. M. Thangarajan, S.N. Rai, V.S.Singh), IBH & Oxford Publ. Co., NewDelhi, 317-326.

Das, B.K., 1999. Environmental pollutionof Udaisagar lake and impact of Phosphatemine, Udaipur, Rajsthan, India. Environ.Geol., 38(3), 244-248.

Deshmukh, K.K. and Pawar, N.J., 2000.Impact of irrigation on the environmental

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geochemistry of groundwater fromSangamner area, Ahmednagar district,Maharashtra. Proc. of ICTWRM, 19-21Dec., New Deli, India, 519-531 pp.

Despande, R.D., Bhattachrya, S.K., Jani,R.A. and Gupta, S.K., 2003. Distributionof oxygen and hydrogen isotopes inshallow groundwaters from southernIndia: influence of a dual monsoon system.J. Hydrol., 271 (1-4), 226-239.

Dey, A. and Bhowmick, A.N., 2002.Ground water protection strategy inGhaziabad urban area, Uttar Pradesh - acase study. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 535-548.

Dineshan, V.P., Hameed, A.S., Vasu, K.and James, E.J., 2002. Application ofisotope techniques for ground waterinvestigations in the Kolar semi-aridregion. In: Proc. Intl. Conf. on Hydrologyand watershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 193-199.

Durbude, D.G., Varadrajan, N. andPurandara, B.K., 2002. Mapping of groundwater quality parameters in GISenvironment. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 568-577.

Goel, M.K., Jain, S.K. and Agarwal, P.K.,2002. Assessment of sediment depositionrate in Bargi Reservoir using digital imageprocessing. Hydrol. Sci. J., 47(5), 581-592.

Govil, P.K., Krishna, A.K. andGnaneswara Rao, T., 2002. Environmentalgeochemical studies to find out thecontamination of water in Patancheruindustrial area, Andhra Pradesh, India. In:Proc. of the IGC 2002, Dindigul, TamilNadu, (Eds. M. Thangarajan, S.N. Rai,V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 229-238.

Govil, P.K., Reddy, G.L.N. and Krishna,A.K., 2001. Contamination of soil due toheavy metals in the Patancheru industrialdevelopment area, Andhra Pradesh, India,

Environmental Geology;, 41(3/4), 461-469.

Gurunadha Rao, V.V.S., 2002. Impact ofwaste disposal practices on groundwaterresources in watersheds aroundHyderabad. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 330-335.

Gurunadha Rao, V.V.S., Dhar, R.L.,Jayachand, T. and Khoker, C.S., 2000.Mass transport modeling for assessment ofgroundwater contamination aroundMathura oil refinery, Mathura, U.P., India,Environmental Geol., 39(10), 1138-1146.

Hayagreeva Rao, K.V. and Sekhar, M.,2002. A numerical model for simulatingtransport and geochemistry ingroundwater. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 443-452.

Hegde, S.N., Puranik, S.C. and Sarwade,D.V., 2002. Evaluation of ground waterquality in dug and borewells of sub-urbanareas of hubli, Dharwad MunicipalCorporation Area, Karnataka, India. In:Proc. Intl. Conf. on Hydrology andwatershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 619-628.

Hodlur, G.K., Deshmukh, S.D., Rao, T.V.and Dhakate, R., 2002. Hybridisation ofqualitative and quantitative resistivity datainterpretation - a technique to resolve thefresh and brackish water in aquifers inregional affected terrains (a case study).In: Proc. of the IGC 2002, Dindigul, TamilNadu, (Eds. M. Thangarajan, S.N. Rai,V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 279-288.

Hodlur, G.K., Ravi Prakash, M.,Deshmukh, S.D. and Singh, V.S., 2002.Role of some salient geophysical,geochemical and hydrogeologicalparameters in the exploration of freshgroundwater in a brakish terrain.Environmental Geol., 41(9), 861-866.

Jain, C.K. and Sharma, M.K., 2001.Distribution of trace metals in Hindonriver system, India. J. Hydrol., 253, 81-90.

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Jain, C.K., 2000. Application of chemicalmass balance approach to determinenutrient loading. Hydrol. Sci. J., 45(6),572-587.

Jain, C.K., 2001. Adsorption of zinc ontobed sediments of the river Ganga:adsorption model and kinetics. Hydrol.Sci. J., 46(3), 419-434.

Jain, S.C., Singh, V.S., Rao, T.V., Rao,M.N. and Negi, B.C., 2002. Groundwaterexploration in shaley limestone terrain. In:Proc. Intl. Conf. on Hydrology andwatershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 64-71.

Jain, S.K. and Geol, M.K., 2002.Assessing the vulnerability to soil erosionof the Ukai Dam catchments using remotesensing and GIS. Hydrol. Sci. J., 47(1),21-40.

Jain, S.K., Kumar, S. and Varghese, J.,2001. Estimation of soil erosion from aHimalayan watershed using GIStechnique. Water Resources Management,15, 41-54.

Jain, S.K., Singh, P. and Seth, S.M., 2002.Assessment of sedimentation in Bhakrareservoir in the Western Himalyan regionusing remotely sensed data. Hydrol. Sci. J,47(2), 203-212.

Jayasena, H.A.H. and Abeyrathne, P.T.,2002. Application of geostatistics to thehydrochemical data from the hard rockaquifers in Sri Lanka – A case study. In:Proc. of the IGC 2002, Dindigul, TamilNadu, (Eds. M. Thangarajan, S.N. Rai,V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 289-304.

Jena, S.K. and Tiwari, K.N., 2002. Runoffestimation using Distributed CurveNumber technique. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 456-465.

Jothiprakash, V., Mohan, S. and Elango,K., 2002. Artificial recharge throughpercolation ponds. In: Proc. of the IGC2002, Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 193-198.

Kameshwari, S.B., Bhole, A.G.,Paramsivam, R., Muthal, P.L. and Pande,S.P., 1999. Arsenic removal fromgroundwater by coagulation process, J.Indian water work Assoc., XXXI(4), 231-235.

Khan, B.A., Rao, B.V. and Gurnadha Rao,V.V.S., 2002. Groundwater flowmodeling of Vattigudipadu watershed,Krishna district, A.P., India. In: Proc. Intl.Conf. on Hydrology and watershedmanagement (Eds. B. Venkateswara Raoet al.), 18-20 Dec., Hyderabad, 409-418..

Kirti Srivastava and Rai, S.N., 2002.Stochastic modeling of groundwater flowin a heterogeneous aquifer. In: Proc. ofthe IGC 2002, Dindigul, Tamil Nadu,(Eds. M. Thangarajan, S.N. Rai, V.S.Singh), IBH & Oxford Publ. Co., NewDelhi, 471-476.

Krishnaiah, C., 2002. Analysis ofcontaminant trnsport in groundwater usingfinite element method, Ph.D. Thesis, Univ.of Pune, Pune.

Krishnamurthy, G. and Pradeepkumar, M.,2002. Application of electrical resistivitymethod for quantification of weatheredlayer thickness and tracing of pollution intannery belt in and around Dindigul, TamilNadu. In: Proc. of the IGC 2002, Dindigul,Tamil Nadu, (Eds. M. Thangarajan, S.N.Rai, V.S. Singh), IBH & Oxford Publ. Co.,New Delhi, 27-34.

Krishnamurthy, N.S., Dewashish Kumar,Negi, B.C., Jain, S.C. and Shakeel Ahmed,2002. Resistivity investigations foridentifying fractured aquifers in a graniticterrain. In: Proc. Intl. Conf. on Hydrologyand watershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 103-110.

Kumar, A. and Prasad L.B., 2002.Development of spatial decision supportsystem for ground water using GIS basednumerical modeling technique- MargajoWatershed, Hazaribagh. In: Proc. Intl.Conf. on Hydrology and watershedmanagement (Eds. B. Venkateswara Raoet al.), 18-20 Dec., Hyderabad, 474-485.

Kumar, D., Ahmed, S., Prakash, B.A., andKrishnamurthy , N.S., 2002. Combined

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use of geological logs and verticalelectrical soundings for spatial predictionof layer thickness and depth to bed rock inan aquifer. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 383-390.

Kumar, D., Krishnamurthy, N.S., Ahmed,S., Jain, S.C. and Dhar, R.L., 2003. Mise-a-la-masse Technique in establishing thelateral fractures in hard rocks. J. Geol.Soc. India, 61(2), 185-194.

Kumar, K., Miral, M.S., Joshi, V. andPanda, Y.S., 2002. Discharge andsuspended sediment in the meltwater ofGangotri Glacier, Garhwal Himalaya,India, Hydrol. Sci., J., 47(4), 611-620.

Kumar, M.S. and Elango, L., 2002.Rainfall and groundwater levelrelationship in a part of the lower Palarbasin, Tamil Nadu, India. In: Proc. of theIGC 2002, Dindigul, Tamil Nadu, (Eds.M. Thangarajan, S.N. Rai, V.S. Singh),IBH & Oxford Publ. Co., New Delhi, IBH& Oxford Publ. Co., New Delhi, 417-422.

Kumar, V. and Singh, O., 2002.Modelling of Spatial Variability ofGroundwater Quality in Jammu district(J&K). In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), 339-350.

Kundu, N., Panigrahi, M.K., Tripathi, S.,Munshi, S., Powell, M.A. and Hart, B.R.,2001. Geochemical apprisal of fluoridecontamination of groundwater in theNayagarh district of Orissa, India.Environmental Geol., 41(3/4), 451-460.

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Venkatesh, B. and Chandramohan, T.,2002. Regional flood frequency analysisusing L-moments. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 440-446.

Venkateswara Rao, B. and Kareem Khan,P., 2002. Development of softwarepackage for evaluation of groundwaterpotential in hard rock areas. In: Proc. ofthe IGC 2002, Dindigul, Tamil Nadu,(Eds. M. Thangarajan, S.N. Rai, V.S.Singh), IBH & Oxford Publ. Co., NewDelhi, 485-496.

Venkateswara Rao, B. and Ramadurgaiah,D., 2002. Comparative study of resistivitysoundings and lithologs in a Khondaliticterrain in an area around Vizianagaram,A.P., India. In: Proc. Intl. Conf. onHydrology and watershed management(Eds. B. Venkateswara Rao et al.), 18-20Dec., Hyderabad, 132-143.

Venkateswara Rao, T., 2002. Structurallydisturbed terrain delineated by electricalresistivity method for groundwaterexploration. In: Proc. of the IGC 2002,Dindigul, Tamil Nadu, (Eds. M.Thangarajan, S.N. Rai, V.S. Singh), IBH& Oxford Publ. Co., New Delhi, 85-90.

Vishwanadh,G.K. and Sanjeeva, G., 2002.Rainfall prediction through auto regressivemodel. In: Proc. Intl. Conf. on Hydrologyand watershed management (Eds. B.Venkateswara Rao et al.), 18-20 Dec.,Hyderabad, 447-458.

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METEROLOGY AND ATMOSPHERIC PHYSICS

V. ThapliyalIndia Meteorological Department, Pune – 411 005

Introduction

This report gives an outline of the workdone by the scientific organizations ofIndia in the field of Meteorology andAtmospheric Physics during the period1998- 2002. In this field more than 30organizations including Universities,Institutes, other Government agencies areinvolved in research, capacity building,observational and data base developmentwork etc. In this report, the work doneduring 1998-2002 is broadly summarisedunder the following headings:

1. Monsoon studies2. Atmospheric modelling and

Dynamics3. Climate studies4. Air-sea Interaction5. Atmospheric Physics,

Chemistry, Cloud andRadiation

6. Atmospheric Boundary layer7. Satellite Meteorology8. Experimental studies.

Inputs were requested from over 30organizations. A selected list oforganizations those who have contributedto this report within the requested timeframe are given in the report. A selectedbibliography of papers, supplied by thecontributing organizations as well ascollected from the literature is also givenat the end of the report.

Monsoon studies

Impact of monsoon dominates in manyspheres of national activities including thesocio- economic sector. In view of this,the study of monsoon remained to be themajor area of research in India. Variousaspects of monsoon and its systems,including their interactions, inter-annualand intra-seasonal variability, globalteleconnections, prediction on variousscales, numerical impact assessment and

diagnostic studies- were given greatimportance. Herein after the wordmonsoon is used for Southwest Monsoon.Major research programmes forunderstanding the variability of monsoon,the oceans and the coupling of ocean andatmosphere were also carried out. Someof the results of such major programmeslike INDOEX (Indian Ocean Experiment),BOBMEX (Bay of Bengal MonsoonExperiment), and ARMEX (Arabian SeaMonsoon Experiment) are summarised insection (8) under Experimental studies.

Studies on advance phase of monsoonshowed that the establishment of mid-tropospheric subtropical ridge over northIndia and Tibetan plateau after mid Junewas found to be a key factor inmaintaining monsoon trough over thecountry. The warming of Tibetan plateauby the middle of June was found to beconducive for the establishment of Tibetananticyclone and advance of southwestmonsoon. In its absence, the westerlytrough propagated equatorwards andhindered the progress of monsoon.

The north Indian Ocean becomes thewarmest area of the world oceans prior tothe onset of southwest monsoon in June.During this period, a zonal band of highsea surface temperature (SST), the"thermal equator" (TE), moves over thisregion concurrently with the IntertropicalConvergence Zone (ITCZ). Using aweekly SST data set, it was shown thatanother SST high developed off southwestIndia in the Lakshadweep Sea in March,well before the TE moved in to the area,and that it continued to retain its identityuntil the onset of monsoon. By, May,when the thermal equator and ITCZmoved over the region, the high could beseen embedded in the TE. It wasspeculated that, at this time the highhelped in producing conditions that wereconducive for the genesis of the monsoononset vortex.

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Study of rocket wind data over Thumba(India) and upper wind data in the lowerstratosphere over Singapore, behaviour ofequatorial stratospheric and mesosphericzonal winds in governing monsoon rainfallover India indicated that the westerlywinds/light- easterly winds during phasesof QBO in preceding January and Maywere favourable for good monsoon whileeasterlies were non conducive for goodmonsoon. The inverse relationship of SSTAnomaly over Nino 3 area and Indianseasonal monsoon rainfall was found to besignificantly enhanced during the easterlyphase of QBO. This probably explainswhy every EL Nino is not associated withthe drought over India.

The Indian monsoon rainfall (IMR)showed epochal behaviour with theperiods 1895-1930 and 1963-1990characterised by below normal rainfallwith high frequency of droughts while theperiods 1871-1895 and 1930-1963characterised by above normal rainfallwith very few droughts. It was seen thatthe impact of El Nino was more severeduring the below normal epochs than theabove normal epochs. Further analysisrevealed that probably IMR is tendingtowards an epoch of above normal rainfallwith a turning point around 1990. Thismay be another possible reason for Indianot experiencing a drought during the1991-94 and 1997 El Nino episodes.

Analysis of the 140-year historical recordsuggested that the inverse relationshipbetween El Nino - Southern Oscillation(ENSO) and the Indian monsoon brokedown in recent decades. Two possiblereasons emerged from the analyses. Asouth- eastward shift in the Walkercirculation anomalies associated withENSO events could have resulted inreduced subsidence over the Indian region,thus favouring normal monsoonconditions. Additionally, increased surfacetemperatures over Eurasia in winter andspring, which were a part of the mid-latitude continental warming trend, mighthave favoured the enhanced land-oceanthermal gradient conducive to a strongmonsoon. These observations raise the

possibility that the Eurasian warming inrecent decades could help to sustain themonsoon rainfall at a normal level despitestrong ENSO events.

Rain over northern parts of India andposition of 500 hPa ridge in the month ofApril showed significant correlation withsubsequent SST anomalies of easternPacific Ocean (Nino-3 region). As therelationship was stronger during El-Ninoyears, it could be used for prediction ofpeak warming which usually occursduring October to December months.

In the light of the global warmingscenario, the inter-annual and decadalvariability of the IMR was examined byusing observed data for the period 1871-2001. There was no clear evidence tosuggest that the variability of the IMR wasaffected by the global warming.Connections between the ENSOphenomenon, Northern Hemispheretemperature, and Eurasian snow coverrevealed that the correlations were weakand changed signs in the 1990s suggestingthat IMR was de-linked not only with thePacific but the Eurasian continent also.The fact that NH temperature / snowrelationships with IMR were weaksuggested that the global warming couldnot be a cause for the recent ENSO-Monsoon weakening. The analysis ofNortheast monsoon rainfall data for theperiod 1901-1997 revealed that ENSOyears were generally associated withenhanced northeast monsoon precipitation.

Century-long observations providedevidence for an interesting out-of-phasevariability between the first principalcomponent of Baiu rainfall over theJapanese archipelago and the monsoonrainfall over India during the earlysummer season (June and July). It wassuggested that the circulation near thesubtropical region of the west PacificOcean tended to vary in-phase with thatover the Indian subcontinent, so that anintensified (weakened) west Pacificsubtropical high was accompanied by anintensified (weakened) Baiu circulationover Japan and a weakened (intensified)monsoon circulation over India. A pattern

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consisting of an anomalous low over theCaspian and Aral Sea regions, a high overMongolia and an anomalous low overKorea and Japan, tended to be associatedwith increased Baiu rainfall over Japanand decreased monsoon rainfall overIndia.

Studies focused on the Eurasian sectorsnow depth revealed that there werelocalized regions over Russian sector,where the snow depth variations duringJanuary had a substantial impact on thesubsequent IMR. One of the importantfindings of this study was that the coherentareas of significant relationship shiftedsouthward as time progressed from winterto spring and non-El Nino related droughtsover India were associated with snowdepth variations over the above localizedregions.

Studies on the energetics of monsoon forits various stages were carried out.Analysis of monthly momentum transportof zonal waves at 850 hPa between 30°Sand 30oN for January to April showed apositive correlation between IMR and themomentum transport of wave zero overlatitudinal belt between 25°S and 5°Nduring March. Northward (Southward)momentum transport of wave zeroobserved in March over the beltsubsequently led to a good (drought)monsoon season over India which wasfound to be true even when the year wasmarked with El Nino event.

In order to understand the intra-seasonaland inter-annual variability of themonsoon circulation, global energeticsduring the early monsoon months wereexamined. Computations showed that themaximum amount of kinetic energy (KE)was clustered around 250 hPa level in theatmospheric region between 1000–100hPa. The maximum fluctuations in the KEwere also observed at 250 hPa level duringthe period of the study. The 1st peak of KEwas seen to occur during 1st week of June,which was just after the onset of monsoonover India and neighbourhood. The 2nd

peak was observed after a period of about45 days. This probably reflected the 40-60days oscillation.

Temporal variation of kinetic energy ofwave number 1 showed a steep decreasep r io r t o t he fo rma t ion o fdepressions/cyclonic storms in the Bay ofBengal. The kinetic energy of wavenumber 1 weakened (strengthened) whenthe depression/cyclonic storm in the Bayof Bengal strengthened (weakened). Afterthe decay of the cyclonic system, wavenumber 1 received the kinetic energy. Thestudy suggested a signal about theformation of the depression / cyclonicstorm in the Bay of Bengal.

A diagnostic mathematical model wasused to understand the dynamics of lowfrequency intra-seasonal oscillationsduring the contrasting monsoon years at850 hPa and 200 hPa. Latitude-frequencydistributions of nonlinear energyinteractions over Indian region and globaltropics at 850 hpa showed strong energytransfer to low frequency oscillations onMadden- Julian time scale to the north ofthe Equator up to 20°N. Strong non-lineartriad energy interactions among large scalemonsoon circulations, low frequencytransients on Madden Julian time scale andseasonal mean flows were found to beviable dynamical mechanism for goodsummer monsoon over Indian region andglobal tropics.

North Atlantic Oscillation (NAO) andSouthern Oscillation (SO) were found tobe inverse oscillations and just before thebeginning of monsoon season, therelationship between them was found tochange sharply. The behaviour of thesetwo oscillations was in phase in the excessmonsoon years while it was out of phasein the deficient monsoon years.Simultaneous impact of NAO and SO onmonsoon activity over Indian sub-continent was expressed as an index calledeffective strength index (ESI) and wasdefined on the basis of monthly NAO andSO indices. ESI in the month of Aprilshowed an inverse association with Indiansummer monsoon rainfall . Therelationship was statistically significant. Itwas also seen that during the positivephase of ESI the easterly over the centralequatorial Pacific Ocean intensified anddue to which there was a shift in the

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Walker circulation towards the Indiansubcontinent. This ultimately increased theconvergence over Indian region, which ledto higher monsoon rainfall activity.

The analysis of the duration of breaks inthe month of July and August, with NorthAtlantic Oscillation (NAO) indicesindicated that during the negative phase ofNAO there was either less duration ofbreaks or no breaks in the monsoonactivity while during positive phase ofNAO the break monsoon conditionprevailed significantly. The study helps tounderstand the dynamical aspect of breaksin monsoon condition over Indian regionand also the tropical- extra tropicalinteractions.

The inter-annual variations of SSTs in theIndian Ocean (IO-SST) in summer andautumn appeared to have some connectionwith winter circulation anomalies over theEurasian region during the period,resulting in warmer than normal surfacetemperature conditions in the recentdecades. Keeping in view the fact that thesurface temperatures over Eurasia inwinter and spring played a dominant rolein determining the strength of themonsoon over India, the enhancedEurasian temperatures in recent decades,both as part of the general global warmingand through IO-SST induced mid-latitudecirculation response, might be a plausiblemechanism for the recent long-leadcorrelations between IO-SSTs and IMR.May wind stresses over Arabian Sea werealso found to be statistically significantlyrelated with ensuing IMR.

Decadal scale variability in Indianmonsoon rainfall seems to be forced byglobal scale SST anomalies. The analysisof SST Index (Southern Hemisphereminus Northern Hemisphere oceantemperature anomalies) for the monthsJuly to September showed that the twoperiods 1901 to 1920 and 1965 to 1990, inwhich India witnessed frequent droughtsbroadly corresponded with warm SSTindex.

Studies, addressing the Indian summermonsoon teleconnections and long range

forecasting of Indian summer monsoon,identified new teleconnections of IMRwith global surface air temperatures,Indian Ocean sea surface temperatures,winter surface pressure over Eurasia andSea Surface Temperature (SST), Outgoing Long-wave Radiation (OLR) overAtlantic Ocean. Some of theseteleconnections are being used aspredictors in the operational Long RangeForecast (LRF) model of IndiaMeteorological Department. Models forlong range forecasting of All Indiasummer monsoon rainfall and broadhomogeneous regions rainfall using newtechniques like artificial neural network,principal component, discriminant andPower Transfer analysis have also beendeveloped.

Spochal changes in relationship betweenvarious predictors and the All IndiaMonsoon Rainfall, which are mainlyresponsible for long range, forecast errors,as in 2002, were analysed in detail. Totackle this problem at least partially,prediction by time series using anArtificial Neural Network (ANN)technique with error-back propagationalgorithm was attempted. Though resultsfor IMR forecast appeared to besatisfactory, but for monthly scales theywere very poor. To tackle the problem ofchanging relationship, a new techniquewas developed to analyze the spochalchanges of predictor-IMR relationship.Based on this technique a hypothesis wasproposed which states that the resultantassociation between a predictor andmonsoon rainfall can be expressed as asum of basic climatic (long period)association and perturbed climatic (veryshort period) association and if both ofthese associations between the predictorand predict and are used, the accuracy ofthe forecast would be greater than thatcould be achieved with the existing longrange forecast models. The hypothesiswas validated by formulating a newmodel, termed as Power Transfer Model.

Atmospheric Modelling and Dynamics.

Modeling of atmospheric and oceanicprocesses, and their interactions remained

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another thrust area of research. Simulationand sensitivity studies helped in the betterunderstanding of atmospheric phenomenaand circulation. Studies were carried out toincorpora te d i f fe ren t phys ica lpa ramete r i sa t ion schemes andinitialization schemes in models of variousscales.

Utilizing radiosonde and M-100 rocket-sonde data, collected over Thumba (8°N)in the 20-80 km altitude region for theperiod 1971-1993, a multifunctionalregression model was developed to studythe long-term temperature trends in themiddle atmosphere vis-à-vis possibleglobal change. Results of the studyindicated an annual negative temperaturetrend of 1 to 2.5° K/decade from 20 to 45km, 2 to 3°K/decade in the lowermesosphere and a higher cooling up to5°K/decade in the upper mesosphere.

A pure baroclinic 16- layer quasi-geostrophic numerical model was appliedto determine the baroclinic structure of asevere cyclonic storm that formed duringJune 1994. It was found that the baroclinicstructure of preferred wavelength wascomparable to that of the observedstructure of the cyclonic storm. Byinclusion of surface friction, theperturbation field was slightly enhancedbut the vertical extension remainedunchanged. The model was found usefulin understanding the occurrence oftransient disturbances, which led to theonset of South West monsoon.

Results obtained from a set of atmosphericgeneral circulation model (AGCM)experiments indicated that the IndianOcean SSTs generally had much lessimpact on the monsoon variabilitycompared to the Pacific Ocean. Besides,the impact of ENSO on the Indianmonsoon was found to be much less in thepresence of strong continental warming,suggesting that the enhanced land-seagradient and an enhanced monsoon due togeneral warming could counter thenegative impacts of El Nino on themonsoon to a large extent and therebymight have weakened the connection

between these two important globalclimate phenomena.

Diagnostic analysis of observations and aseries of ensemble simulations, using anAGCM were carried out with a view toexamine the wide-spread suppression ofthe seasonal summer monsoon rainfallover the Indian subcontinent in 2000.During this period, the equatorial andsouthern tropical Indian Ocean werecharacterized by warmer than normal seasurface temperature (SST), increasedatmospheric moisture convergence andenhanced precipitation. The findings ofthis study revealed that the strengtheningof the convective activity over the regionof the southern equatorial trough played akey role in inducing anomaloussubsidence over the subcontinent andthereby weakening the monsoon Hadleycell.

A six-member ensemble AtmosphericGeneral Circulation Model (AGCM) runs,made with observed global SSTs wereanalysed to examine the model's ability tosimulate various global climatic featuressuch as the Indian summer monsoon,North Atlantic Oscillation (NAO) etc. andtheir inter-annual variability. The resultswere also utilized to study thepredictability aspects of various globalmeteorological variables such as theprecipitation, surface temperature, sealevel pressure etc.

Climate Studies

Climate has far reaching consequences onlong- term socio- economic environmentand sustainable developments. The rolesof trends, periodicities, variabilities ofclimate and those parameters related toclimate change have a very importantplace in the current research activities.Analysis of various factors that affectclimate and the simulation studies areengaging the attention of many scientists.

A project, Climate Related EnvironmentMonitoring (CREM), which aims atestablishing a network of stations in Indiato generate primary data on green housegases and aerosols on a long-term basis

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was under taken. Such data are of vitalinterest to our country with regard toclimate change studies and to create asound database, which can be used infuture climate change negotiations in theUnited Nations framework and also forunderstanding different aspects of climatechange.

Climate variations and teleconnectionsover South and East Asia wereinvestigated by using monsoon rainfalldata for a period of 1881-1998 over India,Mongolia, China, Korea and Japan. Theinterconnections between the monsoon-related events (rainfall over South Asia,rainfall over East Asia, northernhemisphere circulation, tropical Pacificcirculation) appeared to strengthen (orweaken) around the same time, implyingthat monsoon-related events overgeographically separated regions gotlinked (or delinked) around the same time.

Simulation of climate using a simplediagnostic model, based on moisture andenergy budget, which could demonstratethe seasonal variation of monsoon rainfallwith the seasonal variations ofevaporation, net radiation at the top of theatmosphere and precipitable water vapourengaged the attention of scientists. Resultsthrew some light on the difficulty insimulating the climate.

A few epochal decreasing and increasingtrends in the frequency of cyclonicdisturbances over the Indian Seas werefound during past hundred years. Thefrequency of cyclonic disturbances in themonsoon season was also found to showthe typical epochal trends. It was observedthat the genesis potential (GP) was greaterfor developing synoptic scale disturbancesin the westerly phase than in the easterlyphase of QBO. Also, cold temperatures inthe lower stratosphere at 60°N in thewesterly phase of QBO were found to beassociated with more number of cyclonicstorms over Indian seas.

In order to reconstruct the variations in theintensity of summer monsoon precipitationduring the late Quaternary, the analyses oftwo sediment cores from the southwestern

continental margin of India was made. Itindicated that the summer monsoons ingeneral were weaker during the lateglaciation, with distinct events ofintensification of approximately 28 000and 22 000 yr BP.

Recent trends in the tropospherictemperatures were studied by usingobjectively interpolated upper air andsurface data of Indian stations on a 2° x 2°grid. The analysis of all India meanmonthly and seasonal temperature seriesindicated warming at the surface levelsand cooling at upper levels. Seasonalvariations in tropopause height andtemperature over Indian stations indicatedthat on annual and seasonal scales therewas a significant increasing trend in thetropopause height over almost all thestations south of 20°N.

Studies of trends in rainfall and radiationover smaller spatial scales over Indiaindicated that all India rainfall did notshow any trend, but showed epochaldecreasing and increasing trends. In recentyears a decreasing trend in rainfall wasnoticed over most of the hilly areas. Mostof the stations did not show any trend inglobal radiation. However, a slightincreasing trend of tropospheric ozone anda decreasing trend in stratospheric ozonewere observed.

In recent decades an increasing trend inthe number of poor visibility days (lessthan 2000 metres) in winter season,particularly in morning hours was noted.One of the reasons could be thedegradation of air quality due tosignificant increase in anthropogenicpollutants in the urban areas. On seasonaland annual scale, a decreasing trend inheavy rainfall events was noted over mostof the stations of the country in recentyears.

Air Sea Interaction

The large-scale atmospheric circulation isgreatly influenced by the oceaninteractions. The location and intensity ofthe convection and diabetic heating of theatmosphere are greatly influenced by

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ocean parameters like SST. An importantquestion in the tropical dynamics is theexact role of SST in the genesis of theobserved spectrum of oscillations. SST, asthe major lower boundary forcing withsubstantial variability at different scales, isknown to be important for the atmosphericprocesses like onset and maintenance ofconvection. However, its role in range andquality of atmospheric simulation needs tobe quantified at various scales. Inparticular, it is not clear how the higherfrequency variability of SST affects thea tmospher ic processes . Recentobservations and theoretical studiesemphasised intra-seasonal variability ofSST with significant amplitudes. It isexpected that these SST intra-seasonaloscillations will have significant effect onthe simulated atmospheric systems.

Simulation of two contrasting monsoonyears by a GCM indicated very significantinfluence of temporal structure of SST onprecipitation. Contrary to the generalbelief, it was found that use of daily SSTcould substantially influence and improvethe monsoon simulation. This in turnemphasized the need for quality forecastsof the SST field and in particular, need forreliable ocean-atmosphere coupledmodels.

A parameterization of ocean atmospherecoupling in the tropics was developedusing the concept of convective relaxationtime scale, known as convective oceanatmosphere coupling. It was found that thesea surface temperature affected the lowlevel atmospheric circulation onlyindirectly, by modulating the columnmoisture and hence the columnprecipitation. Since precipitation was athreshold process, the convective ocean-atmosphere coupling also became asecond order threshold process. Theseworks showed that such a formulation ofocean atmosphere coupling, in addition tobeing conceptually appealing, couldexplain the genesis of a broad spectrum ofatmospheric and oceanic variabilities.Both moist feedbacks and the basingeometry played crucial roles inunderstanding and modeling the lowfrequency variabilities over the Indian

Ocean region.

An examination of the trend in SST andtotal cloud amount over the Indian Oceanfor the period 1951 to 1998 showed thatthe cloud cover over Bay of Bengal wasmodulated by the ENSO events. On interdecadal scale, the amount of low cloudsignificantly increased after 1980 whichmight be associated with thecorresponding inter decadal changes ofSST over north Indian Ocean that wereobserved during late 1970s.

The air-sea interaction processes over thetropical Indian Ocean region are studiedusing sea surface temperature data fromthe Advanced Very High ResolutionRadiometer sensor onboard the NOAAseries of satellites. The analysis ofcolumnar water-vapour content, low-levelatmospheric humidity, precipitation, windspeed, and back radiation obtained fromthe Special Sensor Microwave Imager onboard the U.S. Defense MeteorologicalSatellite Program for two contrastingmonsoon years, 1987 (deficit rainfall) and1988 (excess rainfall) indicated that theevaporation rate over the south IndianOcean and the low-level cross-equatorialmoisture flux seemed to have exertedconsiderable influence on the ensuingmonsoon activity over India while theevaporation over the Arabian Sea exerteda little influence.

An analysis of the heat budgets of thenear-surface Arabian Sea and Bay ofBengal showed significant differencesbetween them during the monsoon. In theArabian Sea the winds associated with themonsoon were stronger compared to Bayof Bengal and favoured the transfer of heatto deeper layers owing to overturning andturbulent mixing. As a result, the seasurface temperature in the bay remainedhigher than 28 °C, thereby supportinglarge-scale deep convection in theatmosphere during the monsoon.

Atmospheric Physics and Chemistry,Cloud and Radiation

In the light of anthropogenic impact onclimate, research in the field of

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atmospheric Physics, Chemistry andradiation remained another thrust areaamongst Indian Scientists. Effects of theincreased emission of green house gases,stratospheric ozone depletion, occurrenceof acid rain, reduction in visibility due tosmog formation, the changingcharacteristics of troposheric andstratospheric aerosol, cloud physics,electricity and weather modification weregiven great importance. On these aspects,a good number of observational as well asmodelling studies were carried out.

To monitor the characteristics of uppertropospheric and stratospheric aerosolincluding the influence of winds andatmospheric stable layers such astropopause on aerosol characteristics,experiments were carried out using Nd:YAG lidar system, available at NationalMesosphere-Stratosphere-TroposphereRadar Facility. Simultaneous observationsof atmospheric stable layers and 3-Dimensional vector winds also werecarried out using MST radar. The resultshelped in understanding radiativeproperties of cirrus clouds and theirinfluence on tropopause therebystratosphere - troposphere interaction. Ananalysis of Argon-ion lidar andpolarization lidar data indicated that thelidar has the capability to capture themulti-layer cloud structures, interfacebetween cloud condensation nuclei in thesub-cloud layer and in the vicinity ofcloud-base and anisotropy of aerosolscattering.

The analysis of multi-filter solarradiometric observations of aerosols andtrace gases indicated significant inter-annual variability of columnar aerosoloptical depth, aerosol size distribution,ozone and precipitable water content. Allthe parameters were found to show adecreasing trend with varying magnitude.

An analysis of tropical troposphericcolumn ozone (TCO) data, derived byNimbus7 and Earth Probe -total ozonemapping spectrometer (TOMS) during theperiod 1979-2002 over the tropics (12.5°Sto 12.5°N), revealed statisticallysignificant linear trends widely believed to

be of anthropogenic origin. An increase inTCO by 23 (± 10) % in the past twodecades was found. That means a radiativeforcing of climate might be up by about0.3Wm-2. If sustained, it could haveserious climatic implications.

A two- dimensional interactive model ofradiation, dynamics and chemistry wasused to reconstruct the annual verticaldistribution of thermal structure and tracegas concentrations of the lower and middleatmosphere for the period extending fromlast ice age to the present, with ice core airdata of the forcing parameters like CO2,CH4 and N2O as input. Model resultsshowed that the considerable reduction inthe greenhouse gas content for the last iceage resulted in cooling of troposphere anda warming by about 10°K to 15°K in theupper stratosphere as compared to present.The variation in temperature was foundclosely related with the water vapourcontent. The percentage change in ozoneconcentration for the last glacial periodwas to a maximum of 50% near the polesin the upper stratosphere and about 10% inthe tropics.

Studies were undertaken, using thecoupled neutral-ion photochemical modelto demonstrate that gas-phase sulfurchemistry played a vital role inperturbations of the stratospheric ioncomposition following the Pinatuboeruption. Model calculations indicated thatimmediately after the eruption, the largeamount of SO2 injected directly into thetropical stratosphere produced additionalsulfuric acid vapour, which increased theabundance of heavy negative ion familyby several orders of magnitude over theambient. The perturbation (now weaker) inion composition continued to be unabatedeven after one year of eruption but settleddown to background level after 2 years.

Data on atmospheric electric field andelectric conductivity, obtained at Maitriduring XVI Indian Scientific Expedition toAntarctica showed a peak in electric fieldat 1300 hrs and a secondary peak inelectric field at 1900 hrs. The electricalconductivity did not show any significant

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variation during the period ofmeasurement at Maitri, Antarctica.

Aerosol size distribution obtained duringthe onward and return journeys of the XVIexpedition to the Antarctica showed largeaerosol concentrations and their north tosouth positive gradient over northernIndian Ocean. The results also indicatedthe transport of air pollutants fromnorthern to Southern Hemisphere withcross-equatorial flow. Some pockets ofvery high aerosol concentrations wereobserved in and around the Inter TropicalConvergence Zone. Some peaks inaerosol concentration associated with thelow-pressure systems were observedaround the continent of Antarctica. Theseobservations strongly demonstrated theeffect of wind direction on the land-to-ocean transport of the atmosphericaerosols. The total aerosol concentrationswere normally observed between 800 and1200 partciles/cm3 at the coastal stations atAntarctica in summer. Aerosol sizedistributions were found to be generallytri-modal and a pen-ended with a peakbetween 75 and 133 nm and two minimaat 42 and 420 nm size distributionsremained almost similar for several hoursor even days in the absence ofmeteorological disturbances.

The atmospheric electric conductivity wasmeasured over the Indian Ocean ondifferent cruises of Ocean Research VesselSagar Kanya during the Indian OceanExperiment. Results showed a north-to-south positive gradient of conductivityextending up to the Inter TropicalConvergence Zone in the SouthernHemisphere. Special observations ofmaritime aerosols, total column ozone andprecipitable water content using multi-band solar radiometers were carried outonboard ORV Sagar Kanya over Bay ofBengal as part of the Bay of BengalMonsoon Experiment-99. The resultsindicated interestingly lower aerosoloptical depths and size distributions withabundance of coarse-mode particles ascompared to those aerosols of typical landorigin which depicted day-to-day variationin aerosol optical depth at differentwavelength of the radiometer. When a

low-pressure area was present, greatoptical depth near the coast and suddenfall in optical depth during 13-19 August1999 due to cloud scavenging andassociated rainfall were also noted.

To study the effect of vertical electric fieldon the rate of evaporation of water drops,a laboratory experiment was conducted bysuspending drops in vertical wind tunnelunder vertical electric field. The resultshowed that the rate of evaporation ofcharged drops was found to be slower thanthat of uncharged drops. Also at the cloudbase, a charged drop is required to besmaller in size as compared to anuncharged drop in order to reach theEarth’s surface with the same size. Thedistortion of water drops suspended in asmall vertical wind tunnel was also studiedby taking their photographs with a 16-mmmovie camera. Results showed that thedeformation of the drop increases with thesize of the drop and also with the increasein the horizontal electric field.

Studies using International Satellite CloudClimatology (ISCCP) and Earth RadiationBudget Experiment (ERBE) data showedthat among deep convective regions of thetropics, only in the Asian monsoon region,the net cloud radiative forcing was largenegative, exceeding 30 Wm-2 during themonsoon season. The combination ofpresence of large amount of high cloudsand high optical depth of these clouds wasattributed to it.

Anthropogenic emissions over the Asianregion have been growing rapidly with thei n c r e a s e i n p o p u l a t i o n a n dindustrialization. This probably led to abrownish haze over most of the NorthIndian Ocean and South Asia duringwinter and spring. The haze is known toreduce the surface solar insolation byabout 10% (-15 W/m2) and nearly doublethe lower atmospheric solar heating. Tostudy the effects of absorbing aerosolswith competing radiative forcing on theatmosphere and the surface, an analysis ofobserved surface-temperature variationsover the Indian subcontinent was carriedout. The analysis revealed that theabsorbing aerosols led to a statistically

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significant cooling of about 0.3°C since1970s.

Under the Arabian Sea MonsoonExperiment Phase-I, cruise observationswere undertaken on board ORV SagarKanya. Surface ozone was monitored withthe help of UV photometric ozoneanalyser at 254 nm wavelengths. Hourlyanalysis showed no prominent diurnalvariation of surface O3 over the ocean.Mass size distribution of aerosols showeda bimodal distribution with a small peak infine size (0.65 mm) and a major peak incoarse (4.7 mm) indicating a dominance ofcoarse size sea-salt particles and lessanthropogenic influence over the sea.

Nitrous oxide (N2O) is an importantgreenhouse gas that plays a crucial role inthe stratospheric ozone and thereby in theradiation budget. Analysis of seasonal andannual N2O concentration fields for theArabian Sea surface layer using a databasecontaining more than 2400 valuesmeasured between December 1977 andJuly 1997 showed that N2O concentrationswere highest during the southwest (SW)monsoon along the southern Indiancontinental shelf. It was seen that annualemissions range from 0.33 to 0.70 Tg N2Owas dominated by fluxes from coastalregions during the SW and northeastmonsoons. Arabian sea is an important siteof bio-geo-chemical ocean- atmospheretransfers and plays a crucial role inregulating the atmospheric chemicalcomposition and the climate. Due to adelicate bio-geo-chemical balance, theArabian Sea is expected to be among thefirst to react to potential anthropogenicperturbations.

A general increase of turbidity at allGlobal Atmospheric Watch (GAW)stations in India except Kodaikanal wasobserved in recent years. These stationsalso showed anomalously high values ofatmospheric turbidity in 1982-83 and1991-92 following the eruptions ofvolcanoes El-Chichon, Mexico, in April1982 and Mt. Pinatubo, Philippines, inJune 1991. The increase in atmosphericturbidity values following these eruptionswas discernible for 1.5-2 years after the

eruption. pH values from Indian stationswere around 7.0 or even higher up to1980. But by 1990 large number of pHvalues ranged between 5.0 and 6.0,indicating a severe negative change. Thiscan be attributed not only to increasingsulfate concentration but also even moreto increasing nitrate concentration.Studies addressing the climatic effects ofanthropogenic aerosol highlighted the roleof sulphate aerosols in modulating theradiation budget and thus cooling ofsurface temperatures also.

The precipitation chemistry data showedthat local effects seem to be moreimportant for chemical wet depositionthan large- scale geographical influences.Comparison of pH and other wetdeposition data showed that India is muchbetter compared to many other countriesas far as acid rain situation is concerned.

Estimation and prediction of the groundlevel concentration of the air born effluentthat might be discharged under normaloperating conditions of the nuclear powerplant or under a hypothetical accidentalcondition is a challenging task. As ithappens, most of the nuclear power plantsare located at coastal or hilly terrainwhere the meteorological conditioninfluencing the air pollution dispersion isnon-homogeneous and non -stationary.The sea – land breeze circulation anddevelopment of internal boundary layergreatly influence the trajectory anddiffusion of the pollutants at a coastal site.The terrain undulations, mountain – valleycirculation and the varying land coverinfluence the dispersion under amountainous terrain. Some of theseaspects were also investigated during theperiod. Field experiments and modelingstudies were conducted in meso and long -range atmospheric dispersion. The datacollected routinely and under fieldexperiments were found useful forstudying land, atmospheric and coastalprocesses during different seasons. Themodeling study can be used for thedevelopment of a generic numerical codefor emergency impact assessment for anynuclear/ non -nuclear effluent releases.

90

Atmospheric Boundary Layer

The exchange of mass, momentum, heatand water vapour from the earth’s surfaceto the air above is important and is takingplace through the lowest layer of theatmosphere, known as AtmosphericBoundary l aye r (ABL) . Thethermodynamic structure of the marineboundary layer over Bay of Bengal wasstudied using Radiosonde measurementsmade during the Phase II of theBOBMEX-99. The observational area wasdivided in to region I (87°-85° E), regionII (85°- 82° E) and region III (82°-80° E)depending upon the surface pressuredistribution and total cloud amount. Theresults of the analysis of the radiosondedata showed relatively dry air near theocean surface between 1000 to 950 hPaand persistent low cloud layers between900 and 700 hPa. The lifting condensationlevels of the region I were above 963 hPawhereas they were below 963 hPa overregion II and III.

Aerological observations collected oversix coastal stations when a low-pressurearea was observed during Bay of BengalMonsoon Experiment-99 were analysed.The stations in the vicinity of the systemwere found to be associated with moreconvective instability in the lower layers,less mixed layer heights and ConvectiveBoundary Layer tops reaching up to higherlevels as compared to stations away fromthe system.

A number of studies related toatmospheric boundary layer, convectionand precipitation, winds, waves andturbulence, cirrus cloud, tropopause usingthe Mesosphere-Stratosphere-Troposphere(MST) radar, Lower Atmospheric WindProfiler (LAWP), Rayleigh/ Mie Lidar,Optical Rain Gauge (ORG), Disdrometer,automatic weather station (AWS), radio-sonde /GPS-sonde and rocket borneexperiments were carried out. Duringmonsoon and post monsoon seasonsstrong turbulence was observed at theheight range of 16-20 km and a minimumin the height range of 12-16 km. Thisstrong turbulence was noted to be closelyassociated with vertical shear of

horizontal winds that were observed tooccur at the upper edge of the TropicalEasterly Jet winds.

Satellite Meteorology

For monitoring weather systems over landand ocean, like tropical cyclones,monsoon depress ions , wes te rndisturbances etc., satellites act as effectiveobserving platform. The availability ofsatellite-derived data was of enormoushelp in understanding the atmosphere anddifferent weather systems. Satellites alsoplayed important role in air- seainteraction studies and in mapping ofaerosol optical depth over land regions,associated with different geographical,terrain, meteorological and environmentalconditions.

Analysis of satellite derived out- goinglong wave radiation (OLR) data over theIndian Ocean (30°N to 30°S and 40°E to100°E) showed that the OLR of tworegions appeared to be strongly relatedwith the Indian Monsoon Rainfall (IMR).One of the regions was located over theBay of Bengal during May (Index one)and the other one over the Indian Oceanduring April (Index two). The multipleregression model developed using theseindices gave encouraging results.

The sea surface winds obtained by SSM/Iby DMSP satellite of USA were comparedwith the initial winds and the modelforecast (T80 L18) winds at 1000 hPa overthe broad region of Indian summermonsoon for the onset phase of summermonsoon. Though a speed difference of 4mps in general was observed, a goodquality, dense data over data sparseoceanic regions of Indian sub-continentwas available by using the satellite datafor resolving synoptic scale weathersystems.

A useful system was developed forassimilation of humidity profiles,estimated from INSAT infrared cloudimagery and also temperature, moistureand geopotential height data derived fromNOAA satellite in the limited areaforecasting system. Cloud motion vector

91

winds derived from the majorgeostationary satellites (INSAT, GMS,METEOSAT, GOES) were subjected toquality checks and were successfully usedin 6 hourly data assimilation cycle. Theanalysis and forecast fields generatedusing ATOVS & SSM/I data werecompared with corresponding operationalarchives. Results of these studiessuggested that the SSM/I measured TotalPrecipitable Water Content was useful toestimate the moisture content not only inthe initial state of atmospheric circulationbut also in forecasts.

Experimental studies.

The analysis of the data, collected duringBOBMEX-98 pilot showed that the Bay ofBengal was comparatively warmer thanthe Arabian Sea. An abnormal high valueof SST recorded coincided with amaximum global solar radiation at thesame time on that day. During BOBMEX-99 many unknown features came to focussuch as continuous southeastshift of the eastern end of the monsoontrough into the Bay, a sudden change inthe surface circulation pattern within a daydue to a sudden change in the circulationpattern of the mid-troposphere etc. Thelarge impact of aerosols in the ArabianSea in radiative budget was demonstrated.First measurement of the aerosols overBay of Bengal was made. A large gradientof aerosol optical thickness was foundacross the inter-tropical convergence zone.Both natural and anthropogenic aerosolswere found to be important in the ArabianSea during the period April to June. Theeffect of clouds and surface reflection andsea surface winds on aerosol radiativeforcing was also demonstrated duringthese experiments.

Surface meteorological parametersacquired during field phase of the Bay ofBengal Experiment (BOBMEX-99) for thestationary periods of the ship ORV SagarKanya over Bay of Bengal were used toestimate the fluxes of sensible and latentheat and momentum at the air-seainterface. Large-scale aspects of theatmospheric conditions over Indian Sub-continent and local meteorological

parameters over Bay of Bengal werestudied. The surface and the boundarylayer fluxes of moisture, sensible heat andmomentum exhibited a large amplificationas waves in the Madden -Julian Oscillation(MJO) time scales, interacting withsynoptic time scales of 2 to 7 days. Thedata sets for this study were derived froma coupled Ocean-Atmosphere model thatwas able to resolve a robust MJO in itssimulations.

From the meteorological observationsrecorded onboard ORV Sagar Kanyaduring the post-monsoon season of 1999,the fluxes of sensible heat and momentumshowed smooth variation during open seacondition but they showed an increase, asthe vessel moved towards the coast. Thestandard deviations of the fluctuations ofwind velocity components andtemperature that were computed whennormalised with the respective scalingparameters, were found to obey theMonin- Obukhov similarity theory. Thecorrelation coefficients for heat andmomentum fluxes showed dependence onatmospheric stability. The drag coefficientwas found to vary with wind speed andstability. Drag coefficient under neutralcondition agreed closely with the range ofvalue quoted in the literature for thesea/ocean environment.

Under the Arabian Sea MonsoonExperiment, a national field experimentalprogramme, observations on wind (speedand direction), air temperature, relativehumidity, short wave and long waveradiation (incoming and outgoing), 5m.height turbulence measurements on windcomponents, and virtual temperature wereunder taken. Measurements on CO2 andH2O were also taken. The data are beingstudied and fruitful results are expected innear future.

The report is based on the contributionsfrom several organizations in the country.

Publications

Ali, K. 1998: Spatial distribution ofconvective clouds in north India.Atmospheric Research, 49, 1-10.

Ali, K., Chatterjee, R.N., Prakash, P.,Devara, P.C.S., Gupta, B.R.D.1998:Fractal dimensions of convective cloudsaround Delhi. Indian Journal of Radio andSpace Physics, 27, 1-6.

Anandakumar, K., Venkatesan, R., andThara Prabha, V. 2001: Soil thermalproperties at Kalpakkam in coastal southIndia. Proceedings of Indian Academy ofSciences (Earth and Planetary Science),110, 239-246.

Annes, V.H., Sijikumar, S., andMohankumar, K. 2000: Midlatitude-tropics interaction as seen from MST radarobservations at Gadanki (13.5°N, 79.2°E).Indian Journal of Radio and SpacePhysics, 29, 192-198.

Araleri, J.H., Das, D., and Srinivasan, J.2000: Bifurcation of laminar buoyant jetdischarged horizontally. Journal of FluidMechanics, 412, 61-73.

Ashok, K., Satyan, V., and Soman, M.K.2000: Simulation of monsoon transientdisturbances in a GCM. Pure and AppliedGeophysics, 157, 1509-1539.

Ashrit, R., Mandke, S.K., and Soman, M.K.1999: Sensitivity of a GCM simulation oftwo contrasting Indian monsoons to SSTanomaly distributions. Theoretical andApplied Climatology, 63, 57-64.

Ashrit, R.G., Rupa Kumar, K. and KrishnaKumar, K. 2001: ENSO-monsoonrelationships in a greenhouse warmingscenario. Geophysical Research Letters,28, 1727-1730.

Asnani, G.C. 2001: El Nino of 1997-1998and Indian monsoon. Mausam, 52, 57-66.

Asnani, G.C., Raja, M.K.R.V., andSalvekar, P.S. 2001: New insight into themicrostructure of atmospheric layer near

the tropopause. Journal of MarineAtmospheric Research, 2, 3-7.

Asnani, G.C., Rama Varma Raja, M.K.,Narayana Rao, D., Salvekar, P.S., Kishore,P., Narayana Rao, T., Venkata Ratnam,M., and Rao, P.B. 2000: Patchy layeredstructure of tropical troposphere as seen byIndian MST Radar. Indian Journal ofRadio and Space Physics, 29, 182-191.

Asoi Lal, and Sundar, R.S. 1998: Effect ofmonsoon depression of east coast at somedistant region in west. Mausam, 49, 453-460.

Asoi Lal, Sundar, R.S., and Joshi, S.P.1999: Effect of eastward moving cloudclusters over northwest India andneighbourhood on the Indian summermonsoon. Mausam, 50, 25-30.Attri, S.D., Kaushik Anubha, Rathore,L.S. and Lal, B. 2002: Water managementin wheat using non-traditional techniques.Mausam, 53, 329-336.

Attri, S.D., Lal, B., Bhan, S.C., andSrinivasan, G. 1999: Estimation of cropgrowing period in some Agroclimaticzones of India. Annals of Agri-BioResearch, 4, 1-6.

Attri, S.D., Singh, K.K., Kaushik Anubha,Rathore, L.S., Mendiratta Nisha and Lal,B. 2001: Evaluation of DynamicSimulation Model for wheat genotypesunder diverse environments in India.Mausam, 53, 561-566.

Balachandran, S., and Guhathakurta, P.1999: On the influence of QBO overNorth Indian Ocean storm and depressiontracks. Meteorology and AtmosphericPhysics, 70, 111-118.

Bandyopadhyay, A., Iyer, U., and Singh,S.S. 1999: Application of digital filteringinitialization in a limited area model overIndian region. Terrestrial, Atmosphericand Oceanic Sciences, 10, 471-490.

Bansod, S.D., Prasad, K.D., and Singh,S.V. 2000: Stratospheric zonal wind andtemperature in relation to summer

monsoon rainfall over India. Theoreticaland Applied Climatology, 67, 115-121.

Bapiraju, B., Balasubrahmanyam, P.,Nasir Hussain, S., Aleem Basha H., andDutta, G. 2000: Different methods tostudy gravity wave variance – Acomparison. Indian Journal of Radio andSpace Physics, 29, 235-238.

Bawiskar, S.M., Chipade, M.D., andSingh, S.S. 2002: Energetics of zonalwaves during different phases of monsoon.Mausam, 53, 1-8.

Bawiskar, S.M., Mujumdar, V.R., andSingh, S.S. 2002: Momentum transport ofwave zero during March: A possiblepredictor for the Indian summer monsoon.Procedings of Indian Academy ofSciences (Earth and Planetary Sciences),111, 153-162.

Behera, S.K., Krishnan, R., and Yamagata,T. 1999: Unusual ocean-atmosphericconditions in the tropical Indian Oceanduring 1994. Geophysical ResearchLetters, 26, 3001-3004.

Behera, S.K., Salvekar, P.S., andYamagata, T. 2000: Simulation ofinterannual SST variability in the tropicalIndian Ocean. Journal of Climate, 13,3487-3499.

Behera, S.K., Salvekar, P.S., Ganer, D.W.,Deo, A.A. 1998: Interannual variability insimulated circulation along east coast ofIndia. Indian Journal of Marine Science,27, 115-120.

Beig, G. 2000: Perturbation inatmospheric charged species after theeruption of Mount Pinatubo. GeophysicalResearch Letters, 27, 2497-2500.

Beig, G. 2000: Relative importance ofsolar activity and anthropogenic influenceson the ion composition, temperature andassociated neutrals of the middleatmosphere. Journal of GeophysicalResearch, 105, 19841-19856.

Beig, G. 2001: Model evolution of themiddle atmospheric palaeoenvironments.Mausam, 52, 297-306.

Beig, G., and Brasseur, G. P.1999:Anthropogenic perturbations oftropospheric ion composition. GeophysicalResearch Letters, 26, 1303-1306.

Beig, G., and Brasseur, G.P. 2000: Modelof tropospheric ion composition: a firstattempt. Journal of Geophysical Research,105, 22671- 22684.

Beig, G., and Fadnavis, S. 2001: In searchof greenhouse signals in the equatorialmiddle atmosphere. Geophysical ResearchLetters, 28, 4603-4606

Bhat, G.S 2001: Near surface atmosphericcharacteristics over the North Bay ofBengal during the Indian summermonsoon. Geophysical Research Letters,28, 987-990.

Bhat, G.S. 1998: The dependence of deepcloud mass flux and area cover onconvective and large-scale processes.Journal of Atmospheric Science, 55, 2993-2999.

B h a t , G . S . , A m e e n u l l a , S . ,Venkataramana, M., and Sengupata, K.2000: Atmospheric boundary layercharacteristics during the BOBMEX-Pilotexperiment. Proceedings of IndianAcademy of Sciences (Earth and PlanetarySciences), 109, 229-237.

Bhat, G.S., and Krothapalli, A. 2000:Simulation of a round jet and a plume in aregional atmospheric model. MonthlyWeather Review, 128, 4108-4117.

Bhat, G.S., Chakraborty, A., Nanjundiah,R.S., and Srinivasan, J. 2002: Verticalthermal structure of atmosphere duringactive and weak phases of convection overthe north Bay of Bengal: Observations andmodel results. Current Science, 83, 296-302.

Bhat, G.S., Gadgil, S., Hareesh Kumar,P.V., Kalsi, S.R., Madhusoodanan, P.,

Murty, V.S.N., Prasada Rao, C.V.K.,Ramesh Babu, V., Rao, L.V.G., Rao, R.R.,Ravichandran, M., Reddy, K.G., SanjeevaRao, P., Sengupta D., Sikka, D.R., Swain,J. and Vinayachandran, P.N. 2001:BOBMEX – the Bay of Bengal MonsoonExperiment, Bulletin of AmericanMeteorological Society, 82, 10, 2217-2243.

Bhatia, R.C., Khanna, P.N., Prasad, K. andRama Rao, Y.V. 1999: A preliminarystudy of the impact of NOAA soundingsretrievals on a limited area model (LAM)forecasts. Vayumandal, 29, 147-149.

Bhatla, R., and Chattopadhyay, J. 1999:Association between mid-latitudecirculation and Indian monsoon rainfall.Mausam, 50, 37-52.Bhavani Kumar, Y., Siva Kumar, V., Rao,P.B., Krishnaiah, M., Kohei Mizutani,Tetsu Aoki, Motiaki Yasui and Itable.2000: Middle atmospheric temperaturemeasurements using ground basedinstrument at a low latitude. Indian Journalof Radio and Space Physics, 29, 249-257.

Biswas, N.C., De, U.S., and Sikka, D.R.1998: The role of Himalayan Massif –Tibetan Plateau and the mid-troposphericsub-tropical ridge over north India duringthe advance phase of the southwestmonsoon. Mausam, 49, 285-300.

Borgaonkar, H.P., and Pant, G.B. 2001:Long-term climate variability overmonsoon Asia as revealed by some proxysources. Mausam, 52, 9-22.

Borgaonkar, H.P., Pant, G.B., and RupaKumar, K. 1999: Tree-ring chronologiesfrom Western Himalayas and theirdendroclimatic potential. IAWA Journal,20, 295-309.

Chakrabarty, D.K., Peshin, S.K., Pandya,K.V., and Shah, N.C. 1998: Long-termtrend of ozone column over the Indianregion. Journal of Geophysical Research,103, 19245-19251.

Chakrabarty, D.K., Peshin, S.K.,Srivastav, S.K., Shah, N.C., and Pandya,

K.V. 2001: Further evidence of total ozonevariation during the solar eclipse of 1995.Journal of Geophysical Research, 106,3213-3218.

Chakrabary, D.K., Shah, N.C., Pandya,K.V. and Peshin, S.K. 2000: Long termtrend of tropopause over New Delhi andThiruvananthapuram. GeophysicalResearch Letters, 27, 2181-2184.Chakraborty, A., Upadyayaya, H.C.,Sharma, O. P. 2000: Response of an oceangeneral circulation model to wind andthermodynamic forcings. Procedings ofIndian Academy of Sciences (Earth andPlanetary Sciences). 109, 329-337.

Chakraborty, D.R., and Agarwal, N.K.2000: Divergent rotational nonlinearenergy conversions in wave numberfrequency domain during summermonsoon. Pure and Applied Geophysics,157, 1781-1795.

Chakraborty, D.R., and Tewari, M. 2001:Aspects of low frequency oscillationduring the Northern winter as inferredfrom nonlinear energy interactions. Pureand Applied Geophysics, 158, 1065-1074.

Chattopadhyay, J., and Bhatla, R. 2002:Possible influence of QBO onteleconnections relating Indian summermonsoon rainfall and sea surfacetemperature anomalies across theequatorial Pacific. International Journal ofClimatology, 22,121-127.

Chintalu, G.R., Seetaramayya, P.,Ravichandran, M., and Mahajan, P.N.2001: Response of the Bay of Bengal toGopalpur and Paradip super cyclonesduring 15-31 October 1999. CurrentScience, 81, 283-291.

Dahale, S.D., and Puranik, P.V. 2000:Climatology and predictability of thespatial coverage of 5-day rainfall overIndian subdivisions. International Journalof Climatology, 20, 443-453.

Daoo, V.J., and Krishnamoorthy, T.M.2000: Extreme value analysis ofmeteorological elements at Trombay,

Mumbai. Indian Journal of Radio andSpace Physics, 29, 304-308.

Das, M.R., Mukhopadhyay, R.K.,Dandekar, M.M., and Kshirsagar, S.R.2002: Premonsoon Western Disturbancesin relation to monsoon rainfall and itsadvancement over NW India and theirtrends. Current Science, 82, 1320-1331.

Dash, S.K. 1998: Role of seasonal cycleforcing in simulating the summermonsoon circulation and precipitation,Indian Journal of Marine Science, 27, 97-103.

Datta, S.N., and De, U.S. 1999: Adiagnostic study of contrasting rainfallepochs over Mumbai. Mausam, 50, 1-8.

De, S., and Subramanyam, D. 1999: Roleof monsoon zonal flow on CISKinstability and vice-versa: a sensitivitystudy. Indian Journal of Radio and SpacePhysics, 28, 232-239.

De, U.S. 2001: Climate change impact;Regional scenario. Mausam, 52, 201-212.De, U.S., and Mazumdar, A.B. 1999:Principal components of rainfall regimeand associated synoptic models ofsouthwest monsoon over India.Theoretical and Applied Climatology, 64,213-218.

De, U.S., and Mukhopadhyay, R.K. 1999:The effect of ENSO/Anti-ENSO onnortheast monsoon rainfall. Mausam, 50,343-354.

De, U.S., and Mukhopadhyay, R.K. 2002:Breaks in monsoon and related precursors.Mausam, 53, 309-318.

De, U.S., Prakasa Rao, G.S., and Jaswal,A.K. 2001: Visibility over Indian airportsduring winter season. Mausam, 52, 717-726.

De, U.S . , Ra tnam, K. , andMukhopadhyay, R.K. 1999: Zonal windvariation in the stratosphere andmesosphere over the equatorial region ofAsia and possible association with Indian

summer monsoon rainfall. Mausam, 50,243-250.

Debaje, S.B. 2000: Tropospheric ozone:an emerging problem in the urbanenvironment. Current Science, 78, 770-771.

Debaje, S.B., and Jadhav, D.B. 1999:Eulerian photochemical model fortropospheric ozone over the tropics. CurrentScience, 77, 1537-1541.

Debnath, G.C., and Samui, R.P. 1998:Oscillation of Potential Evapotranspirationin India and its significance on seasonalpotential water requirement of crops.Mausam, 49, 387-394.Deo, A.A., Salvekar, P.S. and Behera,S.K. 2001: Oceanic response to cyclonemoving in different directions over Indianseas using IRG model. Mausam, 52, 163-174.

Desai, D.S., Waykar, B.D., and Nerlekar,S.B. 1999: Heat wave conditions duringMarch to June for the years 1972, 1979and 1989 and their comparison with years1990-95. Mausam, 50, 211-214.

Deshpande, C.G., and Kamra, A.K. 2001:Diurnal variations of the atmosphericelectric field and conductivity at Maitri,Antarctica. Journal of GeophysicalResearch, 106, 14207-14218.

Devara, P.C.S. 2000: Study of Physico-chemical and optical properties ofatmospheric constituents under differentenvironmental and meteorologicalconditions in India-Part II: trace gases.Indian Journal of EnvironmentalProtection, 20, 15-22.

Devara, P.C.S., Maheskumar, R.S., Raj,P.E., Dani, K.K., Pandithurai, G., andRao, Y.J. 1999: Correlative measurementsof aerosol optical depth and sizedistribution around INDOEX-IFP98 frommulti-spectral solar radiometry. CurrentScience, 76, 977-980.

Devara, P.C.S., Maheskumar, R.S., Raj,P.E., Pandithurai, G., and Dani, K.K.

2002: Recent trends in aerosol climatologyand air pollution as inferred from multi-year lidar observations over a tropicalurban station, International Journal ofClimatology, 22, 435-449.

Devara, P.C.S., Raj, P.E., Maheskumar,R.S., Dani, K.K., and Pandithurai, G.1999: Ground-based lidar study of aerosoland boundary layer characteristics duringINDOEX first field phase. CurrentScience, 76, 973-976.

Dhaka, S.K., Devarajan, P.K, Shibagaki,Y., Choudhary, R.K., Fukao, S. 2001:Indian MST radar observations of gravitywave activities associated with tropicalconvection. Journal of Atmosphere Solarand Terrestrial Physics, 63, 1631-1642.

Dhanna Singh, Bhadram, C.V.V., andMandal, G.S. 1998: Intensity of heat lowduring May and interannual variability ofIndian summer monsoon rainfall.Vayumandal, 27, 3 - 4.

Dhanorkar, S.S., and Kamra, A.K. 2001:Effect of coagulation on the particlecharge distribution and air conductivity,Journal of Geophysical Research, 106,12055-12065.

Dhar, O.N., and Nandargi, S.S. 1999: Roleof low pressure areas in the absence oftropical disturbances during monsoonmonths in India. International Journal ofClimatology, 19, 1153-1159.

Dhar, O.N., and Nandargi, S.S. 2000:Appraisal of precipitation distributionaround Everest and Kanchenjunga peaksin the Himalayas. Weather, 55, 223-233.

Dhar, O.N., and Nandargi, S.S. 2000:Study of rainfall and floods in theBrahmaputra basin in India. InternationalJournal of Climatology, 27, 771-781.

Dugam, S.S., and Kakade, S.B. 1999:Global temperature and monsoon activity.Procedings of Indian Academy ofSciences (Earth and Planetary Sciences),108, 303-307.

D u t t a , G . , B a p i r a j u , B . ,Balasubramanyam, P., and Aleem Bhasha,H. 1999: VHF radar observations ofgravity waves at a low latitude. AnnalesGeophysicae, 17, 1012-1019.

Dutta, S.N. 2001: Momentum Flux,Energy Flux and Pressure Drag associatedwith Mountain Wave across WesternGhat. Mausam, 52, 325-332.

Gadgil Sulochana, Sajani, S. 1998:Monsoon precipitation in the AMIP runs.Climate Dynamics, 14, 659-689.

Gadgil, S., Seshagiri Rao, P.R., andNarahari Rao, K. 2002: Use of climateinformation for farm-level decisionmaking: rainfed groundnut in southernIndia. Agricultural Systems, 74, 431-457.

Gadgil, S., Srinivasan. J., Nanjundiah,R.S., Krishna Kumar, K., Munot, A.A.,and Rupa Kumar, K. 2002: On forecastingthe Indian summer monsoon: Theintriguing season of 2002. CurrentScience, 83, 394-404.

Gairola, R.M., Basu, S., Pandey, P.C.2001: Eddy detection over southern IndianOcean using TOPEX/POSEIDONaltimeter data. Marine Geodescy, 24, 107-121.

Gambheer, A.V., and Bhat, G.S. 2000:Life Cycle characteristics of deep cloudsystems over the Indian region usingINSAT-1B Pixel Data. Monthly WeatherReview, 128, 4071-4083.

Ganesan, G.S., Muthuchami, A.,Ponnuswamy, A. S. 2001: Various classesof rainfall in the coastal stations of TamilNadu. Mausam, 52, 433-436.

Ganesan, G.S., Muthuchami, A.,Ponnuswamy, A.S. 2000: Heavy rain atChennai and its relation to cyclonicdisturbances. Mausam, 51, 17-24.

Gangadharan, V.K., Sasidharan, N.V.,Santhosh K. 1999: A study of heat islandintensities at Thiruvananthapuram on acold winter night. Mausam, 50, 106-108.

George, J.P. 2001: Shortwave radiativeforcing by mineral dust aerosols overArabian Sea: A model study. CurrentScience, 80, 97-99.

Ghosh, A.K., Jain, A.R., and Siva Kumar,V. 2000: Characterization of atmosphericwinds associated shear and turbulence:Indian MST radar during summermonsoon. Indian Journal of Radio andSpace Physics, 29, 222-230.

Gnanaseelan, C., Ganer, D.W.,Annapurnaiah, K., Deo, A.A., andSalvekar, P.S. 2001: Seasonal heattransport in the North Indian Ocean duringtwo contrasting monsoons. Journal ofIndian Geophysical Union, 5, 51-56

Gopalakrishnan, V., and Kamra, A.K.1999: Measurements of the atmosphericelectric field and conductivity made overIndian Ocean during December 1996-January 1997. Current Science, 76, 990-993.

Gore, P.G., and Sinha Ray, K.C. 2002:Variability in drought incidence overdistricts of Maharashtra. Mausam, 53,533-542.

Gore, P.G., and Thapliyal V. 2000:Occurrence of dry and wet weeks overMaharashtra. Mausam, 51, 25-38.

Goswami, B.N. 1998: Interannualvariations of Indian summer monsoon in aGCM: External conditions versus internalfeedbacks. Journal of Climate, 11, 501-522.

Goswami, B.N. 1998: The physics ofENSO-monsoon connection. IndianJournal of Marine Science, 27, 82-89.

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Goswami, B.N., and Ajaya Mohan, R.S.2000: A common spatial mode for intra-seasonal and interannual variation and

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Parameswarn, K., Prabha Nair, R., RekhaRajan and Venkata Ramana, M. 1999:Aerosol loading in the coastal and marineenvironments in the Indian Ocean regionduring the winter season, Current Science,76, 347-355.

Parameswarn, K., Rekha Rajan,Vijayakumar, G., Rajeev, K., KrishnaMoorthy, K., Nair, P.R., and Satheesh,S.K. 1998: Seasonal and Long termvariations in Aerosol Content in theAtmospheric Mixing Region at a TropicalStation in the Arabian Sea Coast. Journalof Atmospheric Solar and TerrestrialPhysics, 60, 17-25.

Parasnis, S.S., Kulkarni, M.K., and Pillai,J.S. 2001: Simulation of boundary layerparameters using one-dimensionalatmospheric boundary layer model.Journal of Agrometeorology, 3, 261-266.

Patil, M.N., and Parasnis, S.S. 2001: Onthe stability of atmospheric surface layeralong the monsoon trough region overIndia. Indian Journal of Radio and SpacePhysics, 30, 266-272.Patil, M.N., Murthy, B.S., and Parasnis,S.S. 2001: Characteristics of momentumand sensible heat flux during the monsoonconditions over LASPEX-97 region,Journal of Agrometeorology, 3, 107-117.

Patra, P.K., Lal, S., Venkataramani, S.,Gauns, M., and Sarma, V.V.S.S. 1998:Seasonal variability in distribution andfluxes of methane in the Arabian Sea.Journal of Geophysical Research, 103 C,1167-1176.

Pattanaik, D.R., and Satyan, V. 2000:Effect of cumulus parameterisation on theIndian summer monsoon simulated by theCOLA General Circulation Model. Journalof Meteorological Society of Japan, 78,701-717.

Pattanaik, D.R., and Satyan, V. 2000:Effect of cumulus parameterisation on theIndian summer monsoon simulated by theCOLA general circulation model. Journalof Meteorological Society of Japan, 78,701-717.

Pattanaik, D.R., and Satyan, V. 2000:Fluctuations of tropical easterly jet duringcontrasting monsoons over India: a GCMstudy. Meteorology and AtmosphericPhysics, 75, 51-60.Pattanaik, D.R., Muzumdar Milind,Krishnan, R., and Satyan, V. 1999: GCMsimulation of Indian summer monsoon–2001. Vayu Mandal, 3-6.

Patwardhan, S.K., and Asnani, G.C. 2000:Mesoscale distribution of summermonsoon rainfall near the Western ghats(India). International Journal ofClimatology, 20, 575-581.

Patwardhan, S.K., and Bhalme, H.N.2001: Study of cyclonic disturbances overIndia and the adjacent ocean. InternationalJournal of Climatology, 21, 527-534

Paul, S.K. 1999: Characteristics of clouddrop spectra on rain and non-rain occasions.Indian Journal of Radio and Space Physics,28, 170-176.

Paul, S.K. 1999: Velocities of water dropsfalling in oil media and the wake effect.Indian Journal of Radio and Space Physics,28, 15-21.

Paul, S.K. 2000: Study of chlorideaerosol, total aerosol and ice nuclei in theIndian regions. Pure and AppliedGeophysics, 157, 1541-1556.

Paul, S.K. 2000: Characteristics of clouddrop spectra at different levels withrespect to cloud thickness. Pure andApplied Geophysics, 157, 1557-1569.

Paul, S.K. 2000: Cloud drop spectra atdifferent levels and with respect to cloudthickness and rain. Atmospheric Research,52, 303-314.

Pawar, S.D., and Kamra, A.K. 2000:Comparative measurements of theatmospheric electric space charge densitymade with the filtration and Faraday Cagetechniques. Atmospheric Research, 54,105-116.

Peshin, S.J., Dewhare, J.N., Bhatia, R.C.and Srivastava, S.K 2000: Recent changesobserved in column ozone concentrationover India. Mausam, 51, 69-74.Peshin, S.K., Mandal, T.K., Smit, H.G.J.,Srivastav, S.K. and Mitra, A.P. 2001:Observation of vertical distribution oftropospheric ozone over Indian ocean andits comparison with continental profilesduring INDOEX FFP-1998 and IFP-1999.Current Science. 80, 197-208.

Peshin, S.K., Rao, Rajesh P., andSrivastava, S.K. 1998: Result ofintercomparison and calibration of DobsonSpectrophotometer Japan – 1995.Mausam, 49, 371-374.

Pillai, A.G., Momin, G.A., Naik, M.S.,Rao, P.S.P., Safai, P.D., and Ali, K. 2001:Studies of atmospheric aerosols and ozonein different environments. Journal ofMarine Atmospheric Research, 2, 33-36.

Pillai, A.G., Naik, M.S., Momin, G.A.,Rao, P.S.P., Safai, P.D., Ali, K., Rodhe, H.and Granat, L. 2001: Studies of wetdeposition and dustfall at Pune, India.Water, Air and Soil Pollution, 130, 475-480.

Prabha Nair, R., and Krishna Moorthy, K.1998: An analysis of the effects of MountPinatubo aerosols on atmosphericradiances, International Journal of RemoteSensing. 19(4), 697-705.

Prabha Nair, R., and Krishna Moorthy, K.1998: Effects of changes in theatmospheric water vapour content on thephysical properties of atmosphericaerosols at a coastal station. Journal ofAtmospheric and Solar Terrestrial Physics60, 563-572.

Prasad, K., Kalsi, S.R., Rama Rao, Y.V.,Roy Bhowmik, S.K., Joardar, D. 2000:

Evaluation of operational cyclone trackforecasting by a limited area NWP modelduring 1998. Mausam, 51, 91-95.

Prasad, K.D., and Bansod, S.D. 2000:Interannual variations of the outgoinglong-wave radiation and the Indiansummer monsoon rainfall. InternationalJournal of Climatology, 20, 1955-1964.

Prasad, K.D., Bansod, S.D., and Sabade,S.S. 2000: Forecasting Indian summermonsoon rainfall by outgoing longwaveradiation over the Indian Ocean.International Journal of Climatology, 20,105-114.

Raghavan, S. 1999: The tropical cyclonewith the smallest eye. Mausam, 50, 1, 105.

Raghunath, K., Bhavani Kumar, Y, SivaKumar, V, Rao, P.B., Kohei Mizutani,Tetsu Aoki, Motiaki Yasui and Itable.2000: Indo-Japanese Lidar observations ofaerosols over a tropical latitude. IndianJournal of Radio and Space Physics, 29,239-244.

Raj, P.E., Devara, P.C.S., Maheskumar,R.S., Pandithurai, G., and Dani, K.K.2002: Lidar-derived aerosol concentrationand their relationship with horizontalwinds over an urban location. Mausam,53, 145-152.Raj, Y.E.A. 1998: A scheme for advanceprediction of northeast monsoon rainfall ofTamil Nadu. Mausam, 49, 247-254.

Raj, Y.E.A., Nageshwari, P. 2000:Development, decay and duration ofwinter land breeze over Chennai.Mausam, 51, 184-186.

Raja, M.K.R.V., Asnani, G.C., Salvekar,P.S., Jain, A.R., Rao, D.N., Rao, S.V.,Kishore, P., and Hareesh, M. 1999:Layered clouds in the Indian monsoonregion. Proceedings of Indian Academy ofSciences (Earth and Planetary Sciences),108, 287-295.

Rajeev, K. and Parameswarn, K. 1998:Iterative method for the inversion ofmultiwavelength lidar signals to determine

aerosol size distribution. Applied Optics,37, 4690-4700.

Rajeev, K., Ramanathan, V. andMeywerk, J. 2000: Regional aerosoldistribution and its long-range transportover the Indian Ocean. Journal ofGeophysical Research, 105, 2029-2043.

Rajeevan, M. 1998: Aerosole-cloud-climate effect: study with a radiativetransfer model. Mausam, 49, 195-202.

Rajeevan, M. 1998: Model calculations ofnon-cloud radiative forcing of sulphateaerosol. Mausam, 49, 45-58.

Rajeevan, M. 2001: Interactions amongdeep convection, sea surface temperatureand radiation in the Asian monsoonregion. Mausam, 52, 83-96.

Rajeevan, M., and Srinivasan, J. 2000: Netcloud radiative forcing at the top of theatmosphere in the Asian monsoon region.Journal of Climate, 13, 650-657.

Rajeevan, M., Pai, D.S., and Thapliyal, V.2002: Predictive relationships betweenIndian Ocean sea surface temperature andIndian summer monsoon. Mausam, 53,337-348.

Rajeevan, M., Pai, D.S., and Thapliyal, V.1999: Spatial and temporal relationshipsbetween global land surface airtemperature anomalies and Indian summermonsoon. Meteorology and AtmosphericPhysics, 66, 157-171.

Rajeevan, M., Thapliyal, V., Patil, S.R.,and De, U.S. 1999: Canonical CorrelationAnalysis (CCA) model for Long RangeForecast of subdivisional monsoon rainfallover India. Mausam , 50, 145-152.

Rajendra Kumar, J., and Dash, S.K. 1999:Interannual and intraseasonal variations ofsome characteristics of monsoondisturbances form over the Bay. Mausam,50, 55-62.

Rajendra Kumar, J., and Dash, S.K. 2001:Interdecadal variations of characteristics

of monsoon disturbances and their epochalrelationships with rainfall and othertropical features. International Journal ofClimatology, 21, 759-771.

Rajendra Kumar, J., and Desai, D.S. 1999:Monsoon Variability in recent years fromsynoptic scale disturbances and semi-permanent systems. Mausam, 50, 35-144.

Rajendran, K., Nanjundiah, R.S., andSrinivasan, J. 2002: The impact of surfacehydrology on the simulation of tropicalintraseasonal oscillation in NCARCCM2atmospheric GCM. Journal ofMeteorological Society of Japan, 80,1357-1381.

Rajendran, K., Nanjundiah, R.S., andSrinivasan, J., 2002: Comparison ofseasonal and intraseasonal variation oftropical climate in NCAR CCM2 GCMwith two different cumulus schemes.Meteorology and Atmospheric Physics,79, 57-86.

Rama Rao, Y.V., Prasad, K., and Prasad,Sant. 2001: A case study of the impact ofINSAT derived humidity profiles onprecipitation forecast by limited areamodel. Mausam, 52, 647-654.

Rameshan, K., and Goswami, P. 1999:Mechanism of broad spectrum variabilitiesin the tropics. Geophysical ResearchLetters, 27, 323-326.

Ramesh Kumar, M.R., Schlussel, P. 1998:Air-sea interaction over the indian oceanduring the two contrasting monsoon years1987 and 1988 studied with satellite data.Theoretical and Applied Climatology, 60,219-231.

Ramesh Kumar, M.R., Muraleedharan,P.M., Sathe, P.V. 1999: On the role of seasurface temperature variability over thetropical indian ocean in relation to summermonsoon using satellite data. RemoteSensing Environment, 70, 238-244.

Ramesh Kumar, M.R., Shenoi, S.S.C.,Schluessel, P. 1999: On the role of thecross equatorial flow on summer monsoon

rainfall over India using NCEP/NCARreanalysis data. Meteorology andAtmospheric Physics, 70, 201-213.

Rao Bhaskar, D.V. 2001: Trends andfluctuations of the cyclonic systems overNorth Indian Ocean. Mausam 52,1-8.

Rao, D.N., Singh, H.R., Kulkarni, J.R.,Chandrika, A.Y., and Rao, V.B. 2000:Vertical variation of Madden-Julianoscillations in the normal monsoon seasonas revealed through MST radar wind data.Meteorology and Atmospheric Physics,73, 55-59.

Rao, D.N., Singh, H.R., Rao, S.V.B, Raja,M.K.R.V., Asnani, G.C., and Thulsiraman,S. 1999: Estimation of meridionaltemperature gradient profile using IndianMST radar. Indian Journal of Radio andSpace Physics, 28, 165-169.

Rao, D.N., Tulasiraman, S, Rao, S.V.B,Rao, T.N., Kishore, P., Ratnam, M.V., andKrishna Reddy, K. 2000: VHF radarobservations of tropical easterly jet streamover Gadanki. Advanced Space Research,26, 943-946.Rao, K., Narahari, Sulochana Gadgil,Seshagiri Rao, P.R., and Savithri, K. 2000:Tailoring strategies to rainfall variability –1: the choice of the sowing window.Current Science, 78, 1216-1230.

Rao, P.S.P., Momin, G.A., Safai, P.D.,Ali, K., Naik, M.S., and Pillai, A.G. 2001:Aerosol and trace gas studies at Puneduring INDOEX IFP 99. Current Science,80, 105-109.

Rao, R.R., and Sivakumar, R. 2000:Seasonal variability of the heat budget ofthe mixed layer and the near-surface layerthermal structure of the tropical IndianOcean from a new global oceantemperature climatology. Journal ofGeophysical Research, 105C, 995-1015.

Rao, R.R., and Sivakumar, R. 1999: Onthe possible mechanisms of the evolutionof a mini-warm pool during the pre-summer monsoon season and the onsetvortex in the southeastern Arabian Sea.

Quarterly Journal of Royal MeteorologicalSociety, 125, 787-809.

Ray, T.K., Sinha, D., and Guhathakurta, P.2000: Landslides in India. Vayumandal,30, 1-2.

Revathy, K., Prabhakaran Nayar, andKrishna Murthy, B.V. 2001: Diurnalvariation of tropospheric temperature at atropical station. Annales Geophysicae, 19,1001-1005.

Roy Bhowmik, S.K. 2002: Evaluation ofbroad scale circulation and thermalanomalies in relation to Onset of Indiansummer monsoon. International Journalof Climate, 22, 649-661.

Roy Bhowmik, S.K., and Prasad, K. 2001:Some characteristics of limited area modelprecipitation forecast of Indian monsoonand evaluation of associated flow features.Meteorology and Atmospheric Physics,76, 223-236.

Rupa Kumar, K., and Ashrit, R.G. 2001:Regional aspects of global climate changesimulations: validation and assessment ofclimate response over Indian monsoonregion to transient increase of greenhousegases and sulfate aerosols. Mausam, 52,229-244.

Sadani, L.K., and Kulkarni, J.R. 2001:Study of coherent structures in theatmospheric surface layer over short andtall grass. Boundary Layer Meteorology,99, 317-334.

Sadhuram, Y., Rao, D.P. 1998: Moisturesource for summer monsoon rainfall overIndia. Indian Journal of AppliedHydrology, 11, 63-70.

Safai, P.D., Rao, P.S.P., Momin, G. A.,Ali, K., Tiwari, S., and Naik, M.S. 2002:Chemical composition of size separatedaerosols at two rural locations in theHimalayan region. Indian Journal of Radioand Space Physics, 30, 270-277.

Sahai, A.K. 1999: Thermosolutalconvection in the presence of both vertical

and horizontal temperature gradients.Journal of Applied Mechanics, 66, 181-196.

Sahai, A.K., Soman, M.K., and Satyan, V.2000: All India summer monsoon rainfallprediction using artificial neural network.Climate Dynamics, 16, 291-302.Sa j i , N .H. , Goswami , B .N . ,Vinayachandran, P.N., and Yamagata, T.1999: A dipole mode in the tropical IdnianOcean. Nature, 401, 360-363.

Salvekar, P.S., Ganer, D.W., Deo, A.A.,Reddy, P.R., Basu, S., and Raj Kumar2002: Numerical simulation of NorthIndian Ocean state prior to the onset ofSW monsoon using SSM/I winds. MarineGeodesy, 25, 115-131.

Sam, N .V . , Mohan ty , U .C . ,Satyanarayana, A.N.V., Raju, P.V.S.2001: A study on air sea exchangeprocesses and conserved variable analysisover the Indian Ocean with INDOEX IFP-99 data. Current Science, 80, 46-54.

Sanjay, J., Mukhopadhyay, P., and Singh,S.S. 2002: Impact of nonlocal boundary-layer diffusion scheme on forecasts overIndian region. Meteorology andAtmospheric Physics, 80, 207-216.

Sasi, M.N., and Vijayan, L. 2001:Turbulence characteristics in the tropicalmesosphere as obtained by MST radar atGadanki (13.5°N, 79.2°E). AnnalesGeophysicae, 19, 1019-1025.

Sasi, M.N., Lakshmi Vijayan, Deepa, V.,and Krishna Murthy, B.V. 1999:Estimation of equatorial wave momentumfluxes using MST radar winds at Gadanki(13.5°N, 79.2°E). Journal of AtmosphericSolar and Terrestrial Physics, 61, 377-384.

Sasi, M.N., Ramkumar, G., and Deepa, V.2001: Tidal wind oscillations in thetropical lower atmosphere as observed byIndian MST radar. Annales Geophysicae,19, 991-999.

Satheesh, S.K. 2002: Aerosol radiativeforcing by Indian Ocean Aerosols: Effect

of cloud and surface reflection. AnnalesGeophysicae, 20, 2105-2109.

Satheesh, S.K. 2002: Aerosol radiativeforcing over Tropical Indian Ocean,Modulation by Sea-surface winds. CurrentScience, 82, 310-316.

Satheesh, S.K., Krishnamoorthy, K., andKrishnamurthy, B.V. 1998: Spatialgradients in aerosol characteristics overthe Arabian Sea and Indian Ocean. Journalof Geophysical Research, 103D, 26183-26192.

Satyanarayana, A.N.V., Mohanty, U.C.,Niyogi, D.S., Raman, S., Lykossov, V.N.,Warrior, H., Sam, N.V. 2001: A study onmarine boundary layer processes in theITCZ and non-ITCZ regimes over IndianOcean with INDOEX IFP-99 data. CurrentScience, 80, 39- 45.

Satyanarayana, A.N.V., Mohanty, U.C.,Sam, N.V., Basu, S., Lyla, P.S. 2000:Numerical simulation of the marineboundary layer characteristics over theBay of Bengal as revealed by BOBMEX-98 Pilot experiment. Procedings of IndianAcademy of Sciences (Earth and PlanetSciences), 109, 293-303.

Selvam, A.M. 1999: Fractal spacetime andinformation in neural network of thehuman brain. Chaos, Solitons and Fractals,10, 25-29.

Selvam, A.M., and Fadanvis, S.S. 1999:Cantorian fractal spacetime, quantum-likechaos and scale relativity in atmosphericflows. Chaos, Solitons and Fractals, 10,1577-1582.

Selvam, A.M., and Fadanvis, S.S. 1999:S u p e r s t r i n g s , c a n t o r i a n - f r a c t a lspacetime, quantum-like chaos inatmospheric flows. Chaos, Solitons andFractals, 10, 1321-1334.

Selvam, A.M., Sen, D., and Mody, S.M.S.1999: Critical fluctuations in dailyincidence of acute myocardial infarction.Chaos, Solitons and Fractals, 10, 1612-1617.

Sengupta, D, Goswami, B.N., and RetishSenan, 2001: Coherent intraseasonaloscillations of ocean and atmosphereduring the Asian summer monsoon,Geophysical Research Letters, 28, 4127-4131.

Sengupta, D, Senan, R., and Goswami,B.N. 2001 :Origin of intra-seasonalvariability of circulation in the tropicalcentral Indian Ocean. GeophysicalResearch Letters, 28, 1267-1270.

Sengupta, D., and Ravichandran, N.M.2001: Oscillations of Bay of Bengal seasurface temperature during the 1998summer monsoon. Geophysical ResearchLetters, 28, 2033-2036.

Shaji, C., Bahulayan, N., Rao, A.D., andDube, S.K. 1998: Various approaches tothe modelling of large scale 3-dimensionalcirculation in the Ocean. Indian Journal ofMarine Science, 27, 104-114.

Shankar, D. and Shetye, S.R. 1999: Areinterdecadal sea level changes along theIndian coast influenced by variability ofmonsoon rainfall? Journal of GeophysicalResearch, 104 C, 26031-26042.

Shankar, D., and Shetye, S.R. 2001: Whyis mean sea level along the Indian coasthigher in the Bay of Bengal than theArabian Sea? Geophysical ResearchLetters, 28, 563-565.

Sharma, R.V. 1999: Flow characteristicsin Indian Ocean equatorial region duringpre-onset phase of south- west monsoon1984, Mausam, 51, 177-179.

Sharma, R.V., Thakur Prasad and ShravanKumar, 2000: Some aspects of zonal windprofiles along west coast of India duringmonsoon. Vayu Mandal, 30, 1-2.

Shende, R.R., and Chivate, V.R. 2000:Global and diffuse solar radiant exposuresat Pune. Mausam, 51, 349-358.

Shenoi, S.S.C., Shankar, D., and Shetye,S.R. 2002: Differences in heat budgets of

the near-surface Arabian Sea and Bay ofBengal: implications for the summermonsoon. Journal of GeophysicalResearch, 107, 5.1-5.14.

Shenoi, S.S.C., Shankar, D., and Shetye,S.R. 1999: On the sea surface temperaturehigh in the Lakshadweep sea before theonset of the southwest monsoon. Journalof Geophysical Research, 104 C, 15703-15712.

Shenoy, D.M., DileepKumar, M., andSarma, V.V.S.S. 2000: Controls ofdimethyl sulphide in the Bay of Bengalduring BOBMEX-Pilot cruise 1998.Proceedings of Indian Academy ofSciences (Earth and Planetary Sciences),109, 279-283.

Shravan Kumar, Thakur Prasad andAshalata Agrawal.1999: A synoptic –Climatic study of the onset of south westmonsoon over Mumbai. Proceedings ofIndian Academy of Sciences (EarthPlanetary Sciences), 108, 321-326.

Shravan Kumar, Thakur Prasad,Sasidharan, N.V., and Sushma Nair K.,2001: Heat Island Intensities over BrihanMumbai on a cold winter and hot summernight. Mausam, 52, 703-708.

Singh, A.K., Singh, D.K., and Singh, R.P.1999: Estimation of ionosphericparameters by propagat ion ofelectromagnetic waves at low latitude.Indian Journal of Physics, 75 B, 315-320.

Singh, D. K., and Singh R., P. 2002:Resonance energy, growth rate andmagnetic field intensity of the ELFemission at low latitude. Indian Journal ofRadio and Space Physics, 31, 75-81.

Singh, D.K., Patel, R.P., and Singh, R.P.2001: Auroral and low latitude VLF hiss.Indian Journal of Radio and SpacePhysics, 30, 24-30.

Singh, G.P., and Chattopadhyay, J. 1998:Relationship between mid-latitudecirculation indices and Indian northeast

monsoon rainfall. Pure and AppliedGeophysics, 151, 811-818.

Singh, G.P., and Chattopadhyay, J. 1998:Relationship of tropospheric temperatureanomaly with Indian southwest monsoonrainfall. International Journal ofClimatology, 19, 759-763.

Singh, N., and Patwardhan, S.K. 2001:Prediction of terrestrial and extra-terrestrial parameters by modelling andextrapolating their natural regularities.Mausam, 52, 117-132.

Singh, N., and Sontakke, N.A. 1999: Onthe variability and prediction of rainfall inthe post monsoon season over India.International Journal of Climate, 19, 309-339.

Singh, N., and Sontakke, N.A. 2002: Onclimatic fluctuations and environmentalchanges of the Indo-Gangetic plains,India. Climatic Change, 52, 287-313.

Singh, O.P. 1998: Thermodynamicalcharacteristics of monsoon troposphereover the Bay of Bengal. Mausam, 50, 251-256.

Singh, O.P. 1998: The association betweenthe North Indian Ocean and summermonsoon rainfall over India. Mausam, 49,325-330.

Singh, O.P. 2001: Cause-effectrelationship between sea surfacetemperature, precipitation and sea levelalong the Bangladesh coast. Theoreticaland Applied Climatology, 68, 223-243.

Singh, O.P. 2001: Long term trends in thefrequency of monsoonal disturbances overthe North Indian Ocean. Mausam, 52, 655-658.

Singh, O.P. 2001: Multivariate ENSOindex and Indian monsoon rainfallrelationships on monthly and subdivisional scales. Meteorology andAtmospheric Physics, 78, 1-9.

Singh, O.P. 2002: Interannual variabilityand predictability of sea level along theIndian Coast. Theoretical and AppliedClimatology, 72, 11-28

Singh, O.P., Khan, T.M.A. and Rahman,M.S. 2001: Has the frequency of intensetropical cyclones increased in the NorthIndian Ocean? Current Science, 80, 575-580.

Singh, O.P., Khan, T.M.A. and Rahman,M.S. 2001: Probable reasons for enhancedcyclogenesis in the Bay of Bengal duringJuly – August of ENSO years. Global andPlanetary change, 29, 135-147.

Singh, O.P., Khan, T.M.A. and Rahman,M.S. 2001: Tropical cyclone frequencyover the North Indian Ocean in relation toSouthern Oscillation phenomenon.Mausam, 52, 511-514.

Singh, O.P., Khan, T.M.A., and Rahman,M.S. 2000: Changes in the frequency oftropical cyclones over the North IndianOcean. Meteorology and AtmosphericPhysics, 75, 11-20.

Singh, O.P., Khan, T.M.A., Rahman,M.S., and Salahuddin. 2000: Summermonsoon rainfall over Bangladesh inrelation to multivariate ENSO Index.Mausam, 51, 255-260.

Singh, R.P., Singh, D.K., Singh, A.K.,Hamar, D. and Lichtenberger, J. 1999:Application of matched filttering andparameter estimation technique to lowlatitude whistlers Journal of AtmosphericSolar and Terrestrial Physics, 61, 1081-1092.

Singh, S., Mahajan, K.K., Chodhary, andNagpal, O.P. 1999: Detection of Kelvin-Helmholtz instability with the Indian MSTradar – A case study. Journal ofGeophysical Research, 104, 3937-3945,

Sinha Ray, K.C., and Shewale, M.P. 2001:Probability of occurrence of drought invarious subdivisions of India. Mausam,52, 541-546.

Sinha Ray, K.C., and Srivastava, A.K.2000: Is there any change in extremeevents like drought and heavy rainfall?Current Science, 79, 155-158.

Sinha, S., and Pillai, J.S. 2001: Evaluationof moisture flux and relative humidity inthe surface layer from sonic anemometerdata. Journal of Agrometeorology, 3, 143-147.

Sivaramakrishnan, T.R., Prasad, J.R.1999: Some aerological observationsduring the passage of a cyclone. Mausam,50, 215-217.

Sontakke, N.A., Shea, D.J, Madden, R.A.,and Katz, R.W. 2001: Potential for long-range regional precipitation predictionover India. Mausam, 52, 47-56.

Sridharan, S., Muthuchami, A.,Ramakrishnan, B. 2000: Climatology ofcyclonic disturbances over Andaman andNicobar Islands. Mausam, 51, 96-100.

Sridharan, S., Muthuchami, A.,Ramakrishnan, B. 2000: Climatology ofcyclonic disturbances in the Arabian Sea.Mausam, 51,179-184.

Srinivasan, J. 2001: A simplethermodynamics model for seasonalvariation of monsoon rainfall. CurrentScience, 80, 73-77.

Srinivasan, J. and Gadgil, Sulochana.2002: On the Asian Brown cloudcontroversy. Current Science, 83, 1307-1309.

Srinivasan, J., and Gadgil, S. 2002: AsianBrown Cloud-fact and fantasy. CurrentScience, 83, 586-592.

Srivastava, A.K., and Sinha Ray, K.C.1999: Role of CAPE and CINE inmodulating the convective activitiesduring April over India. Mausam, 50,257-262.

Srivastava, A.K., and Sinha Ray, K.C.2000: Assessing peak warming of SSTover equatorial east Pacific Ocean (Nino 3

region) with the help of circulation patternover India during El-Nino events. Journalof Meteorological Society of Japan, 78,279-288.

Srivastava, A.K., and Sinha Ray, K.C.2000: Prediction of SST anomalies of eastPacific Ocean (NINO-3 region) using astatistical model. Journal of Theoreticaland Applied Climatology, 66,131-138.

Srivastava, A.K., Sinha Ray, K.C., andDe, U.S. 2000: Trends in the frequency ofcyclonic disturbances and theirintensification over Indian Seas. Mausam,51,113-118.

Srivastava, A.K., Sinha Ray, K.C., andRuta Kulkarni. 2002: Seasonal variationtrend in the tropopause height/temperatureover Indian stations and its modulation bySST anomalies of East Pacific Ocean.Mausam, 53, 439-446.

Srivastava, A.K., Sinha Ray, K.C., andYadav R.V. 2001: Is summer becomingmore uncomfortable over major cities ofIndia? Current Science, 81, 343-344.

Stephenson, D.B., Douville, H., and RupaKumar, K. 2001: Searching for afingerprint of global warming in the Asiansummer monsoon. Mausam, 52, 213-220.

Stephenson, D.B., Rupakumar, K.,Doblas-Reyes, F.J., Royer, J.F., Chauvin,F. and Pezzulli, S. 1999: Extreme dailyrainfall event and their impact onensemble forecasts of the Indian monsoon.Monthly Weather Review, 127, 1954-1966.

Suresh R. 1998: Determination of FractalDimension of Chaotic Attractor forMaximum Temperature over Madras.Mausam, 49, 167-172.

Suresh, R. 1999: Prediction of weatherparameters for aviation flight planning.Earth and Planet Sciences, 108, 277-286.

Suresh , R. 2000: A s implethermodynamical model to estimate the

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Suresh, R., Chandra, K.S., andSivagnanam, N. 2000: On applicability offrontier regression to nowcast surfacemeteorological parameters at Chennai andTrichy airports in Tamil Nadu. Mausam,51, 319-328.

Suresh, R., and Raj, Y.E.A. 2001: Someaspects of Indian northeast monsoon asderived from TOVS data. Mausam, 52,727-732.

Suresh, R., and Rengarajan, S. 2002: Onforecasting cyclone movement usingTOVS Data. Mausam, 53, 215-224.

Suresh, R., Sankaran, P.V., andRengarajan, S. 2002: Atmosphericboundary layer during northeast monsoonover Tamil Nadu and neighbourhood – Astudy using TOVS Data. Mausam, 53, 75-86.

Thamban, M., Rao, V.C., and Schneider,R.R. 2002: Reconstruction of latequaternary monsoon oscillations based onclay mineral proxies using sediment coresfrom the western margin of india. MarineGeology, 186, 527-539.

Thapliyal V. 2001: Long Range Forecastof summer monsoon rainfall over India:Evaluation and development of a newpower transfer model. Proceeding ofIndian National Science Academy, Part A(Physical Sciences), 67A, 343-359.

Thapliyal, V., Rajeevan, M., and Patil,S.R. 1998: Relationship between IndianSummer Monsoon Rainfall and SeaSurface Temperature anomalies overEquatorial Central and Eastern Pacific.Mausam 49, 229-234.

Thomas, B., Kasture, S.V., and Satyan, V.2000: Links between tropical SSTanomalies and precursory signalsassociated with the interannual variabilityof Asian summer monsoon. Meteorologyand Atmospheric Physics, 75, 39-49.

Thomas, B., Kasture, S.V., and Satyan, V.2000: Sensitivity of Asian summermonsoon and tropical circulations to 1987and 1988 sea surface temperatureanomalies. Atmosfera, 13, 147-166.

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Trivedi, D.K., Sanjay, J., and Singh, S.S.2002: Numerical simulation of a supercyclonic storm, Orissa 1999: impact ofinitial conditions. MeteorologicalApplication, 9, 367-376.

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PHYSICS AND CHEMISTRY OF THE OCEANS

E.DesaNational Institute of Oceanography, Goa-403 004

Introduction

Studies in the Physical and Chemicaloceanography in India encompass all aspectsof the disciplines. Over 150 organizationsparticipate in the studies. These could beviewed by way of their research outputs inthe form of publications.

In all, 276 Indian publications (listenclosed), during the period 1998-2002, onthe above mentioned disciplines were

downloaded from IndOcean: A database ofabstracts (compiled at NICMAS, NationalInstitute of Oceanography, Goa, India). Thebreak-up of these is as follows. It needs tobe mentioned that many of them aremultidisciplinary and an effort has beenmade to class them in only one mostrelevant category. The ASFA (AquaticSciences and Fisheries Abstracts) scheme ofcategorization has been used.

Topic No of items Progressivetotal

Physics: General 4Regional Studies 6TSD distribution, Water masses 15Air-water boundary layer 23Ocean circulation & currents 35Benthic boundary layer 2Tides, surges and sea level 26Wind waves 10Near shore dynamics 8Ocean acoustics 3Ocean optics 7 139Physics and chemistry of water 8Composition of water 37Organic compounds 12Chemistry of suspended matter 4Geochemistry of sediments 41Atmospheric chemistry 35 137Total 276 276

Almost equal number of references havebeen published in both the major disciplines(physical and chemical oceanography) underana lys i s . Among the Phys ica lOceanography, the significant number ofcontributions are in the areas such as: TSDdistribution, water masses; Air-waterboundary layer; Ocean circulation andcurrents; Tides, surges and sea level; andWind waves. Whereas in Chemical

Oceanography, the Composition of water;Organic compounds; Geochemistry ofsediments; and Atmospheric chemistry takefront seat. The mission oriented projectsacted as catalyst in increasing the number ofresearch contributions. The JGOFS,BOBMEX, INDOEX, etc., are some of suchexamples during the period of analysis.

The work was carried out in manyorganizations. The prominent ones(alphabetical order) are: Andhra University,Annamalai University, Centre for EarthScience Studies, Cochin University,Geological Survey of India, Indian Instituteof Science, Indian Institute of TechnologyDelhi, Indian Institute of TropicalMeteorology, National Centre for MediumRange Weather Forecasting, NationalGeophysical Research Institute, NationalInstitute of Oceanography, PhysicalResearch Laboratory, Space ApplicationsCentre, Vikram Sarabhai Space Centre. Ofthese National Institute of Oceanography atGoa alone had about 100 contributions.

For the items listed in the report or theIndOcean: A database of abstracts to viewother research contributions in thisg e o g r a p h i c a r e a , c o n t a c t :murari@darya.nio.org

Physics of the OceansGeneral

1. Fernandes, A.A.; Pednekar, S.;Vethamony, P. (NIO. Dona Paula,Goa 403 04, India). Inter-comparison between Aanderaa andPotok current meters deployedduring INDEX programme. 3.ISOPE (1999) Ocean MiningSymp.. Goa (India), 8-10 Nov 1999.The Proceedings of the Third (1999)ISOPE Ocean Mining Symposium,Goa, India, 1999. Chung, J.S.;Sharma, R. eds. InternationalSociety of Offshore and PolarEngineers. Cupertino, CA (USA).1999. 169-176.

2. Mitra, A.P. (National PhysicalLaboratory. New Delhi 110 012,Ind ia ) . INDOEX ( Ind ia ) :Introductory note. Curr. Sci. 76.1999. 886-889.

3. Pandey, P.C.; Gairola, R.M.(Antarctic Study Centre. Vasco-da-Gama, Goa 403 804, India). Satelliteoceanography: Review of theprogress and future prospects. Proc.

Indian Natl. Sci. Acad. (A Phys.Sci.). 66. 2000. 317-365.

4. Tyagi, R.N. (ISRO Satellite Centre.Bangalore 560 017, India). IRS-P4mission. Curr. Sci. 77. 1999. 1033-1037.

Regional Studies

5. Banerjee, R.K.; Pandit, P.K.;Chatterjee, S.K.; Das, B.B.;Sengupta, A. Chilka Lake - Presentand past. Central Inland CaptureFish. Research Inst.. Barrackpore,India. 1998. 89 pp.

6. Bruce, J.G.; Kindle, J.C.; Kantha,L.H.; Kerling, J.L.; Bailey, J.F.(Stennis Space Center; NavalOceanographic Office. Mississippi,USA). Recent observations andmodelling in the Arabian SeaLaccadive high region. J. Geophys.Res. (C: Oceans). 103. 1998. 7593-7600.

7. Pankajakshan, T.; Ghosh, A.K.;Muraleedharan, P.M. (NIO. DonaPaula, Goa 403 004, India). Anevaluation of XBT depth equationsfor the Indian Ocean. Deep-Sea Res.(I: Oceanogr. Res. Pap.). 45. 1998.819-827.

8. Sinha, P.C.; Rao, Y.R.; Dube, S.K.;Murthy, C.R.; Chatterjee, A.K.(Indian Institute of Technology;Centre for Atmospheric Sciences.New Delhi 110 016, India).Application of two turbulenceclosure schemes in the modelling oftidal currents and salinity in theHooghly Estuary. Estuar. Coast.Shelf Sci. 48. 1999. 649-663.

9. Srinivasan, J. (Indian Institute ofScience. Bangalore 560 012,Karnataka, India). Oceans andtropical climate. Semin. on PresentTrends and Future Directions inOcean Science. New Delhi (India),6-7 Oct 1997. Ocean science:Trends and future directions.

Somayajulu, B.L.K. ed. IndianNational Science Academy. NewDelhi (India). 1999. 53-86.

10. Vaz, G.G.; Vijaykumar, P.(Geological Survey of India; EastCoast Operations, II, Marine Wing.4 1 , K i r l a m p u d i L a y o u t ,Visakhapatnam 530 017, India).Occurrence of upper Oligocene -lower Miocene rocks in the uppercontinental slope, off the southernpart of Cauvery Basin. J. Geol. Soc.India. 57. 2001. 141-147.

TSD Distribution and water masses

11. Ballukraya, P.N.; Ravi, R.(University of Madras; Departmentof Applied Geology. Chennai 600025, India). Natural fresh-waterridge as barrier against sea-waterintrusion in Chennai city. J. Geol.Soc. India. 52. 1998. 279-286.

12. Jyothi, D.; Murty, T.V.R.; Sarma,V.V.; Rao, D.P. (NIO. RegionalCentre. 176 Lawson's Bay Colony,Visakhapatnam 530 017, A.P.,India). Computation of diffusioncoefficients for waters of GautamiGodavari estuary using one-dimensional advection-diffusionmodel. Indian J. Mar. Sci. 29. 2000.185-187.

13. Murty, V.S.N.; RameshBabu, V.;Rao, L.V.G.; Prabhu, C.V.; Tilvi, V.(NIO. Dona Paula, Goa 403 004,India). Diurnal variability of upperocean temperature and heat budgetin the southern Bay of Bengalduring October-November, 1998(BOBMEX-Pilot). Proc. IndianAcad. Sci. (Earth Planet. Sci.). 109.2000. 267-277.

14. Murty, V.S.N.; Gupta, G.V.M.;Sarma, V.V.; Rao, B.P.; Jyothi, D.;Shastri, P.N.M.; Supraveena, Y.(NIO. Dona Paula, Goa 403 004,India). Effect of vertical stabilityand circulation on the depth of thechlorophyll maximum in the Bay of

Bengal during May-June, 1996.Deep-Sea Res. (I: Oceanogr. Res.Pap.). 47. 2000. 859-873.

15. Nayar, S.; Gowda, G.; Gupta,T.R.C. (University of AgriculturalSciences Bangalore; College ofFisheries. Mangalore 575 002,Karnataka, India). Spatial andt e m p o r a l v a r i a t i o n s i nhydrographical parameters inTalapady lagoon, southwest coast ofIndia. Indian J. Mar. Sci. 29. 2000.77-79.

16. Prasad, T.G.; Ikeda, M.;PrasannaKumar, S. (GraduateSchool of Environmental EarthScience; Division of Ocean andAtmospheric Sciences. Sapporo,Japan). Seasonal spreading of thePersian Gulf water mass in theArabian Sea. J. Geophys. Res. (C:Oceans). 106. 2001. 17059-17071.

17. PrasannaKumar, S.; Prasad, T.G.(NIO. Dona Paula, Goa 403 004,India). Formation and spreading ofArabian Sea high-salinity watermass. J. Geophys. Res. (C: Oceans).104. 1999. 1455-1464.

18. RameshBabu, V.; Murty, V.S.N.;Suryanarayana, A.; Beena, B.S.;Niranjan, K, (NIO. Dona Paula, Goa403 004, India). Watermassstructure at benthic disturbance site(INDEX area) and anticipatedmining effects on hydro-physicalproperties. 3. ISOPE (1999) OceanMining Symp.. Goa (India), 8-10Nov 1999. The Proceedings of theThird (1999) ISOPE Ocean MiningSymposium, Goa, India, 1999.Chung, J.S.; Sharma, R. eds.International Society of Offshoreand Polar Engineers. Cupertino, CA(USA). 1999. 208-215.

19. Rao, R.R.; Sivakumar, R. (NavalPhysical and OceanographicLaboratory. Cochin, India).Seasonal variability of near-surfacethermal structure and heat budget of

the mixed layer of the tropicalIndian Ocean from a new globalocean temperature climatology. J.Geophys. Res. (C: Oceans). 105.2000. 995-1015.

20. Rao, T.V.N. (NIO; Regional Centre.176 Lawson's Bay Colony,Visakhapatnam 530 017, India).Time-dependent stratification in theGauthami-Godavari Estuary.Estuaries. 24. 2001. 18-29.

21. Rao, Y.R.; Sinha, P.C.; Dube, S.K.(National Institute of Technology.IC&SR Building, IIT Campus,Madras 600 036, India). Circulationand salinity in Hooghly Estuary: Anumerical study. Indian J. Mar. Sci.27. 1998. 121-128.

22. Sarma, Y.V.B.; Rao, E.P.R.; Saji,P.K.; Sarma, V.V.S.S. (NIO. DonaPaula, Goa 403 004, India).Hydrography and circulation of theBay of Bengal during withdrawalphase of the southwest monsoon.Oceanol. Acta. 22. 1999. 453-471.

23. Shetye, S.R.; Gouveia, A.D. (NIO.Dona Paula, Goa 403 004, India).Coastal circulation in the NorthIndian Ocean: Coastal segment(14,S-W). The global coastal ocean:Regional studies and syntheses.Robinson, A.R.; Brink, K.H. eds.John Wiley & Sons. New York,USA. 11. 1998. 523-556. (The Sea:Ideas and Observations in the Studyof the Seas)

24. Subramanian, B.; Mahadevan, A.(University of Madras; CAS inBotany. Madras 600 025, India).Seasonal and diurnal variation ofhydrobiological characters ofcoastal water of Chennai (Madras),Bay of Bengal. Indian J. Mar. Sci.28. 1999. 429-433.

25. Sudhakar, A.C.; Ramesha, T.J.;Lakshmipathi, M.T.; Hariharan, V.(Universi ty of AgriculturalSciences; College of Fisheries.

Mangalore 575 002, India).Hydrographic and nutrient profile ofthe interstitial waters at selectedbeaches of Mangalore. Environ.Ecol. 18. 2000. 675-680.

Air-water boundary layer

26. Ali, M.M.; Sharma, R. (SpaceApplications Centre; OceanicScience Division. Ahmedabad 380053, India). Remote sensing of themarine mixed layer. Indian J. Mar.Sci. 27. 1998. 26-29.

27. Asharaf, T.T.M.; Nair, R.P.;Sanjana, M.C.; Muraleedharan, G.;Kurup, P.G. (NIO; Regional Centre.Cochin 682 014, India). Surfacewave statistics and spectra forValiathura coastlines, SW coast ofIndia. Indian J. Mar. Sci. 30. 2001.9-17.

28. Basu, S. (National Centre forM e d i u m R a n g e W e a t h e rForecasting. Mausam BhavanComplex, Lodi Road, New Delhi110 003, India). Impact ofboundary-layer parameterization insimulating the marine boundarylayer for INDOEX. Curr. Sci. 76.1999. 907-911.

29. Basu, S. (National Centre forMarine Range Weather Forecasting.INSAT Building, Mausam BhavanComplex, Lodi Road, New Delhi,India). Marine boundary layersimulation and verification duringBOBMEX-Pilot NCMRWF model.Proc. Indian Acad. Sci. (EarthPlanet. Sci.). 109. 2000. 285-292.

30. Basu, S . ; Pal iwal , R.K. ;Satyanarayana, A.N.V.; Mohanty,U.C.; Lykossov, V.N.; Sam, N.V.(National Centre for Medium RangeWeather Forecasting. MausamBhavan Complex, Lodi Road, NewDelhi 110 003, India). Acomparative analysis of thecharacteristics of the marineboundary layer with GCM and 1-D

PBL model simulations usingINDOEX IFP-99 data. Curr. Sci. 80.2001. 55-59.

31. Bhat, G.S.; Ameenulla, S.;Venkataramana, M.; Sengupta, K.(Indian Institute of Science; Centrefor Atmospheric and OceanSciences. Bangalore 560 012,India). Atmospheric boundary layercharac ter i s t ics dur ing theBOBMEX-Pilot experiment. Proc.Indian Acad. Sci. (Earth Planet.Sci.). 109. 2000. 229-237.

32. Gupta, K.S.; Ramachandran, R.(Vikram Sarabhai Space Centre;Space Physics Laboratory.Trivandrum 695 022, India).Tropical atmospheric boundarylayer. Proc. Indian Natl. Sci. Acad.(A: Phys. Sci.). 64. 1998. 267-276.

33. Joseph, A.; Desa, J.A.E.; Foden, P.;Taylor, K.; McKeown, J.; Desa,Ehrlich. (NIO. Dona Paula, Goa 403004, India). Evaluation andperformance enhancement of apressure transducer under flows,waves, and a combination of flowsand waves. J. Atmos. Ocean.Technol. 17. 2000. 357-365.

34. Krishnamurthy, V.; Shukla, J. (Inst.of Global Environment and Society;Center for Ocean-Land-AtmosphereStud.. 4041 Powder Mill Road,Suite 302, Calverton, MD 20705,USA). Observed and modelsimulated interannual variability ofthe Indian monsoon. Mausam. 52.2001. 133-150.

35. Kumar, B.P.; Kalra, R.; Dube, S.K.;Sinha, P.C.; Rao, A.D.; Kumar, R.;Sarkar, A. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. New Delhi,India). Extreme wave conditionsover the Bay of Bengal duringsevere cyclone - Simulationexperiment with two spectral wavemodels. Mar. Geod. 23. 2000. 91-102.

36. Mahajan, P.N.; Chinthalu, G.R.;Rajamani, S. (Indian Institute ofTropical Meteorology. Pune 411008, India). Use of satellite data forradiative energy budget study ofIndian summer monsoon. Proc.Indian Acad. Sci. (Earth Planet.Sci.). 107. 1998. 19-32.

37. Ramana, M.V.; Gupta, K.S.;Ramachandran, R.; Ravindran, S.;Ameenulla, S.; Raju, J.V.S. (VikramSarabhai Space Centre; SpaceP h y s i c s L a b o r a t o r y .Thiruvananthapuram 695 022,India). Latitude variation ofboundary layer height over IndianOcean during pre- and First FieldPhast (FFP-98) of INDOEX. Curr.Sci. 76. 1999. 898-902.

38. Rao, A.D.; Dube, S.K. (IndianInstitute of Technology Delhi. NewDelhi 110 016, India). Interannualvariability of turbulent heat flux andSST over the Indian Ocean. 8. Natl.Symp., TROPMET-99. RegionalMeteorological Centre, Chennai(India) , 16-19 Feb 1999.Meteorology beyond 2000.P r o c e e d i n g s o f N a t i o n a lSymposium, TROPMET-99, 16-19February 1999. Bhatnagar, A.K.;Raghavan, S.; Keshavamurthy,R . N . ; G a n e s a n , G . S . ;S h a n m u g a s u n d a r a m , J . ;Rajarathnam, S.; Jayanthi, N.;Subramanian, S.K.; Suresh, R.; Raj,Y.E.A. eds. India MeteorologicalSociety. Chennai (India). 1999. 537-545.

39. Rao, E.P.R.; RameshBabu, V.; Rao,L.V.G. (NIO. Dona Paula, Goa 403004, India). Heat content variabilityin the tropical Indian Ocean duringsecond pre-INDOEX campaign(boreal winter 1996-1997). Curr.Sci. 76. 1999. 1001-1004.

40. Rao, R.R.; Sivakumar, R. (NPOL.Kochi 682 021, India). Observedseasonal variability of heat content

in the upper layers of the tropicalIndian Ocean from a new globalocean temperature climatology.Deep-Sea Res. (I: Oceanogr. Res.Pap.). 45. 1998. 67-89.

41. Reddy, K.G.; Ram, P.S. (AndhraUnivers i ty; Department ofMeteorology and Oceanography.Visakhapatnam 530 003, India).BOBMEX-98 Pilot: Measurementand analysis of incoming shortwaveradiation data. Proc. Indian Acad.Sci. (Earth Planet. Sci.). 109. 2000.249-254.

42. Sam, N.V.; Mohanty, U.C.;Satyanarayana, A.N.V. (IndianInstitute of Technology; Centre forAtmospheric Sciences. New Delhi,India). Conserved variable analysisof the marine boundary layer andair-sea exchange processes usingBOBMEX-Pilot data sets. Proc.Indian Acad. Sci. (Earth Planet.Sci.). 109. 2000. 305-314.

43. Sathe, P.V.; Muraleedharan, P.M.(NIO. Dona Paula, Goa 403 004,India). Retrieval of sea surface airtemperature from satellite data overIndian Ocean: An empiricalapproach. Asian Meteorol. OnlineNewsl. (AMON). 3. 1999. 1-7.

44. Satyanarayana, A.N.V.; Mohanty,U.C.; Sam, N.V. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. New Delhi110 016, India). A study on thecharacteristics of the marineboundary layer over Indian withORV Sagar Kanya cruise 120during 1997. Curr. Sci. 76. 1999.890-897.

45. Satyanarayana, A.N.V.; Mohanty,U.C.; Sam, N.V.; Basu, S.; Lyla,P.S. (Indian Institute of TechnologyDelhi; Centre for AtmosphericSciences. New Delhi, India).Numerical simulation of the marineboundary layer characteristics overthe Bay of Bengal as revealed by

BOBMEX-98 Pilot experiment.Proc. Indian Acad. Sci. (EarthPlanet. Sci.). 109. 2000. 293-303.

46. Satyanarayana, A.N.V.; Mohanty,U.C.; Niyogi, D.S.; Raman, S.;Lykossov, V.N.; Warrior, H.; Sam,N.V. (Indian Inst i tute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. New Delhi110 016, India). A study on marineboundary layer processes in theITCZ and non-ITCZ regimes overIndian Ocean with INDOEX IFP-99data. Curr. Sci. 80. 2001. 39-45.

47. Singh, O.P. (Meteorological Centre.Bhubaneswar, India). Multiplevariability of summer sea surfacetemperature (SST) and evaporationover the Indian Seas. Mausam. 50.1999. 335-342.

48. Wajsowicz, R.C.; Schopf, P.S.(University of Maryland at CollegePark; Department of Meteorology.College Park, Maryland). Oceanicinfluences on the seasonal cycle inevaporation over the Indian Ocean.J. Clim. 14. 2001. 1199-1226.

Ocean circulation and currents

49. Anilkumar, N.; Revichandran, C.;Sankaranarayanan, V.N.; Josanto,V. (NIO; Regional Centre. P.B. No.1913, Cochin 682 018, India).Residual fluxes of water, salt andsuspended sediment in the BeyporeEstuary. Indian J. Mar. Sci. 27.1998. 157-162.

50. Behera, S.K.; Salvekar, P.S.; Ganer,D.W.; Deo, A.A. (Indian Institute ofTropical Meteorology. Pune 411008, India). Interannual variabilityin simulated circulation along eastcoast of India. Indian J. Mar. Sci.27. 1998. 115-120.

51. Behera, S.K.; Salvekar, P.S. (IndianInstitute of Tropical Meteorology.Pune 411 008, India). Numericalinvestigation of coastal circulation

around India. Mausam. 49. 1998.345-360.

52. Chakraborty, A.; Upadyayaya, H.C.;Sharma, O.P. (Mody College ofEngineering and Technology.Lakshmangarh 332 311, Sikar,Rajasthan, India). Interannualvariabil i ty of sea surfacetemperatures in ocean generalcirculation model. Indian J. Mar.Sci. 29. 2000. 96-105.

53. Chakraborty, A.; Upadyayaya, H.C.;Sharma, O.P. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. New Delhi110 016, India). Response of anocean general circulation model towind and thermodynamic forcings.Proc. Indian Acad. Sci. (EarthPlanet. Sci.). 109. 2000. 329-337.

54. Gairola, R.M. (Space ApplicationsCentre, ISRO; Oceanic SciencesDivision. Ahmedabad 380 053,India). A study of currents and sealevel variability over Indian Oceanby TOPEX/POSEIDON altimeter.ISRS Natl. Symp. on RemoteSensing Applications for NaturalResources: Retrospective andPerspective. Bangalore (India), 19-21 Jan 1999. Proceedings of ISRSNational Symposium on RemoteSensing Applications for NaturalResources: Retrospective andPerspective, January 19-21, 1999,Bangalore. Adiga, S.; Hegde, V.S.;Ranganath, B.K.; Manavalan, P.;Diwakar, P.G.; Gowda, H.H.;Krishnamurthy, J.; Srivastava, S.K.;Raj, U.; Bandyopadhyay, S.;Thomas, J.V.; Gowrisankar, D. eds.Indian Society of Remote Sensing(ISRS). Bangalore (India). 2000.441-446.

55. Gairola, R.M.; Basu, S.; Pandey,P.C. (Space Applications Centre;Oceanic Sciences Division.Ahmedabad 380 015, India). Eddydetection over southern IndianOcean using TOPEX/POSEIDON

altimeter data. Mar. Geod. 24. 2001.107-121.

56. Gopalan, A.K.S.; GopalaKrishna,V.V.; Ali, M.M.; Sharma, R. (SpaceApplications Centre. SAC P.O.,Ahmedabad 380 053, India. NIO).Detection of Bay of Bengal eddiesfrom TOPEX and in situobservations. J. Mar. Res. 58. 2000.721-734.

57. Iyengar, G.R.; Ramesh, K.J.;Paliwal, R.K.; Madan, O.P.(National Centre for Medium RangeWeather Forecasting. INSATBuilding Annexe, Mausam BhavanComplex, Lodi Road, New Delhi110 003, India). Structuralcharacteristics of the Inter TropicalConvergence Zone over theequatorial Indian Ocean duringINDOEX-1999 f ie ld phaseexperiment. Curr. Sci. 80. 2001. 18-24.

58. Joseph, B.; Swathi, P.S. (CSIRCentre for Mathematical Modellingand Computer Simulat ion.Bangalore, India). Lagrangianparticle transport in the IndianOcean: A model study. J. Geophys.Res. (C: Oceans). 104. 1999. 5211-5224.

59. Kumar, P.V.H.; Rao, C.V.K.P.;Swain, J.; Madhusoodanan, P.(Naval Physical and OceanographicLaboratory. Thrikkakara, Kochi 682021, India) . Intra-seasonaloscillations in the central Bay ofBengal during summer monsoon1999. Curr. Sci. 80. 2001. 786-790.

60. Murty, V.S.N.; RameshBabu, V.;Suryanarayana, A.; Beena, B.S.(NIO. Dona Paula, Goa 403 004,India). Current structure and kineticenergy of the abyssal waters in theCentral Indian Ocean Basin. 3.ISOPE (1999) Ocean MiningSymp.. Goa (India), 8-10 Nov 1999.The Proceedings of the Third (1999)ISOPE Ocean Mining Symposium,

Goa, India, 1999. Chung, J.S.;Sharma, R. eds. InternationalSociety of Offshore and PolarEngineers. Cupertino, CA (USA).1999. 216-226.

61. Murty, V.S.N.; Sarma, M.S.S.;Lambata, B.P.; Gopalakrishna,V.V.; Pednekar, S.M.; Rao, A.S.;Luis, A.J.; Kaka, A.R.; Rao, L.V.G.(NIO. Dona Paula, Goa 403 004,India). Seasonal variability ofupper-layer geostrophic transport inthe tropical Indian Ocean during1992-1996 along TOGA-I XBTtracklines. Deep-Sea Res. (I:Oceanogr. Res. Pap.). 47. 2000.1569-1582.

62. Murty, V.S.N.; Savin, M.;RameshBabu, V.; Suryanarayana,A. (NIO. Dona Paula, Goa 403 004,India). Seasonal variability in thevertical current structure and kineticenergy in the Central Indian OceanBasin. Deep-Sea Res. (II: Top. Stud.Oceanogr. 48. 2001. 3309-3326.

63. Naidu, P.D.; RameshKumar, M.R.;RameshBabu, V. (NIO. Dona Paula,Goa 403 004, India). Time andspace variations of monsoonalupwelling along the west and eastcoasts of India. Cont. Shelf Res. 19.1999. 559-572.

64. Pal, P.K.; Ali, M.M. (SpaceApplications Centre. Ahmedabad380 053, India). Arabian Sea eddiessimulated by an ocean model withthermodynamics. Indian J. Mar. Sci.27. 1998. 72-75.

65. Peter, B.N.; Mizuno, K. (CochinUniversity of Science andTechnology; Dept. of PhysicalOceanography, School of MarineSciences. Fine Arts Ave, Cochin682 016, India). Annual cycle ofsteric height in the Indian Oceanestimated from the thermal field.Deep-Sea Res. (I: Oceanogr. Res.Pap.). 47. 2000. 1351-1368.

66. Pillai, V.N.; Singh, V.V.; Kumar,P.K.; Kumar, A.N. (Central MarineFisheries Research Institute (ICAR).P.O. Box No. 1603, Tatapuram P.O.Cochin 14, India). Presence ofupwelled water in the shelf regionalong the central east coast of Indiatowards the end of summermonsoon and its possible effect onthe migration of Bullseye(Priacanthus spp.) in to theshallower areas of the shelf. 4.Indian Fisheries Forum. Kochi,Kerala, 24-28 Nov 1996. The FourthI n d i a n F i s h e r i e s F o r u m ,Proceedings. 24-28 November,1996, Kochi, Kerala. Joseph, M.M.;Menon, N.R.; Nair, N.U. eds. AsianFisheries Society, Indian Branch.Mangalore (India). 1999. 81-82.

67. PrasannaKumar, S.; Ramaiah, N.;Gauns, M.; Sarma, V.V.S.S.;Muraleedharan, P.M.; Raghukumar,S.; DileepKumar, M.; Madhupratap,M. (NIO. Dona Paula, Goa 403 004,India). Physical forcing ofbiological productivity in thenorthern Arabian Sea during thenortheast monsoon. Deep-Sea Res.(II: Top. Stud. Oceanogr.). 48. 2001.1115-1126.

68. RameshBabu, V.; Murty, V.S.N.;Rao, L.V.G.; Prabhu, C.V.; Tilvi, V.(NIO. Dona Paula, Goa 403 004,India). Thermohaline structure andcirculation in the upper layers of thesouthern Bay of Bengal duringB O B M E X - P i l o t ( O c t o b e r -November 1998). Proc. IndianAcad. Sci. (Earth Planet. Sci.). 109.2000. 255-265.

69. RameshBabu, V.; Suryanarayana,A.; Murty, V.S.N. (NIO. DonaPaula, Goa 403 004, India).Thermohaline circulation in theCentral Indian Ocean Basin (CIB)during austral summer adn winterperiods of 1997. Deep-Sea Res. (II:Top. Stud. Oceanogr. 48. 2001.3327-3342.

70. Rao, A.D.; Dube, S.K. (IndianInstitute of Technology; Centre forAtmospheric Sciences. Hauz Khas,New Delhi 110 016, India). A three-dimensional simulation of coastalupwelling/downwelling off eastcoast of India. Indian J. Mar. Sci.27. 1998. 138-143.

71. Saji, P.K.; Shenoi, S.C.; Almeida,A.; Rao, L.V.G. (NIO. Dona Paula,Goa 403 004, India). Inertialcurrents in the Indian Ocean derivedfrom satellite tracked surfacedrifters. Oceanol. Acta. 23. 2000.635-640.

72. Sengupta, D.; Senan, R.; Goswami,B.N. (Indian Institute of Science;Centre for Atmospheric and OceanicSciences. Bangalore, India). Originof intraseasonal variability ofcirculation in the tropical centralIndian Ocean. Geophys. Res. Lett.28. 2001. 1267-1270.

73. Shaji, C.; Bahulayan, N.; Rao, A.D.;Dube, S.K. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. New Delhi110 016, India. NIO). Variousapproaches to the modelling of largescale 3-dimensional circulation inthe Ocean. Indian J. Mar. Sci. 27.1998. 104-114.

74. Shaji, C.; Bahulayan, N.; Dube,S.K.; Rao, A.D. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. Hauz Khas,New Delhi 110 016, India. NIO). Amulti-level adaptation model ofcirculation for the western IndianOcean. Int. J. Numer. MethodsFluids. 31. 1999. 1221-1264.

75. Sharma, R.; Gopalan, A.K.S.; Ali,M.M. (Space Applications Centre.Ahmedabad, India). Interannualvariation of eddy kinetic energyf r o m T O P E X a l t i m e t e robservations. Mar. Geod. 22. 1999.239-248.

76. Shenoi, S.S.C.; Saji, P.K.; Almeida,A.M. (NIO. Dona Paula, Goa 403004, India). Near-surface circulationand kinetic energy in the tropicalIndian Ocean derived fromlagrangian drifters. J. Mar. Res. 57.1999. 885-907.

77. Shetye, S.R. (NIO. Dona Paula, Goa403 004, India). West India coastalcur ren t and LakshadweepHigh/Low. Sadhana. 23. 1998. 637-651.

78. Shetye, S.R. (NIO. Dona Paula, Goa403 004, India). Dynamics ofcirculation of the waters aroundIndia. Semin. on Present Trends andFuture Directions in Ocean Science.New Delhi (India), 6-7 Oct 1997.Ocean science: Trends and futuredirections. Somayajulu, B.L.K. ed.Indian National Science Academy.New Delhi (India). 1999. 1-21.

79. Singh, G.P.; Chattopadhyay, J.(Banaras Hindu University; Dept. ofGeophysics. Varanasi 221 005,India). Influence of some circulationanomalies on Indian northeastmonsoon rainfall. Mausam. 49.1998. 443-448.

80. Subrahamanyam, D.B.; Gupta, K.S.;Ravindran, S.; Krishnan, P. (SpacePhysics Laboratory; VikramS a r a b h a i S p a c e C e n t r e .Thiruvananthapuram 695 022,India). Study of sea breeze and landbreeze along the west coast ofIndian sub-continent over thelatitude range 15~'N to 8~'N duringINDOEX IFP-99 (SK-141) cruise.Curr. Sci. 80. 2001. 85-88.

81. Tewari, K.; Kumar, R.; Gohil, B.S.;Basu, S. (Space Applications Centre(ISRO); Oceanic Sciences Division.Ahmedabad 380 053, India). Use ofERS-1 scatterometer and topexaltimeter data in a nonlinear reducedgravity model of the northwesternIndian Ocean. Indian J. Mar. Sci.29. 2000. 1-6.

82. Unnikrishnan, A.S.; Murty, V.S.N.;Babu, M.T.; Gopinathan, C.K.;Charyulu, R.J.K. (NIO. Dona Paula,Goa 403 004, India). Anomalouscurrent structure in the easternequatorial Indian Indian Oceanduring the south-west monsoon of1994. Mar. Freshwat. Res. 52. 2001.727-734.

83. Vinayachandran, P.N.; Masumoto,Y.; Mikawa, T.; Yamagata, T.(Institute for Global ChangeResearch; Frontier Research Systemfor Global Change. Tokyo, Japan).Intrusion of the Southwest MonsoonCurrent into the Bay of Bengal. J.Geophys. Res. (C: Oceans). 104.1999. 11077-11085.

Benthic boundary layer

84. Basu, S.; Gupta, M.D. (NationalCentre for Medium Range WeatherForecasting. Mausam BhavanComplex, Lodi Road, New Delhi110 003, India). Impact of INDOEXdata in the NCMRWF analysis-forecast system and evolution ofboundary layer structure during IFP-99. Curr. Sci. 80. 2001. 7-11.

85. Morwal, S.B. (Indian Institute ofTropical Meteorology. Pune 411008, India). Convective boundarylayer structure over the equatorialIndian oceanic region. Mausam. 51.2000. 169-176.

Tides, Surges and Sea level

86. Ali, M.M.; Sharma, R. (SpaceApplications Centre; Meteorologyand Oceanography Group.Ahmedabad, India). Studying IndianOcean typ ica l dynamica lphenomena us ing TOPEXobservations. Mar. Geod. 21. 1998.193-201.

87. Anon. Final report on the project sealevel variability in the coastal regionof India. Funded by Department of

Ocean Development during 1994-1999 under their SELMANprogramme. Natl . Inst . ofOceanography. Dona Paula, Goa(India). 2001. 22 pp.

88. Chittibabu, P.; Dube, S.K.; Sinha,P.C.; Rao, A.D. (Indian Institute ofTechnology. New Delhi 110 016,India). Storm surge prediction in thenorth Indian Ocean. 8. Natl. Symp.,T R O P M E T - 9 9 . R e g i o n a lMeteorological Centre, Chennai(India) , 16-19 Feb 1999.Meteorology beyond 2000.P r o c e e d i n g s o f N a t i o n a lSymposium, TROPMET-99, 16-19February 1999. Bhatnagar, A.K.;Raghavan, S.; Keshavamurthy,R . N . ; G a n e s a n , G . S . ;S h a n m u g a s u n d a r a m , J . ;Rajarathnam, S.; Jayanthi, N.;Subramanian, S.K.; Suresh, R.; Raj,Y.E.A. eds. India MeteorologicalSociety. Chennai (India). 1999. 552-556.

89. Chittibabu, P.; Dube, S.K.; Rao,A.D.; Sinha, P.C.; Murty, T.S.(Indian Institute of Technology;Centre for Atmospheric Sciences.New Delhi, India). Numericalsimulation of extreme sea levelsusing location specific highresolution model for Gujarat coastof India. Mar. Geod. 23. 2000. 133-142.

90. Govil, R.; Saxena, A. (BanasthaliVidyapith; Department of ComputerScience and Electronics. P.O.Banasthali, Dist. Tonk, Rajasthan,India). Compression of tidal data fordigital storage. Int. Semin. onQuaternary Sea-Level Variation,Shoreline Displacement and CoastalEnvironment. Tamil Nadu (India),[nd] . Proceedings of theInternational Seminar on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Rajamanickam, G.V.;Tooley, M.J. eds. New AcademicPubl.. Delhi (India). 2001. 128-131.

91. Joseph, A.; Vijayakumar; Desa,Elger; Desa, E.; Peshwe, V.B. (NIO.Dona Paula, Goa 403 004, India). Atechnique to circumvent lowerdensity water trapping by tide-wells.Natl. Symp. on Ocean Electronics.Cochin, India, 16-17 Dec 1999.SYMPOL-'99. Proceedings of theNational Symposium on OceanElectronics, 16-17 December, 1999.Cochin Univ. of Sci. and Technol..Cochin, India. 1999. 55-63.

92. Kumar, R.; Basu, S.; Pandey, P.C.(ISRO; Space Applications Centre,Oceanic Sciences Division.Ahmedabad 380 053, India).Variational data assimilation inocean model: A simulationexperiment. Indian J. Mar. Sci. 27.1998. 52-59.

93. Latha, G.; Mahadevan, R. (NationalInstitute of Ocean Technology. IITCampus, Madras 600 036, India).Sensitivity and predictive capabilitystudies on a finite element surgesimulation model. Indian J. Mar.Sci. 29. 2000. 89-95.

94. Mahadevan, R.; Latha, G. (NationalInstitute of Ocean Technology.Chennai 600 036, India). Influenceof coastal flooding on surgeestimates along the east coast ofIndia. Indian J. Mar. Sci. 30. 2001.115-122.

95. Paul, A.K. (Asutosh College;Departement of Geography.Calcutta, India). Cyclonic stormsand their impacts on West Bengalcoast. Int. Semin. on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Tamil Nadu (India),[nd] . Proceedings of theInternational Seminar on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Rajamanickam, G.V.;Tooley, M.J. eds. New AcademicPubl.. Delhi (India). 2001. 8-31.

96. Prasad, K.V.S.R. (AndhraUnivers i ty; Department ofMeteorology and Oceanography.Waltair, India). Sea level trends andconsequent impact on shorelinechanges. Int. Semin. on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Tamil Nadu (India),[nd] . Proceedings of theInternational Seminar on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Rajamanickam, G.V.;Tooley, M.J. eds. New AcademicPubl.. Delhi (India). 2001. 125-127.

97. PrasannaKumar, S.; Snaith, H.;Challenor, P.; Guymer, H.T. (NIO.Dona Paula, Goa 403 004, India).Seasonal and inter-annual seasurface height variations of thenorthern Indian Ocean from theTOPEX/POSEIDON altimeter.Indian J. Mar. Sci. 27. 1998. 10-16.

98. Shankar, D. Low-frequencyvariability of sea level along thecoast of India. Goa Univ.. India.Goa Univ.. Goa (India). Ph.D. 1998.226 pp.

99. Shankar, D.; Shetye, S.R. (NIO.Dona Paula, Goa 403 004, India).Are interdecadal sea level changesalong the Indian coast influenced byvariability of monsoon rainfall? J.Geophys. Res. (C: Oceans). 104.1999. 26031-26042.

100. Shankar, D. (NIO. Dona Paula, Goa403 004, India). Seasonal cycle ofsea level and currents along thecoast of India. Curr. Sci. 78. 2000.279-288.

101. Shankar, D.; Shetye, S.R. (NIO.Dona Paula, Goa 403 004, India).Why is mean sea level along theIndian coast higher in the Bay ofBengal than the Arabian Sea?Geophys. Res. Lett. 28. 2001. 563-565.

102. Shetye, S.R.; Gouveia, A.D.;Singbal, S.Y.S.; Naik, C.G.; Sundar,D.; Michael, G.S.; Nampoothiri, G.(NIO. Dona Paula, Goa 403 004,India). Propagation of tides in theMandovi-Zuari estuarine network.Integrated Coastal and Marine AreaManagement Project Directorate.Chennai (India), Dep. of OceanDevelopment. Workshop onIntegrated Coastal and Marine AreaManagement Plan for Goa. Dep. ofSc ience , Techno logy andEnvironment, Gov. of Goa, Saligao,Bardez, Goa, 25-26 Aug 1999.Proceedings of the Workshop onIntegrated Coastal and Marine AreaManagement Plan for Goa.ICMAM-PD. Chennai (India). 1999.174-193.

103. Shetye, S.R. (NIO. Dona Paula, Goa403 004, India). Propagation of tidesin the Mandovi and Zuari estuaries.Sadhana. 24. 1999. 5-16.

104. Shetye, S.R.; Gouveia, A.D.;Singbal, S.Y.S.; Naik, C.G.; Sundar,D.; Michael, G.S.; Nampoothiri, G.(NIO. Dona Paula, Goa 403 004,India). Propagation of tides in theMandovi-Zuari estuarine network.Integrated Coastal and Marine AreaManagement Project Directorate.Chennai (India). Dep. of OceanDevelopment. Workshop onIntegrated Coastal and Marine AreaManagement Plan for Goa. Dep. ofSc ience , Techno logy andEnvironment, Gov. of Goa, Saligao,Bardez, Goa, 25-26 Aug 1999.Proceedings of the Workshop onIntegrated Coastal and Marine AreaManagement Plan for Goa.ICMAM-PD. Chennai (India). 1999.174-193.

105. Shetye, S.R. (NIO. Dona Paula, Goa403 004, India). Tides in the Gulf ofKutch, India. Cont. Shelf Res. 19.1999. 1771-1782.

106. Singh, S.K.; Basu, S.; Kumar, R.;Agarwal, V.K. (Space ApplicationsCentre; Oceanic Sciences Division,Meteorology and OceanographyGroup. Ahmedabad, India). Impactof satellite altimetry on simulationsof sea level variability by an IndianOcean model. Mar. Geod. 24. 2001.53-63.

107. Sinha, P.C.; Dube, S.K.; Mitra,A.K.; Murty, T.S. (Indian Instituteof Technology; Centre forAtmospheric Sciences. New Delhi,India). A tidal flow model for theGulf of Kachchh, India. Mar. Geod.23. 2000. 117-132.

108. Subrahmanya, K.R. (JawaharlalNehru Centre for AdvancedScientific Research; GeodynamicsUnit. Jakkur, Bangalore 560 064,India). Relative fall in sea level inparts of southern Karnataka Coast.Curr. Sci. 75. 1998. 727-730.

109. Sundar, D.; Shankar, D.; Shetye,S.R. (NIO. Dona Paula, Goa 403004, India). Sea level during stormsurges as seen in tide-gauge recordsalong the east coast of India. Curr.Sci. 77. 1999. 1325-1332.

110. Unnikrishnan, A.S.; Gouveia, A.D.;Vethamony, P. (NIO. Dona Paula,Goa 403 004, India). Tidal regime inGulf of Kutch, west coast of India,by 2D model. J. Waterway PortCoast. Ocean Eng. 125. 1999. 276-284.

111. Unnikrishnan, A.S.; Shetye, S.R.;Michael, G.S. (NIO. Dona Paula,Goa 403 004, India). Tidalpropagation in the Gulf ofKhambhat, Bombay High, andsurrounding areas. Proc. IndianAcad. Sci. (Earth Planet. Sci.). 108.1999. 155-177.

Wind waves

112. Bawiskar, S.M.; Chipade, M.D.;Singh, S.S. (Indian Institute of

Tropical Meteorology. Pune 411008, India). Intra-seasonal variationsof kinetic energy of lowertropospheric zonal waves duringnorthern summer monsoon. Proc.Indian Acad. Sci. (Earth Planet.Sci.). 107. 1998. 121-126.

113. Deo, M.C.; Jha, A.; Chaphekar,A.S.; Ravikant, K. (Indian Instituteof Technology; Dept. of CivilEngineering. Bombay 400 076,India). Neural networks for waveforecasting. Ocean Eng. 28. 2001.889-898.

114. Fernandes, A.A.; Sarma, Y.V.B.;Menon, H.B. (NIO. Dona Paula,Goa 403 004, India). Directionalspectrum of ocean waves from arraymeasurements using phase/time/pathdifference methods. Ocean Eng. 27.2000. 345-363.

115. Mohan, M.; Sarkar, A.; Kumar, R.( ISRO; Me teo ro logy andOceanography Group, SpaceApplications Centre. Ahmedabad380 053, India). An analyticalsource function for a coupled hybridwave model. Proc. Indian Acad. Sci.(Earth Planet. Sci.). 107. 1998. 213-216.

116. Muraleedharan, G.; Nair, N.U.;Kurup, P.G. (Cochin University ofSc ience and Techno logy ;D e p a r t m e n t o f P h y s i c a lOceanography. Fine Arts Avenus,Cochin 682 016, Kerala, India).Application of Weibull model forredefined significant wave heightdistributions. Proc. Indian Acad.Sci. (Earth Planet. Sci.). 108. 1999.149-153.

117. SanilKumar, V.; Deo, M.C.; Anand,N.M.; AshokKumar, K. (NIO. DonaPaula, Goa 403 004, India).Directional spread parameter atintermediate water depth. OceanEng. 27. 2000. 889-905.

118. SanilKumar, V.; AshokKumar, K.;Anand, N.M. (NIO. Dona Paula,Goa 403 004, India). Characteristicsof waves off Goa, west coast ofIndia. J. Coast. Res. 16. 2000. 782-789.

119. SanilKumar, V.; Mandal, S.; Mulik,M.A.; Patgaonkar, R.S. Estimationof wind speeds and wave heightsfrom tropical cyclones during 1961to 1982. Nat l . Ins t . ofOceanography. Dona Paula, Goa(India). 2001. 85 pp.

120. Sarkar, A.; Kumar, R.; Mohan, M.(Space Applications Centre;Oceanic Sciences Division, MOG.Ahmedabad 380 053, India).Estimation of ocean wave periodsby spaceborne altimeters. Indian J.Mar. Sci. 27. 1998. 43-45.

121. Thakur, N.K.; Rao, T.G.; Khanna,R.; Subrahmanyam, C. (NationalGeophysical Research Institute.Hyderabad 500 007, India). Longwavelength magnetic anomaliesover the Bay of Bengal. Curr. Sci.76. 1999. 439-441.

Near shore dynamics

122. Chandramohan, P.; Jena, B.K.;SanilKumar, V. (NIO. Dona Paula,Goa 403 004, India). Littoral driftsources and sinks along the Indiancoast. Curr. Sci. 81. 2001. 292-297.

123. Jena, B.K.; Murty, A.S.N.;Chandramohan, P. (NIO. DonaPaula, Goa 403 004, India). Beachdynamics at Pudhuvalasai in PalkBay. Int. Semin. on Quaternary Sea-Level Variat ion, Shorel ineDisplacement and Coasta lEnvironment. Tamil Nadu (India),[nd] . Proceedings of theInternational Seminar on QuaternarySea-Level Variation, ShorelineDisplacement and Coasta lEnvironment. Rajamanickam, G.V.;Tooley, M.J. eds. New AcademicPubl.. Delhi (India). 2001. 196-203.

124. Kunte, P.D.; Wagle, B.G.;Sugimori, Y. (NIO. Dona Paula,Goa 403 004, India). Littoraltransport studies along west coast ofIndia - A review. Indian J. Mar. Sci.30. 2001. 57-64.

125. Revichandran, C.; Pylee, A. (NIO;Regional Centre. Cochin 682 018,India). Mixing and flushing timescales in the Azhikode Estuary,southwest coast of India. Indian J.Mar. Sci. 27. 1998. 163-166.

126. SanilKumar, V.; Chandramohan, P.;AshokKumar, K.; Gowthaman, R.;Pednekar, P. (NIO. Dona Paula, Goa403 004, India). Longshore currentsand sediment transport alongKannirajapuram Coast, Tamilnadu,India. J. Coast. Res. 16. 2000. 247-254.

127. SanilKumar, V.; AshokKumar, K.;Raju, N.S.N. (NIO. Dona Paula,Goa 403 004, India). Nearshoreprocesses along TikkavanipalemBeach, Visakhapatnam, India. J.Coast. Res. 17. 2001. 271-279.

128. Sinha, P.C.; Rao, Y.R.; Dube, S.K.;Murthy, C.R. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. Hauz Khas,New Delhi 110 016, India). Anumerical model for residualcirculation and pollutant transport ina tidal estuary (Hooghly) of NEcoast of India. Indian J. Mar. Sci.27. 1998. 129-137.

129. Tatavarti, R.; Narayana, A.C.;Kumar, P.M.; Chand, S. (DefenceR&D Organization; Naval Physicaland Oceanographic Laboratory.Thrikkakara, Cochin 682 021,India). Mudbank regime off theKerala Coast during monsoon andnon-monsoon seasons. Proc. IndianAcad. Sci. (Earth Planet. Sci.). 108.1999. 57-68.

Ocean Acoustics

130. Chakraborty, B.; Pathak, D. (NIO.Dona Paula, Goa 403 004, India).Seabottom backscatter studies in thewestern continental shelf of India. J.Sound. Vibrat. 219. 1999. 51-62.

131. Chakraborty, B.; Schenke, H.W.;Kodagali, V.; Hagen, R. (NIO. DonaPaula, Goa 403 004, India).Seabottom characterization usingmultibeam echosounder angularbackscatter: An application of thecomposite roughness theory. IEEETrans. Geosci. Remote Sens. 38.2000. 2419-2434.

132. Joseph, A.; Desa, E.; Desa, E.;Smith, D.; Peshwe, V.B.;Vijaykumar; Desa, J.A.E. (NIO.Dona Paula, Goa 403 004, India).Evaluation of pressure transducersunder turbid natural waters. J.Atmos. Ocean. Technol. 16. 1999.1150-1155.

Ocean Optics

133. Desa, E.; Suresh, T.; Matondkar,S.G.P.; Desa, Ehrlich. (NIO. DonaPaula, Goa 403 004, India). Seatruth validation of sea WiFS oceancolour sensor in the coastal watersof the eastern Arabian Sea. Curr.Sci. 80. 2001. 854-860.

134. Kumar, N.M.; Kumar, P.V.H.; Rao,R.R. (Naval Physical andOceanograph ic Labora to ry .Thrikkakara (PO), Cochin 682 021,Kerala, India). An empirical modelfor estimating hourly solar radiationover the Indian seas during summermonsoon season. Indian J. Mar. Sci.30. 2001. 123-131.

135. Mohanty, U.C.; Kumar, N.M.(Indian Institute of Technology;Centre for Atmospheric Sciences.Hauz Khas, New Delhi 110 016,India). A method for estimation ofnet surface shortwave radiation overthe Bay of Bengal. Indian J. Mar.Sci. 27. 1998. 60-65.

136. Moorthy, K.K.; Saha, A.; Niranjan,K,; Pillai, P.S. (Vikram SarabhaiSpace Centre; Space PhysicsLaboratory. Thiruvananthapuram695 022, India). Optical propertiesof atmospheric aerosols over theArabian Sea and Indian Ocean:North-south contrast across theITCZ. Curr. Sci. 76. 1999. 956-960.

137. Suresh, T.; Desa, E.; Kurian, J.;Mascarenhas, A. (NIO. Dona Paula,Goa 403 004, India). Measurementof inherent optical properties in theArabian Sea. Semin. on 'RecentA d v a n c e s i n B i o l o g i c a lOceanography'. National Institute ofOceanography, Goa, India, 29-31May 1996. Indian J. Mar. Sci. 27.1998. 274-280.

138. Dash, S.K.; Mohanty, P.K. (IndianInstitute of Technology; Centre forAtmospheric Sciences. New Delhi110 016, India). Seasonal cycle ofsurface fields over the Indian Ocean.Indian J. Mar. Sci. 27. 1998. 90-96.

139. Shaji, C.; Rao, A.D.; Dube, S.K.;Bahulayan, N. (Indian Institute ofT e c h n o l o g y ; C e n t r e f o rAtmospheric Sciences. Hauz Khas,New delhi 110 016, India). On thesemi-diagnostic computation ofclimatological circulation in thewestern tropical Indian Ocean.Mausam. 51. 2000. 329-348.

Chemistry and GeochemistryPhysics and Chemistry of water

140. Anilkumar, N.; Sankaranarayanan,V.N.; Josanto, V. (NIO; RegionalCentre. Cochin 682 018, India).Studies on mixing of the waters ofdifferent salinity gradients usingRichardsons number and thesuspended sediment distribution inthe Beypore Estuary, south westcoast of India. Indian J. Mar. Sci.28. 1999. 29-34.

141. Chakraborty, P.B. (RegionalResearch Station (Coastal SalineZone), BCKV. Kakdwip 743 347,India). Water resources ofSundarban delta - Problems andpotentialities. Environ. Ecol. 18.2000. 171-176.

142. De, T.K.; Mitra, A.; Bhattacharyya,D.P. (Calcutta University; Dept. ofMarine Science. Calcutta 700 019,I n d i a ) . P h y s i c o - c h e m i c a lcharacteristics of sewage pollutedKulti Estuary - West Bengal, India.Environ. Ecol. 17. 1999. 808-813.

143. Gopalakrishnan, V.; Kamra, A.K.(Indian Institute of TropicalMeteorology. Dr Homi BhabhaRoad, Pune 411 008, India).Measurements of the atmosphericelectric field and conductivity madeover Indian Ocean during December1996-January 1997. Curr. Sci. 76.1999. 990-993.

144. Mathur, A.K.; Gohil, B.S.; Agarwal,V.K.; Panda, T.C. (SpaceApplications Centre, ISRO; OceanicSciences Division. Ahmedabad 380053, India). Estimation of latent heatflux from ERS-1 ATSR andscatterometer: A new approach.ISRS Natl. Symp. on RemoteSensing Applications for NaturalResources: Retrospective andPerspective. Bangalore (India), 19-21 Jan 1999. Proceedings of ISRSNational Symposium on RemoteSensing Applications for NaturalResources: Retrospective andPerspective, January 19-21, 1999,Bangalore. Adiga, S.; Hegde, V.S.;Ranganath, B.K.; Manavalan, P.;Diwakar, P.G.; Gowda, H.H.;Krishnamurthy, J.; Srivastava, S.K.;Raj, U.; Bandyopadhyay, S.;Thomas, J.V.; Gowrisankar, D. eds.Indian Society of Remote Sensing(ISRS). Bangalore (India). 2000.433-436.

145. Shenoy, D.M.; DileepKumar, M.;Sarma, V.V.S.S. (NIO. Dona Paula,

Goa 403 004, India). Controls ofdimethyl sulphide in the Bay ofBengal during BOBMEX-Pilotcruise 1998. Proc. Indian Acad. Sci.(Earth Planet. Sci.). 109. 2000. 279-283.

146. Shirodkar, P.V.; Somayajulu, Y.K.;Sarma, Y.V.B.; Vijayakumar, R.(NIO. Dona Paula, Goa 403 004,India). Hydrographic characteristicsof the Indian sector of the SouthernOcean. Curr. Sci. 77. 1999. 1273-1282.

147. Subramanian, S.K.; Kannan, L.(Thiagarajar College; Centre forResearch and P.G. Studies. Madurai625 009, India). Environmentalparameters of the Indian marinebiosphere reserve off Tuticorin inthe Gulf of Mannar. Seaweed Res.Util. 20. 1998. 85-90.

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148. Ahmad, S.M.; Dayal, A.M.;Padmakumari, V.M.; Gopalan, K.(National Geophysical ResearchInstitute. Uppal Road, Hyderabad500 007, India). Evolution ofstrontium isotopes in seawaterduring the Middle Miocene: Newresults from ODP Site 758A. J.Geol. Soc. India. 55. 2000. 307-316.

149. Baburajan, A.; Rao, D.D.;Chandramouli, S.; Iyer, R.S.;Hegde, A.G.; Nagarajan, P.S.(Bhabha Atomic Research Centre;Health Physics Division. Bombay400 085, India). Radionuclide ratiosof cesium and strontium in Tarapurmarine environment, west coast ofIndia. Indian J. Mar. Sci. 28. 1999.455-457.

150. Bhushan, R.; Somayajulu, B.L.K.;Chakraborty, S.; Krishnaswami, S.(Physical Research Laboratory;Oceanography and Climate StudiesArea . Ahmedabad, India) .Radiocarbon in the Arabian Seawater column: Temporal variations

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151. Dash, D.R.; Sahu, B.K. (BerhampurUniversity; Department of MarineScience. Berhampur 760 007,Orissa, India). Speciation of copperin surface waters of the RushikulyaEstuary, east coast of India. IndianJ. Mar. Sci. 28. 1999. 370-374.

152. DeSousa, S.N. (NIO. Dona Paula,Goa 403 004, India). Effect ofmining rejects on the nutrientchemistry of Mandovi Estuary, Goa.Indian J. Mar. Sci. 28. 1999. 355-359.

153. DeSousa, S.N.; Sardessai, S.D.;RameshBabu, V.; Murty, V.S.N.;Gupta, G.V.M. (NIO. Dona Paula,Goa 403 004, India). Chemicalcharacteristics of Central IndianBasin waters during the southernsummer. Deep-Sea Res. (II: Top.Stud. Oceanogr.). 48. 2001. 3343-3352.

154. Devi, T.G.; Sobha, V.; Nair, T.V.(University College; Department ofBotany. Thiruvananthapuram,India). Survey of iodide in differentwater bodies of four southernmostd i s t r i c t o f K e r a l a a n dKanniyakumari district of TamilNadu, India. Seaweed Res. Util. 21.1999. 149-153.

155. Eswari, Y.N.K.; Ramanibai, R.(University of Madras; Dept. ofZoology, Unit of Biomonitoring andManagement. Guindy Campus,Chennai 600 025, India). Tracemetal distribution in the estuarinewaters of Chennai, south east coastof India. Int. Semin. on AnalyticalTechniques in Monitoring theEnvironment. Sri VenkateswaraUniversity, Tirupathi, India, 18-20Dec 2000. Analytical Techniques inMonitoring the Environment.Reddy, S.J. ed. Students Offset

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156. Govindasamy, C.; Azariah, J.(University of Madras; Departmentof Zoology. Guindy Campus,Madras 600 025, India). Seasonalvariation of heavy metals in coastalwater of the Coromandel Coast, Bayof Bengal, India. Indian J. Mar. Sci.28. 1999. 249-256.

157. Jayakumar, D.A.; Naqvi, S.W.A.;Narvekar, P.V.; George, M.D. (NIO.Dona Paula, Goa 403 004, India).Methane in coastal and offshorewaters of the Arabian Sea. Mar.Chem. 74. 2001. 1-13.

158. Kaladharan, P.; Pillai, V.K.;Nandakumar, A.; Krishnakumar,P.K. (CMFRI. Cochin 682 014,India). Mercury in seawater alongthe west coast of India. Indian J.Mar. Sci. 28. 1999. 338-340.

159. Krishnaswami, S.; Singh, S.K.;Dalai, T.K. (Physical ResearchLaboratory. Ahmedabad 380 009,Gujarat, India). Silicate weatheringin the Himalaya: Role incontributing to major ions andradiogenic Sr to the Bay of Bengal.Semin. on Present Trends andFuture Directions in Ocean Science.New Delhi (India), 6-7 Oct 1997.Ocean science: Trends and futuredirections. Somayajulu, B.L.K. ed.Indian National Science Academy.New Delhi (India). 1999. 23-51.

160. Kumar, V.; Yaragal, C.; Ramesha,T.J.; Benakappa, S. (University ofAgricultural Sciences; College ofFisheries. Mangalore 575 002,India). Distribution and variabilityof nitrogen and phosphorus inNetravati-Gurpur Estuary, DakshinaKannada. Environ. Ecol. 16. 1998.942-946.

161. Lal, S.; Patra, P.K. (PhysicalResearch Laboratory. Navrangpura,Ahmedabad, India). Variabilities in

the fluxes and annual emissions ofnitrous oxide from the Arabian Sea.Global Biogeochem. Cycles. 12.1998. 321-327.

162. Lal, S.; Lawrence. M.G. (PhysicalResearch Laboratory. Navrangpura,Ahmedabad, India). Elevatedmixing ratios of surface ozone overthe Arabian Sea. Geophys. Res.Lett. 28. 2000. 1487-1490.

163. Manjunatha, B.R.; Shankar, R.(Mangalore University; Departmento f M a r i n e G e o l o g y .Mangalagangotri 574 199, India).Behaviour and distribution patternsof particulate metals in estuarineand coastal surface waters nearMangalore, southwest coast ofIndia. J. Geol. Soc. India. 5. 2000.157-166.

164. Mukhophadhya, S.K.; Biswas, H.;Das, K.L.; Jana, T.K. (University ofCalcutta; Department of MarineScience. 35, B C Road, Calcutta 700019, West Bengal, India). Diurnalvariation of carbon dioxide andmethane exchange aboveSundarbans mangrove forest, in NWcoast of India. Indian J. Mar. Sci.30. 2001. 70-74.

165. Murty, P.V.S.P.; Satyanarayana, D.(Andhra University; School ofChemistry. Visakhapatnam 530 003,AP, India). A comparative study ofa t o m i c a b s o r p t i o nspectrophotometry and anodicstripping voltammetry for thedetermination of trace metals Zn,Cd, Pb and Cu in coastal waters ofVisakhapatnam, east coast of India.Indian J. Mar. Sci. 28. 1999. 365-369.

166. Naqvi, S.W.A.; Yoshinari, T.;Brandes, J.A.; Devol, A.H.;Jayakumar, D.A.; Narvekar, P.V.;Altabet, M.A.; Codispoti, L.A.(NIO. Dona Paula, Goa 403 004,India). Nitrogen isotopic studies inthe suboxic Arabian Sea. Int. Conf.

on Isotopes in the Solar System.Physical Research Laboratory,Ahmedabad (India), Nov 1997.Proc. Indian Acad. Sci. (EarthPlanet. Sci.). 107. 1998. 367-378.

167. Naqvi, S.W.A.; Yoshinari, T.;Jayakumar, D.A.; Altabet, M.A.;Narvekar, P.V.; Devols, A.H.;Brandes, J.A.; Codispoti, L.A.(NIO. Dona Paula, Goa 403 004,I n d i a ) . B u d g e t a r y a n dbiogeochemical implications ofN2O isotope signatures in theArabian Sea. Nature. 394. 1998.462-464.

168. Naqvi, S.W.A. (NIO. Dona Paula,Goa 403 004, India). Nitrogencycling in the suboxic Arabian Sea:Implications for atmosphericchemistry and climate. Semin. onPresent Trends and FutureDirections in Ocean Science. NewDelhi (India), 6-7 Oct 1997. Oceanscience: Trends and futuredirections. Somayajulu, B.L.K. ed.Indian National Science Academy.New Delhi (India). 1999. 87-111.

169. Naqvi, S.W.A.; Jayakumar, D.A.(NIO. Dona Paula, Goa 403 004,India). Ocean biogeochemistry anda t m o s p h e r i c c o m p o s i t i o n :Significance of the Arabian Sea.Curr. Sci. 78. 2000. 289-299.

170. Navekar, P.V.; Naqvi, S.W.A.;DileepKumar, M. (NIO. DonaPaula, Goa 403 004, India). CO2and N2O fluxes from the northernIndian Ocean. Global environmentchemistry. Parashar, D.C.; Sharma,C.; Mitra, A.P. eds. Narosa. NewDelhi (India). 1998. 128-140.

171. Padma, S.; Periakali, P. (Universityof Madras; Department of AppliedGeology. Guindy Campus, Madras600 025, India). Physico-chemicaland geochemical studies in PulicatLake, east coast of India. Indian J.Mar. Sci. 28. 1999. 434-437.

172. Padmavathi, D.; Satyanarayana, D.(Andhra University; ChemicalOceanography Division, School ofChemistry. Visakhapatnam 530 003,AP, India). Distribution of nutrientsand major elements in riverine,estuarine and adjoining coastalwaters of Godavari, Bay of Bengal.Indian J. Mar. Sci. 28. 1999. 345-354.

173. Panigraphy, P.K.; Das, J.; Das, S.N.;Sahoo, R.K. (Regional ResearchLaboratory. Bhubaneswar 751 013,Orissa, India). Evaluation of theinfluence of various physico-chemical parameters on coastalwater quality, around Orissa, byfactor analysis. Indian J. Mar. Sci.28. 1999. 360-364.

174. Patra, P.K.; Lal, S.; Venkataramani,S.; Gauns, M.; Sarma, V.V.S.S.(Physical Research Laboratory.Navrangpura, Ahmedabad, India.NIO). Seasonal variability indistribution and fluxes of methanein the Arabian Sea. J. Geophys. Res.(C: Oceans). 103. 1998. 1167-1176.

175. Patra, P.K.; Lal, S.; Venkataramani,S.; DeSouza, S.N.; Sarma, V.V.S.S.;Sardesai, S. (Phys. Res. Lab..Navarangpura, Ahmedabad, 380009, India. NIO). Seasonal andspatial variabili ty in N2Odistribution in the Arabian Sea.Deep-Sea Res. (I: Oceanogr. Res.Pap.). 46. 1999. 529-543.

176. Ram, A.; Zingde, M.D. (NIO;Regional Centre. Versova, Mumbai(Bombay) 400 061, India).Interstitial water chemistry andnutrients fluxes from tropicalintertidal sediment. Indian J. Mar.Sci. 29. 2000. 310-318.

177. Ramanathan, A.L.; Mani, R.;Manoharan, K.; Kesavan, S.;Kathiresan, R.M. (AnnamalaiUniversity; Department of Geology.Annamalainagar 608 002, India).Study on the groundwater

hydrogeochemistry from Cuddaloreto Puduchatiram, east coast of India.Indian J. Mar. Sci. 27. 1998. 167-172.

178. Sarma, V.V.S.S.; DileepKumar, M.;George, M.D. (NIO. Dona Paula,Goa 403 004, India). The centraland eastern Arabian Sea as aperennial source of atmosphericcarbon dioxide. Tellus (B: Chem.Phys. Meteorol.). 50. 1998. 179-184.

179. Sarma, V.V.S.S.; DileepKumar, M.;Manerikar, M. (NIO. Dona Paula,Goa 403 004, India). Emission ofcarbon dioxide from a tropicalestuarine system. Geophys. Res.Lett. 28. 2001. 1239-1242.

180. Sarma, V.V.S.S.; Narvekar, P.V.(NIO. Dona Paula, Goa 403 004,India). A study on inorganic carboncomponents in the Andaman Seaduring the post monsoon season.Oceanol. Acta. 24. 2001. 125-134.

181. Selvaraj, K. (University of Madras;Department of Geology. A.C.College Campus, Chennai 600 025,India). Total dissolvable copper andmercury concentrations in innershelfwaters, off Kalpakkam, Bay ofBengal. Curr. Sci. 77. 1999. 494-497.

182. Senthilnathan, S.; Balasubramanian,T. (Salim Ali Centre forOrnithology & Natural History;Environmental Impact AssessmentDiv i s ion . Ana ika t t i Pos t ,Coimbatore 641 108, Tamil Nadu,India). Heavy metal distribution inPondicherry harbour, southeastcoast of India. Indian J. Mar. Sci.28. 1999. 380-382.

183. Sharma, M.; Wasserburg, G.J.;Hofmann, A.W.; Chakrapani, G.J.(Max-Plank-Institut fur Chemie.Postfach 3060, D-55020 mainz,Germany). Himalayan uplift andosmium isotopes in oceans and

rivers. Geochim. Cosmochim. Acta.63. 1999. 4005-4012.

184. Vareethiah, K.; Ramadhas, V.;Sivakumar, V. (St. Jude's College;Department of Zoology. Thoothoor629 176, India). Distribution ofnutrients in a bar-built estuary, southwest coast of India. J. Mar. Biol.Assoc. India. 40. 1998. 169-174.

Organic Compounds

185. B a l a c h a n d r a n , K . K . ;Sankaranarayanan, V.N.; Joseph, T.;Nair, M. (NIO; Regional Centre.P.B. No. 1913, Cochin 682 018,India). Non-conservative controls ondistribution of dissolved silicate inCochin Backwaters. 4. IndianFisheries Forum. Kochi, Kerala, 24-28 Nov 1996. The Fourth IndianFisheries Forum, Proceedings. 24-28 November, 1996, Kochi, Kerala.Joseph, M.M.; Menon, N.R.; Nair,N.U. eds. Asian Fisheries Society,Indian Branch. Mangalore (India).1999. 77-79.

186. Bhosle, N.B.; Bhaskar, P.V.;Ramachandran, S. (NIO. DonaPaula, Goa 403 004, India).A b u n d a n c e o f d i s s o l v e dpolysaccharides in the oxygenminimum layer of the northernIndian Ocean. Mar. Chem. 63. 1998.171-182.

187. Bhushan, R.; Dutta, K.; Somayajulu,B.L.K. (Physical ResearchLaboratory; Earth Science Division.Navarangapura, Ahmedabad 380009, India). Concentrations andburial fluxes of organic andinorganic carbon on the easternmargins of the Arabian Sea. Mar.Geol. 178. 2001. 95-113.

188. DeSouza, F.; Bhosle, N.B. (NIO.Dona Paula, Goa 403 004, India).Variation in the composition ofcarbohydrates in the Dona Paula,Bay (west of India) during

May/June 1998. Oceanol. Acta. 24.2001. 221-237.

189. DileepKumar, M.; Sarma, V.V.S.S.;Ramaiah, N.; Gauns, M.; DeSousa,S.N. (NIO. Dona Paula, Goa 403004, India). Biogeochemicals ign i f i cance o f t r anspor texopolymer particles in the IndianOcean. Geophys. Res. Lett. 25.1998. 81-84.

190. Gowda, G.; Gupta, T.R.C.;Hariharan, V.; Katti , R.J.;Lingadhal, C.; Ramesh, A.M.;Nayar, S. Particulate organic carbon(POC) in relation to chlorophyll 'a'and primary production inNethravati - Gurpur Estuary,Dakshina Kannada. 4. IndianFisheries Forum. Kochi, Kerala, 24-28 Nov 1996. The Fourth IndianFisheries Forum, Proceedings. 24-28 November, 1996, Kochi, Kerala.Joseph, M.M.; Menon, N.R.; Nair,N.U. eds. Asian Fisheries Society,Indian Branch. Mangalore (India).1999. 109-111.

191. Rao, B.R.; Veerayya, M. (NIO.Dona Paula, Goa 403 004, India).Influence of marginal highs on theaccumulation of organic carbonalong the continental slope offwestern India. Deep-Sea Res. (II:Top. Study Oceanogr.). 47. 2000.303-327.

192. Sardessai, S.; Wahidullah, S. (NIO.Dona Paula, Goa 403 004, India).Structural characteristics of marinesedimentary humic acids byCP/MAS 13C NMR spectroscopy.Oceanol. Acta. 21. 1998. 543-550.

193. Sardessai, S.; Sarma, V.V.S.S.;DileepKumar, M. (NIO. DonaPaula, Goa 403 004, India).Particulate organic carbon andparticulate humic material in theArabian Sea. Indian J. Mar. Sci. 28.1999. 5-9.

194. Sardessai, S. (NIO. Dona Paula,Goa 403 004, India). Amino acids inthe sedimentary humic and fulvicacids. Indian J. Mar. Sci. 28. 1999.394-399.

195. Sardessai, S.; DeSousa, S.N. (NIO.Dona Paula, Goa 403 004, India).Dissolved organic carbon in theINDEX area of the Central IndianBasin. Deep-Sea Res. (II: Top. Stud.Oceanogr.). 48. 2001. 3353-3361.

196. Yaragal, V.C.; Hariharan, V.;Ramesha, T.J. (Marine ProductsExport Development Authority.Mangalore 575 001, India).Seasonal distribution and behaviorof silicate silicon in the Netravathi-Gurpur Estuary, Dakshina Kannada.Environ. Ecol. 17. 1999. 76-78.

Chemistry of Suspended Matter

197. Bhaskar, P.V.; Cardozo, E.; Giriyan,A.; Garg, A.; Bhosle, N.B. (NIO.Dona Paula, Goa 403 004, India).Sedimentation of particulate matterin the Dona Paula Bay, west coast ofIndia during November to May1995-1997. Estuaries. 23. 2000.722-734.

198. Nair, T.M.B.; Ramaswamy, V.;Shankar, R.; Ittekkot, V. (NIO.Dona Paula, Goa 403 004, India).Seasonal and spatial variations insettling manganese fluxes in thenorthern Arabian Sea. Deep-SeaRes. (I: Oceanogr. Res. Pap.). 46.1999. 1827-1839.

199. Ramanathan, A.; Subramanian, V.(Annamalai University; Departmentof Geology. Chidambaram, TamilNadu 608 001, India). Texturecharacteristics and mineralogy ofthe suspended sediments of theCauvery River Basin, India. J. Geol.Soc. India. 52. 1998. 111-114.

200. Vinithkumar, N.V.; Kumaresan, S.;Manjusha, M.; Balasubramanian, T.(Annamalai University; CAS in

Marine Biology. Parangipettai 608502, Tamil Nadu, India). Organicmatter, nutrients and major ions inthe sediments of coral reefs andseagrass beds of Gulf of Mannarbiosphere reserve, southeast coast ofIndia. Indian J. Mar. Sci. 28. 1999.383-393.

Geochemistry of Sediments

201. Babu, D.S.S.; Nair, A.G.;Damodaran, K.T. (Centre for EarthScience Studies. Akkulum,Trivandrum, Kerala, India). Ageochemical evaluation on theheterogeneity of ilmenite sands fromSouth Kerala. Hand book of placermineral deposits. Rajamanickam,G.V. ed. New Academic Publ..Delhi (India). 2001. 171-179.

202. Badarudeen, A.; Padmalal, D.;Sajan, K. (Centre for Earth ScienceStudies. Thuruvikkal P.O., AkkulamTrivandrum 695 031, India).Organic carbon and totalphosphorus in the sediments ofsome selected mangrove ecosystemsof Kerala, southwest coast of India.J. Geol. Soc. India. 51. 1998. 679-684.

203. Badarudeen, A.; Sakkir, S.; Sajan,K. (Centre for Earth ScienceStudies. Trivandrum 695 031,India). Distribution of Na and K inthe sediments of Veli, Kochi andKannur mangroves, Kerala. IndianJ. Mar. Sci. 27. 1998. 253-255.

204. Balaram, V. (National GeophysicalResearch Institute. Hyderabad,India). Determination of preciousmetal concentrations in apolymetallic nodule referencesample from the Indian Ocean byICP-MS. Mar . Georesour .Geotechnol. 17. 1999. 17-26.

205. Banakar, V.K.; Parthiban, G.;Pattan, J.N.; Jauhari, P. (NIO. DonaPaula, Goa 403 004, India).Chemistry of surface sediment along

a north-south transect across theequator in the Central Indian Basin:An assessment of biogenic anddetrital influences on elementalburial on the seafloor. Chem. Geol.147. 1998. 217-232.

206. Banerjee, R. (NIO. Dona Paula, Goa403 004, India). Mineralogical andgeochemical characters of surfacesediments from the Central IndianBasin. Curr. Sci. 75. 1998. 1364-1371.

207. Banerjee, R.; Roy, S.; Dasgupta, S.;Mukhopadhyay, S.; Miura, H. (NIO.Dona Paula, Goa 403 004, India).Petrogenesis of ferromanganesenodules from east of the ChagosArchipelago, Central Indian Basin,Indian Ocean. Mar. Geol. 157. 1999.145-158.

208. Datta, D.K.; Gupta, L.P.;Subramanian , V. (KhulnaUniversity; Environmental ScienceDisc ip l ine . Khulna 9208 ,Bangladesh). Distribution of C, Nand P in the sediments of theGanges-Brahmaputra-Meghna Riversystem in the Bengal Basin. Org.Geochem. 30. 1999. 75-82.

209. Ferrell, R.E.; Hart, G.F.; Swamy, S.;Murthy, B. (Louisiana StateUniversity; Dept. of Geology andGeophysics . Baton Rouge,Louisiana 70803-4101, USA). X-Ray mineralogical discrimination ofdepositional environments of theKrishna delta, peninsular India. J.Sediment. Res. 68. 1998. 148-154.

210. Gaitan, G.; Vijaykumar, P.(Geological Survey of India; MarineWing. 41, Kirlampudi Layout,Visakhapatnam 530 017, India).Ooids and peloids in the continentalshelf off Kachchh, west coast ofIndia- Inferences to palaeosealeveloscillations. Indian J. Mar. Sci. 27.1998. 190-196.

211. Hanamgond, P.T.; Gawali, P.B.;Chavadi, V.C. (G.S. ScienceCollege; Department of Geology.Belgaum 590 006, Karnataka,India). Heavy mineral distributionand sediment movement at Kwadaand Belekeri Bay beaches, westcoast of India. Indian J. Mar. Sci.28. 1999. 257-262.

212. Karbassi, A.R.; Shankar, R.;Manjunatha , B.R. (TehranU n i v e r s i t y ; I n s t i t u t e o fEnvironmental Studies. P.O. Box14155-6135, Tehran, Iran).Geochemistry of shelf sediments offMulki on the southwestern coast ofIndia and their palaeoenvironmentalsignificance. J. Geol. Soc. India. 58.2001. 37-44.

213. Madhukumar, A.; Anirudhan, T.S.(University of Kerala; Departmentof Chemistry. Trivandrum 695 581,India) . Tannin adsorp t ioncharacteristics of bed sediments ofEdava-Nadayara and Paravurbackwater systems, southwest coastof India. Indian J. Mar. Sci. 29.2000. 37-42.

214. Naidu, P.D.; Malmgren, B.A. (NIO.Dona Paula, Goa 403 004, India).Quaternary carbonate record fromthe equatorial Indian Ocean and itsrelationship with productivitychanges. Mar. Geol. 161. 1999. 49-62.

215. Nath, B.N.; Rao, B.R.; Rao, K.M.;Rao, Ch.M. (NIO. Dona Paula, Goa403 004, India). Rare-earth elementsand uranium in phosphatic nodulesfrom the continental margins ofIndia. Marine authigenesis: Fromglobal to microbial. Glenn, C.R.;Prevot-Lucas, L.; Lucas, J. eds.Society for Sedimentary Geology(SEPM). Tulsa, USA. 2000. 221-232. (SEPM Spec. Publ.. 66)

216. Padmalal, D.; Ramachandran, K.K.(Centre for Earth Science Studies.Thiruvananthapuram 695 031,

India). Significance of heavymineral suite in riverine andestuarine sediments in the southwestcoast of India- A case study. IndianJ. Mar. Sci. 27. 1998. 185-189.

217. Panda, U.C.; Sahu, K.C.;Mahapatra, D.M.; Das, C.R.(Berhampur University; Departmentof Marine Sciences. Berhampur 760007, Orissa, India). Bulk andpartition analysis of heavy metals insediments of the Bahuda Estuary,east coast of India. Indian J. Mar.Sci. 28. 1999. 102-105.

218. Pandarinath, K.; Narayana, A.C.(Physical Research Laboratory;Oceanography and Climate StudiesGroup. Navrangpura, Ahmedabad380 009, India). Elementaldistribution in innershelf sedimentsoff Coondapur, west coast of India.J. Geol. Soc. India. 51. 1998. 493-508.

219. Parthiban, G.; Banakar, V.K. (NIO.Dona Paula, Goa 403 004, India).Chemistry and possible resourcepoten t ia l o f coba l t r i chferromanganese crusts fromAfanasiy-Nikitin seamount in theIndian Ocean. Karnatak University.Dharwad, India. Dept. of Studies inGeology. 1. Convention ofMineralogical Society of India andNatl. Semin.. Dharwad, India, 27-28Nov 1998. First Convention ofMineralogical Society of India andNational Seminar, November 27,28, 1998 - Abstracts. KarnatakUniv.. Dharwad, India. 1998. 41-42.

220. Pattan, J.N.; Shane, P. (NIO. DonaPaula, Goa 403 004, India). Excessaluminum in deep sea sediments ofthe Central Indian Basin. Mar. Geol.161. 1999. 247-255.

221. Pattan, J.N.; Jauhari, P. (NIO. DonaPaula, Goa 403 004, India). Major,trace, and rare earth elements in thesediments of the Central IndianOcean Basin: Their source and

distribution. Mar. Georesour.Geotechnol. 19. 2001. 85-106.

222. Periakali, P.; Eswaramoorthi, S.;Subramanian, S. (University ofMadras; Climate Change ResearchUnit, Dept. of Applied Geology.Guindy Campus, Madras 600 025,India). Deposition, degradation andpreservation of organic carbon inthe Pulicat Lake, Tamil Nadu, eastcoast of India: Preliminary results. J.Geol. Soc. India. 53. 1999. 191-200.

223. Periakali, P.; Eswaramoorthi, S.;Subramanian, S.; Jaisankar, P.(University of Madras; ClimateChange Research Unit, Dept. ofApplied Geology. Guindy Campus,Chennai 600 025, India) .Geochemistry of Pichavarammangrove sediments, southeastcoast of India. J. Geol. Soc. India.55. 2000. 387-394.

224. PrakashBabu, C.; Brumsack, H.-J.;Schnetger, B. (NIO. Dona Paula,Goa 403 004, India). Distribution oforganic carbon in surface sedimentsalong the eastern Arabian Sea: arevisit. Mar. Geol. 162. 1999. 91-103.

225. Raghukumar, C.; Sheelu, G.;LokaBharathi, P.A.; Nair, S.;Mohandass, C. (NIO. Dona Palua,Goa 403 004, India). Microbialbiomass and organic nutrients in thedeep-sea sediments of the CentralIndian Ocean Basin. Mar.Georesour. Geotechnol. 19. 2001. 1-16.

226. Ramasamy, R. (Tamilnadu StateDepartment of Geology and Mining.Chennai, Tamil Nadu, India). Somea s p e c t s o f g e o c h e m i c a lcharacteristics of ilmenite placerdeposits of Tamil Nadu, India. Handbook of placer mineral deposits.Rajamanickam, G.V. ed. NewAcademic Publ.. Delhi (India).2001. 180-193.

227. Rao, D.S.; Banerjee, B.; Maulik,S.C. (National MetallurgicalLaboratory; MPN Division.Jamshedpur 831 007, India).Chemistry of beach placer heavyminerals of Chatrapur, Orissa. Res.J. Chem. Environ. 2. 1998. 11-15.

228. Rathore, S.S.; Vijan, A.R.; Singh,M.P.; Prabhu, B.N.; Misra, K.N.(ONGC; KDM Institute ofP e t r o l e u m E x p l o r a l t i o n ;Geochemistry Division. Dehra Dun248 195, India). Rb-Sr and K-Ari s o t o p i c e v i d e n c e f o rNeoproterozoic (Pan-African)granulite metamorphism from thebasement of Mumbai Offshorebasin, India. J. Geol. Soc. India. 56.2000. 365-372.

229. Roy, D.V.; Chandrasekar, N.;Kumaresan, S.; Udayanapillai, A.V.;Rajamanickam, G.V. (ScottChristian College; Dept. ofChemistry. Nagercoil 629 003,India). Distribution of carbonate andorganic carbon in the sediments ofTambraparani Delta, Tamil Nadu.Environ. Ecol. 17. 1999. 879-885.

230. Roy, S. (Jadavpur University.Calcutta 700 032, West Bengal,India). Marine metallogenesis: Newperspectives. Semin. on PresentTrends and Future Directions inOcean Science. New Delhi (India),6-7 Oct 1997. Ocean science:Trends and future directions.Somayajulu, B.L.K. ed. IndianNational Science Academy. NewDelhi (India). 1999. 129-150.

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233. Singh, B.P.; Prabhakar, V.; Khan,M.S.R.; Pande, A.; Mathur, M.;Misra, K.N. (ONGC; KDM Instituteof Petroleum Explorat ion,Geochemistry Division. Dehra Dun,I n d i a ) . D i s t r i b u t i o n o fpetroporphyrins in crude oils ofvarious Indian sedimentary basins.3. Int. Petroleum Conf. andExhibition. Vigyan Bhavan, NewDelhi, India, 9-12 Jan 1999.PETROTECH-99. Papers of theThird International PetroleumConference and Exhibition, 9-12January 1999, Vigyan Bhavan, NewDelhi. Vol. 4: Hydrocarbonexploration. Bhatnagar, A.K. ed.Indian Oil Corporation. New Delhi,India. 1999. 257-261.

234. Subramanyam, C.; Reddi, S.I.;Thakur, N.K.; Rao, T.G.; Sain, K.(National Geophysical ResearchInstitute. Uppal Road, Hyderabad500 007, India). Gas-hydrates - Asynoptic view. J. Geol. Soc. India.52. 1998. 497-512.

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236. Suresh, N.; Bagati, T.N. (WadiaInstitute of Himalayan Geology;

Sedimentology Group. P.O. Box 74,Dehra Dun 248 001, India). Calciumcarbonate distribution in the LateQuaternary sediments of Bay ofBengal. Curr. Sci. 74. 1998. 977-984.

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238. Udayaganesan, P.; Angusamy, N.;Rajamanickam, G.V. (TamilUniversity; Department of EarthSciences. Thanjavur 613 005,India). Heavy mineral distributionand provenance of Vaippar basinsediments, southeast coast of India.Indian J. Mar. Sci. 27. 1998. 179-184.

239. Valsangkar, A.B.; Ambre, N.V.(NIO. Dona Paula, Goa 403 004,India). Distribution of grain size andclay minerals in sediments from theINDEX area, central Indian Basin.Mar. Georesour. Geotechnol. 18.2000. 189-199.

240. Veerayya, M.; Karisiddaiah, S.M.;Vora, K.H.; Wagle, B.G.; Almeida,F. (NIO. Dona Paula, Goa 403 004,India). Detection of gas-chargedsediments and gas hydrate horizonsalong the western continentalmargin of India. Gas hydrates:Relevance to world margin stabilityand climate change. Henriet, J.-P.;Mienert, J. eds. Geol. Soc.. London,UK. 1998. 239-253. (Geol. Soc.Spec. Publ.. No. 137)

241. Vaz, G.G. (Geological Survey ofIndia; East Coast Operations II,Marine Wing. 41, Kirlampudi

Layout, Visakhapatnam 530 017,India). Verdine and glaucony faciesfrom continental margin off ChennaiBay of Bengal. J. Geol. Soc. India.55. 2000. 297-306.

Atmospheric Chemistry

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244. George, J.P. (National Centre forM e d i u m R a n g e W e a t h e rForecasting. Mausam BhavanComplex, Lodi Road, New Delhi110 003, India). Shortwave radiativeforcing by mineral dust aerosolsover Arabian Sea: A model study.Curr. Sci. 80. 2001. 97-99.

245. Gupta, P.K.; Sharma, R.C.; Koul,S.; Parashar, D.C.; Mandal, T.K.;Mandal, T.K. (National PhysicalLaboratory. Dr. K.S. Krishna Road,New Delhi 110 012, India). Study oftrace gas species includinggreenhouse gases over the IndianO c e a n d u r i n g I N D O E Xprecampaign cruises of 1996, 1997and 1998 on Sagar Kanya. Curr. Sci.76. 1999. 944-946.

246. Jayaraman, A.; Lubin, D.;Ramachandran, S.; Ramanathan, V.;Woodbridge, E.; Collins, W.D.;

Zalpuri, K.S. (Physical ResearchLaboratory. Ahmedabad, India).Direct observations of aerosolradiative forcing over the tropicalIndian Ocean during the January-February 1996 pre-INDOEX cruise.J. Geophys. Res. (D: Atmospheres).103. 1998. 13827-13836.

247. Jayaraman, A.; Satheesh, S.K.;Mitra, A.P.; Ramanathan, V.(Physical Research Laboratory.Navrangpura, Ahmedabad 380 009,India). Latitude gradient in aerosolproperties across the Inter TropicalConvergence Zone: Results from thejoint Indo-US study onboard SagarKanya. Curr. Sci. 80. 2001. 128-137.

248. Jayaraman, A. (Physical ResearchL a b o r a t o r y . N a v r a n g p u r a ,Ahmedabad 380 009, India).Aerosol radiative forcing over theTropical Indian Ocean. Proc. IndianNatl. Sci. Acad. (A Phys. Sci.). 67.2001. 385-394.

249. Kulshrestha, U.C.; Jain, M.;Mandal, T.K.; Gupta, P.K.; Sarkar,A.K.; Parashar, D.C. (IndianInstitute of Chemical Technology.Hyderabad 500 007, India).Measurements of acid rain overIndian Ocean and surfacemeasurements of atmosphericaerosols at New Delhi duringINDOEX pre-campaigns. Curr. Sci.76. 1999. 968-972.

250. Kulshrestha, U.C.; Jain, M.; Sekar,R.; Vairamani, M.; Sarkar, A.K.;Parashar, D.C. (Indian Institute ofChemical Technology. Hyderabad500 007, India). Chemicalcharacter is t ics and sourceapportionment of aerosols overIndian Ocean during INDOEX-1999. Curr. Sci. 80. 2001. 180-185.

251. Kumar, R.; Chaudhury, S.; Peshin,S.K.; Srivastava, S.K.; Mandal,T.K.; Mitra, A.P. (National PhysicalLaboratory. Dr Krishna Road, New

Delhi 110 012, India). First timeobservation of latitudinal andvertical distribution of infra-redradiative flux using radiometersonde over Indian Ocean during theINDOEX IFP-1999 and itscomparison with other Indianstations. Curr. Sci. 80. 2001. 209-215.

252. Lal, S.; Naja, M.; Jayaraman, A.(Physical Research Laboratory.Navarangpura, Ahmedabad, India).Ozone in the marine boundary layerover the tropical Indian Ocean. J.Geophys. Res. (D: Atmospheres).103. 1998. 18907-18917.

253. Mandal, T.K.; Kley, D.; Smit,H.G.J.; Srivastava, S.K.; Peshin,S.K.; Mukherjee, A.D. (NationalPhysical Laboratory. Dr. K.S.Krishna Road, New Delhi 110 012,India). Vertical distribution of ozoneover the Indian Ocean (15 degreesN-20 degrees S) during First FieldPhase INDOEX-1998. Curr. Sci. 76.1999. 938-943.

254. Momin, G.A.; Rao, P.S.P.; Safai,P.D.; Ali, K.; Naik, M.S.; Pillai,A.G. (Indian Institute of TropicalMeteorology. Dr Homi BhabhaRoad, Pashan, Pune 411 008, India).Atmospheric aerosol characteristics t u d i e s a t P u n e a n dThi ruvananthapuram dur ingINDOEX programme-1998. Curr.Sci. 76. 1999. 985-989.

255. Momin, G.A.; Rao, Y.J.; Naik,M.S.; Rao, P.S.P.; Safai, P.D.;Pillai, A.G. (Indian Institute ofTropical Meteorology. Dr. HomiBhabha Road, Pashan , Pune 411008, India). Aitken nucleimeasurements over the sea regionduring INDOEX IFP-99. Curr. Sci.80. 2001. 110-111.

256. Moorthy, K.K.; Pillai, P.S.; Saha,A.; Niranjan, K. (Vikram SarabhaiSpace Centre; Space PhysicsLaboratory. Thiruvananthapuram

695 022, India). Aerosol sizecharacteristics over the Arabian Seaand Indian Ocean: Extensive sub-micron aerosol loading in thenorthern hemisphere. Curr. Sci. 76.1999. 961-967.

257. Moorthy, K.K.; Saha, A.; Niranjan,K. (Vikram Sarabhai Space Centre;Space Physics Laboratory.Thiruvananthapuram 695 022,India). Spatial variation of aerosolspectral optical depth and columnarwater vapour content over theArabian Sea and Indian Oceanduring the IFP of INDOEX. Curr.Sci. 80. 2001. 145-150.

258. Murugavel, P.; Kamra, A.K. (IndianInstitute of Tropical Meteorology.Dr Homi Bhabha Road, Pune 411008, India). Changes in theconcentration and size-distributionof the sub-micron particlesassociated with the sea- and land-breezes at a coastal station. Curr.Sci. 76. 1999. 994-997.

259. Murugavel, P.; Pawar, S.D.; Kamra,A.K. (Indian Institute of TropicalMeteorology. Pashan, Pune 411008, India). Size-distribution ofsubmicron aerosol particles over theIndian Ocean during IFP-99 ofINDOEX. Curr. Sci. 80. 2001. 123-127.

260. N a i r , P . R . ; R a j a n , R . ;Parameswaran, K.; Abraham, A.;Jacob, S. (Vikram Sarabhai SpaceCentre; Space Physics Laboratory,Analytical Spectroscopy Division.Thiruvananthapuram 695 022,India). Chemical composition ofaerosol particles over the ArabianSea and the Indian Ocean regionsduring the INDOEX (FFP-98) cruise- Preliminary results. Curr. Sci. 80.2001. 171-175.

261. Naja, M.; Lal, S.; Venkataramani,S.; Modh, K.S.; Chand, D. (PhysicalResearch Laboratory. Navrangpura,Ahmedabad 380 009, India).

Variabilities in O3, NO, Co andCH4 over the Indian Ocean duringwinter. Curr. Sci. 76. 1999. 931-937.

262. Parameswaran, K.; Nair, P.R.;Rajan, R.; Ramana, M.V. (VikramSarabhai Space Centre; SpaceP h y s i c s L a b o r a t o r y .Thiruvananthapuram 695 022,India). Aerosol loading in coastaland marine environments in theIndian Ocean region during winterseason. Curr. Sci. 76. 1999. 947-955.

263. Parameswaran, K.; Nair, P.R.;Rajan, R. (Vikram Sarabhai SpaceCentre; Space Physics Laboratory.Thiruvananthapuram 695 022,India). Aerosol loading in theatmospheric boundary layer atTrivandrum coast and in theadjoining oceanic environmentsduring the FFP and IFP of theINDOEX. Curr. Sci. 80. 2001. 151-160.

264. Parameswaran, K.; Nair, R.P.;Rajan, R.; Balasubrahamanyam, D.(Vikram Sarabhai Space Centre;Space Physics Laboratory.Thiruvananthapuram 695 022,India). Spatial distribution ofaerosol concentrations over theArabian Sea and the Indian Oceanduring IFP of INDOEX. Curr. Sci.80. 2001. 161-165.

265. Parameswaran, K.; Nair, P.R.;Moorthy, K.K.; Murthy, B.V.K.;Nayar, S.R.P.; Revathy, K.;Satheesan, K.; Rao, P.B.;Bhavanikumar, Y.; Raghunath, K.;Krishnaiah, M. (Vikram SarabhaiSpace Centre; Space PhysicsLaboratory. Thiruvananthapuram695 022, India). Lidar observationsof aerosol layers just below thetropopause level during IFP-INDOEX. Curr. Sci. 80. 2001. 166-170.

266. Parameswaran, K. (Space PhysicsLaboratory; Vikram Sarabhai SpaceCentre. Trivandrum 695 022, India).Influence of micrometeorologicalfeatures on coastal boundary layeraerosol characteristics at the tropicalstation, Trivandrum. Proc. IndianAcad. Sci. (Earth Planet. Sci.). 110.2001. 247-265.

267. Peshin, S.K.; Mandal, T.K.; Smit,H.G.J.; Srivastava, S.K.; Mitra, A.P.(India Meteorological Department.Lodi Road, New Delhi 110 012,India). Observations of verticaldistribution of tropospheric ozoneover Indian Ocean and itscomparison with continental profilesduring INDOEX FFP-1998 and IFP-1999. Curr. Sci. 80. 2001. 197-208.

268. Pillai, P.S.; Jhurry, D.; Moorthy,K.K. (Vikram Sarabhai SpaceCentre; Space Physics Laboratory.Thiruvananthapuram 695 022,India). Aerosol optical depth studiesduring INDOEX: Comparison of thespectral features over coastal Indiawith the pristine southernhemispheric environment overMauritius. Curr. Sci. 80. 2001. 138-144.

269. Rajeev, K.; Ramanathan, V.(Vikram Sarabhai Space Centre;Space Physics Laboratory.Trivandrum, India) . Directobservations of clear-sky aerosolradiative forcing from space duringthe Indian Ocean Experiment. J.Geophys. Res. 106. 2001. 17221-17235.

270. Rao, Y.J.; Devara, P.C.S. (IndianInstitute of Tropical Meteorology;Physical Meteorology and AerologyDivison. Pashan, Pune 411 008,India). Characterization of aerosolsover Indian Ocean and Arabian Seaduring INDOEX IFP-99. Curr. Sci.80. 2001. 120-122.

271. Sarin, M.M.; Rengarajan, R.;Krishnaswami, S. (Physical

Research Laboratory. Ahmedabad380 009, India). Aerosol NO3 - and210Pb distribution over the central-eastern Arabian Sea and their air-seadeposition fluxes. Tellus (B: Chem.Phys. Meteorol.). 51. 1999. 749-758.

272. Sarkar, A.K.; Jain, M.; Parashar,D.C.; Mitra, A.P.; Kulshrestha,U.C.; Cachier, H. (National PhysicalLaboratory. New Delhi 110 012,Ind i a ) . Measu remen t s o fcarbonaceous aerosols at urban andremote marine sites. Curr. Sci. 80.2001. 176-179.

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403 004, India). Aerosol propertiesover the Arabian Sea during thenorth east monsoon. 8. Natl. Symp.,T R O P M E T - 9 9 . R e g i o n a lMeteorological Centre, Chennai(India) , 16-19 Feb 1999.Meteorology beyond 2000.P r o c e e d i n g s o f N a t i o n a lSymposium, TROPMET-99, 16-19February 1999. Bhatnagar, A.K.;Raghavan, S.; Keshavamurthy,R . N . ; G a n e s a n , G . S . ;S h a n m u g a s u n d a r a m , J . ;Rajarathnam, S.; Jayanthi, N.;Subramanian, S.K.; Suresh, R.; Raj,Y.E.A. eds. India MeteorologicalSociety. Chennai (India). 1999. 557-561.

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SEISMOLOGY AND PHYSICS OF THE EARTH'S INTERIOR

R. K. Chadha and D.SrinageshNational Geophysical Research Institute, Hyderabad, India-500 007

Introduction

Seismological research in India, during thelast quadrennium has undergone radicaltransformation due to the availability of highfidelity digital broadband seismological dataand enhanced computing capabilities. TheDepartment of Science and Technology,New Delhi, has launched an ambitiousprogram of funding projects to severalresearch institutes, government departmentsand universities in the country toenhance the detection capabilities of intraand inter-plate earthquakes and to study thesource characteristics of earthquakes andseismic structure of the Indian plate.

With the up-gradation from analog to digitalbroadband seismometry in the countryduring the last one-decade, understandingabout the structure and dynamics of theearth has changed dramatically. Indianscientists are now in a position to understandthe seismic structure and the source in abetter way. The techniques used for oilexploration are now being extended to probethe lithospheric structure in greater detail.The lithospheric architecture deduced fromvelocity images is integrated with complexsurface geology to understand the evolutionof the Indian continental masses. Theimproved characterization of earthquakesources for large and moderate earthquakesin Koyna region in western India, in termsof fault geometry and rupture dynamics hasopened up new vistas for tectonic studies.Although, long-term forecast of earthquakepotential now appears to be a possibility,medium and short-term predictions are still adistant reality. In this scenario, major thrusthas been shifted from earthquake forecastingto earthquake hazard assessment andmitigation. From this point of view strongmotion and ground amplification studies arebeing taken up to provide inputs indesigning safer earthquake resistant critical

structures like dams and nuclear powerplants in the country. Under the GSHAPprogramme, a seismic hazard map has beenprepared for the Indian plate region,comprising the Himalaya, Northeast India,the Indian shield, South China, Nepal,Burma and Andaman regions. This efforthas led to delineation pf eighty-six potentialseismic source zones, the highest risk beingin the Burmese arc, the Northeastern Indiaand the Hindukush regions with PeakGround Acceleration (PGA) values of theorder of 0.35-0.4g.

The significant contributions in seismologyfrom India during the past four years are inareas such as i) understanding reservoirtriggered earthquakes, ii) structure of thepeninsular and extra-peninsular Indiafrom controlled source and passiveseismological experiments like bodywave and surface wave modelling andtomographic inversion studies, iii)studies of the source mechanism andmoment tensor solutions along withnumerical modelling of the stress fields tocomprehend the active tectonics of theIndian plate margins and the shield region,iv) multi-disciplinary geophysical studies inthe source region of damaging earthquakes.

The achievements in seismology researchhave been made possible through intensiveresearch under various time-targetedprojects at different organizations. TheGovernment of India's current emphasis onresearch and development to create wealthand improve the quality of life has led to theformulation of projects relevant to thepresent day needs of the country. Thisreport provides information on thecontributions made by the Indian researchersin the field of seismology during1999-2003.

Bhuj Earthquake

The most important seismological event inthe beginning of the third millennium thatdominated research activities in the countrywas the occurrence of Bhuj (Mw 7.7)earthquake on January 26, 2001. This was agreat intraplate earthquake with a maximumintensity MMI of X+ in Zone V of theseismic zoning map of India. The focalmechanism of the main shock fromwaveform inversion of the regional data andthe aftershocks indicate that the main shockand the most of the aftershocks haveoccurred along a E-W trending and southdipping hidden fault with reverse thrustmotion. The focal depth of this earthquakewas estimated to be around 20 km. Theearthquake claimed several thousand livesand caused widespread damage in the Kutchregion of Gujarat, western India. Highstress accumulation in Kutch is attributed tothe proximity of the triple junction andpivotal point for anti-clockwise rotation ofthe Indian plate.

The aftershocks study of the 2001 Gujarat,India earthquake reveal the seismicallyactive fault dips toward the south at about50° and is interpreted as the fault plane ofthe main shock. The depth distributionof aftershocks is from about 10 to 35 km anddoes not extend to the surface. This isimportant for evaluation of seismic hazard incontinental areas. Large damagingearthquakes can occur on buried faults,which show no displacement or topographicfeatures at the surface. Earthquakes, such asthe 2001 Gujarat event leave very littlesurface evidence of faulting that can be usedto identify past earthquakes.

The most interesting feature of thisear thquake was the widespreaddeformational features on the ground causedmainly by secondary tectonic features due tostrong ground shaking in the meizoseismalarea of 40 km x 20 km. The features mainlyinclude prominent development ofextensional cracking of near surface groundand liquefaction. The earthquake providedan opportunity to study a range ofliquefaction and plastic deformationalfeatures in soft unconsolidated sedimentsand the phenomenon of lateral spreading,especially where there was no surface

expression of coseismic rupture. Evidenceof intense lateral spreading was observed inthe vicinity of the epicentral area where ithas consummated into ubiquitous crackingin the agricultural fields. The patterns ofcracks striking almost E-W are the normalfaults associated with the extensionalregime, with general trend of down throwdue north. The field investigationsindicated that none of the active faults seemsto have moved during the earthquake,suggesting that in all probability themovement took place on a blind thrust andthe rupture did not reach the surface. Soil-gas helium emanometric studies in themeizoseismal area reveal no significanthelium anomaly along surface rupturessuggesting seismic fault must have endedblindly in the subsurface.

Studies of satellite imageries have shownseveral traces of active faults in thepediment zones along the northern marginsof Katrol Hill Range and Northern HillRange correspondingly. The comparison ofpre and post earthquake data from Indianremote sensing satellite IRS 1D LISS-III andIRS P4 clearly brought out emergence of apaleochannel. Resistivity soundings in theepicentral region have shown presence ofshallow water table at the liquefaction siteswhere buildings sunk into the ground. Along the coast emergence of land andactivation of the channels were also clearlyevident.

The 3-D seismic velocity and Poisson's ratiostructures of the source area (60X40 sq km)was carried out to understand the probablecause of triggering the devastatingearthquake at Bhuj using 1948 P and 1865S-waves high quality arrival times from 331Bhuj aftershocks recorded at a temporaryseismic network consisting of 12 seismicstations. Significant velocity variations up to5% and Poisson's ratio up to 10% arerevealed in the aftershock area. The Bhujmainshock is located in a distinctive zone,which is characterized, by high P-wavevelocity (high-Vp), low S-wave velocity(low-Vs) and high Poisson's ratio. Incontrast, areas with high aftershock activityare mainly associated with low Poisson'sratio. The low-Vs and high-Poisson's ratio

anomaly at the Bhuj mainshock hypocenteris visible in the depth range of 22 to 30 kmand extends 10 to 15 km laterally. Theanomaly may be due to a fluid-filled,fractured rock matrix, which might havecontributed to the initiation of a big andkiller earthquake, at Bhuj, western India.

Shear-wave splitting studies were done forsome aftershocks of Bhuj earthquake. Twopatterns in polarization direction in fastshear-wave are found, regardless of thehypocenter location of the individualevents. The NNE-SSW direction in fastazimuth coincides with the direction of themaximum horizontal compressive tectonicstress in the region.

Source Studies

The Indian plate has diverse tectonicenvironments along the plate boundaries,comprising a continent-continent collision inthe Himalaya-Tibetan plateau region, anoblique subduction in the Burmese arc and anascent plate boundary zone in thenortheastern Indian Ocean deformationzone. The Indian shield within the plate is amosaic of cratonic blocks sutured by paleo-rift valley zones, and is known to be aStable Continental Region (SCR). In the lastquadrennium numerous studies have beenundertaken to understand the sourceprocesses for earthquakes, which haveoccurred within the plate interior and alongthe collision zone in the north andsubduction zone in the northeast.

Intraplate Earthquakes

The most active seismic regions of theIndian shield are the Koyna-Warnaregion on the west coast of the Indianpeninsula, which is a classic example ofReservoir Induced Seismicity (RIS), and theNarmada-Son lineament (NSL) zone cuttingEW across Central India, the only activelineament on the Indian shield with at least 5earthquakes of M > 5.5 and continue tointerest the earth scientists in trying tounderstand the seismo tectonics of theseregions.

Koyna-Warna region

Koyna, located near West Coast of India isknown to be the most significant site ofartificial water reservoir triggeredseismicity, starting soon after initiation offilling of the lake in 1961. Reservoirtriggered earthquakes have been occurringuninterruptedly in a small crustal volume of30 x 5 x 10 km3 in the Koyna - Warnaseismic zone. Till date, 18 earthquakes ofM(5.0 (including the 1967 main shock of mb6.3), over 180 earthquakes of M(4 andseveral thousands of M(3 have occurred inthe region. It is observed that earthquakesof M ( 5 ) occurred when certain conditionsare met e.g. water level in Koyna and/orWarna reservoir exceeding the previousmaxima (Kaiser Effect), rate of loadingexceeding 12 m/week and the retention timeof high water level exceeding 90 days. Thecross-correlation analysis between timeseries of the Koyna reservoir levels and thestrain factor (Energy 1/2) calculated forearthquakes of M ( 3.0 suggest that theinitial seismicity in the Koyna region during1963 was triggered after the region attainedsteady state pore pressure by diffusionprocesses, particularly occurred alongvertical strike-slip faults. Subsequently,major episodes of earthquake energy releasetill 1999 show a periodic behavior related tothe annual filling of both the Koyna andWarna reservoirs. Two stages ofearthquake energy release are evident till1996 coinciding with annual filling anddraining of the reservoirs. Since 1996, theenergy release episodes correlate mostly tothe draining cycle of the reservoir levelsindicating a shift in the present dayearthquake activity in the region, which maybe due to a combined effect of both theKoyna and Warna reservoirs. Modeling ofpore pressure front diffusion shows thatwater level change of the order of 1 m in 5days in the surface potential can propagate5-15 % of pore pressure front,corresponding to 0.75-2.25 bars, to thehypocentral depth of 6-8 km. This kind ofstress perturbations are sufficient to triggerseismicity on pre-existing critically stressedfaults in the Koyna-Warna region.

Space-time studies of epicenters in fewselected time windows for moderate sizeearthquakes have shown that the fracturing

processes initiates at shallow depths (< 1km) and then gradually deepens to causethe main shock near the base of theseismogenic layer at about 8-11 km. This nucleation process preceding the mainshock can thus, be considered as animmediate earthquake precursor for Koyna-Warna earthquakes.

With a view to understand the role of porefluids in triggering earthquakes, twenty-onebore-wells of 90 to 250 m depth were drilledin the Koyna-Warna region. These borewells instrumented with pressure transducerscapable of measuring 1 mm change in waterlevels. Most of these wells are sensitive totidal signals and thus acts as strain metersreflecting pressure changes in the medium. These studies have shown five cases ofanomalous changes in well water levels dueto local earthquakes (within 25 km) of 4.3 (M ( 5.2). The epicenters of all theseearthquakes are located within the networkof wells. These wells also found to respondto aseismic events and to transient changesdue to the passage of seismic waves. Theresponse of wells is categorized inthree types, viz., co- and pre-seismic,aseismic and transient changes. The co-seismic steps are understood assudden pore pressure changes related to analteration in in-situ volume strain caused bythe redistribution of stress in the brittle crust.These co-seismic steps are found to bepreceded by persistent water level dropsfrom 2 to 23 days prior to the earthquake. Some anomalous water level fluctuationswere observed which were not associatedwith local or teleseismic earthquakes. Inone case water level fluctuations were alsofound to be associated with passing seismicwaves due to the M 7.9 earthquake atdistance of about 800 km. All theseobserva t ions ind ica te tha t thewells in the network respond tolocal/regional strain changes caused bythe redistribution of stresses in the shallowbrittle crust to different forcing functions.

Narmada-Son and Godavari rift valleyearthquakes. The earthquakes along theNarmada-Son Lineament (NSL) are deeperas compared to most of the Indian shieldearthquakes and there are at least 2 events

along NSL whose depths have beendetermined at lower crustal levels - the 1938Satpura earthquake at 40 km depth (37 - 44km) and the 1997 Jabalpur earthquake at 35km depth. Moment tensor solutions for the21 May 1997, Jabalpur earthquake, using theregional Indian broadband data show reversefault mechanism with the preferred faultplane striking ENE-WSW. This is also seento coincide with the local strike ofthe Narmada South fault cutting across theIndian shield in the same direction.Investigation of the source process revealeda complex rupture process involving a sub-event 2 km above the main event, delayedby about 1 second. The lower crustal depthof the Jabalpur earthquake was also studiedby modelling the sPn phase. The occurrenceof such deep lower crustal earthquakes hasbeen explained by the presence of possiblyserpentenised elliptical intrusives nearMoho, as the probable locales of stressconcentration.

A mechanism to explain Godavari rift valleyearthquakes has been attempted. Usingmoment tensor inversion of broadbandwaveform data a strike-slip fault for 03February 1999 (Mw 3.6) earthquake hasbeen obtained. Based on correlation of theslip vectors of the 1969 Bhadrachalamearthquake and the 1999 Godavariearthquake with faults inferred fromLANDSAT images, the possibility of blockrotation in the faulted paleo-rift valley zoneis inferred.

Interplate Earthquakes

The Chamoli earthquake, which occurred in1999, has generated considerable interestand various studies have been undertaken tounderstand the seismogenesis of thisearthquake. Studies on the Indo-Burmeseconvergence zone in NE India tried toaddress whether the eastward Subduction ofthe Indian plate is active or not?

Chamoli earthquake

The Chamoli earthquake (M 6.6) of 29March, 1999 in the Garhwal Himalayahas been studied extensively and a thrustfault along the detachment surface below the

MCT, at a depth of about 15 km has beeninferred. One of the source models proposedfor this event indicates the earthquakenucleated at the intersection of a transversefault with westward rupture propagationalong the detachment surface whilst anotherstudy shows the earthquake had a southwardpropagation based on the isoseismalmapping.

Mathematical modeling of Himalayanearthquakes

The coeval development of the SouthTibetan Detachment (a regional-scalenormal fault in Tibet) and the Main CentralThrust together with the observeddominance of thrusting in the Himalayas ismodeled using stress simulation analysis. 2Dnon-linear elastic and homogeneous wedgemodels, representing cross-sections of theHimalayas and Tibet are used. Simulatedstresses for a set of boundary conditions inwhich the stress magnitudes are sufficient tocause failure along the wedge base (lowerboundary) and reverse faulting at its toe (updip end of the base), invariably lead to thesimultaneous development of intra-wedgenormal faults. Further, a decrease in shearstrength of the wedge base relative to itsinterior favors the development of normalfaults and/or reduction in the magnitude ofthrusting stresses within the wedge. Theseresults suggest that the presence of arelatively strong Main Himalayan Thrust,the plate boundary fault below theHimalayas, would have favored theoccurrence of thrusting in the wedge.Moreover, a weak Main HimalayanThrust below Tibet along with initiation ofthe Main Central Thrust can explain coevaldevelopment of the South TibetanDetachment. Thus, a relatively strong MainHimalayan Thrust below the Himalayaswould have favored the occurrence ofthrusting whilst a weak Main HimalayanThrust below South Tibet along with theinitiation of the Main Central Thrustwould have been responsible for the coevaldevelopment of the South TibetanDetachment.

A new measure of seismic activity in aregion is defined, which is based on the

concept of integrated fault surface area ofearthquakes in the region. Using thisconcept, we analyze the Harvard CMT dataof the Himalaya-Tibet-Burma seismic belt toestimate the relative proportions of seismicactivity corresponding to reverse, strike-slipand normal faulting in the region. Further,strain rates are computed throughsummation of moment tensor elements ofearthquakes. The study indicates that thedeformation patterns of the Himalaya andthe adjoining Tibetan plateau regions aredistinct. For instance, the seismic activity ofthe reverse fault category changes from 93% in the Himalaya to a mere 2 %in Tibet, which is dominated instead, bystrike-slip faulting (59 %). Strain ratecomputation indicates predominant crustalthickening in the Himalaya with a cleartransition to crustal thinning in the Tibetanplateau region, just across the Indus-Tsangpo suture zone where EW extension isthe predominant mechanism. A model of athinning seismic upper crust in the EWdirection decoupled from a thickeningaseismic lower crust, both in equilibrium, inthe Tibetan plateau, is proposed. In theBurmese arc region, crustal thickening isindicated, but coupled with NS compression.The observed seismic activity ispredominantly of the strike-slip type (56 %),uncharacteristic of subduction zones, whichgenerally display up to 75 % of seismicactivity of the reverse fault category. Thishas implications for Indian plate motionalong the Burmese arc, rather than in thedirection of the subducted slab.

Indo-Burmese convergence zone andAndaman Arc Analysis of all availableseismicity/CMT data from the Indo-Burmese convergence zone and AndamanArc reveal interesting results. The Burma-Andaman arc region is the eastern margin ofthe Indian plate, where an obliquesubduction of the Indian plate under theBurmese plate, is believed to be takingplace.

A detailed study of the Centroid MomentTensor (CMT) solutions in the Burma-Andaman arc region indicates a distinctsegregation of strike-slip and reverse faulttypes of earthquakes in the upper and

lower parts of the eastward subducted slab,and P axis orientations nearly along the arc,rather than across it. It is inferred that theIndian plate, along with its eastwardsubducted Indian slab is shearingpast the Burmese plate in the NNEdirection. Based on the predominantlydown-dip oriented T axis directions anactive subduction in the region has beensuggested. However, a comparative study ofmajor subduction zones in the world bringsout the uniqueness of the Burmese arcregion and provides evidence for cessationof subduction at present. Nevertheless,subduction in this region remains a puzzleand the debate is far from settled.

Crust and Mantle Structure of the IndianPlate. The origin and growth of the Archeancrust has been a subject of intenseinvestigation leading to inferences that afundamental difference existed in theevolution of early and mid-Archean crustthan the late Archean crust. Numerousstudies have been carried out in the last fouryears with broad band experiments initiatedin the South Indian Peninsular shield whichis comprised of Archean Dharwar Craton,South Indian granulite terrain which isArchean in age, Proterozoic Cuddapahbasin, Godavari graben which hasProterozoic ancestry and Cretaceous-Tertiary Deccan Volcanic Province locatedin South India. Using broadband data from32 seismic stations, which were, located onthe Archean and Proterozoic terrains ofsouth India the crustal thickness andPoisson's ratio from receiver functionanalysis has been determined. The crustalthickness in the late Archean Dharwarcraton varies from 34-39 km where anearlier study using broad band data from10 Permanent stations in Indian Peninsularshield have obtained the similar crustalthickness through receiver functionapproach. However, the most significantresult is the presence of anomalous presentday crustal thickness of 42-51 betweenbeneath the mid Archean segment ofWestern Dharwar Craton. Also, the crustalthickness beneath the southern granuliteterrain varies between 42-60 km. ThePoisson's ratio ranges between 0.24-0.28beneath the Precambrian terrains indicating

the presence of intermediate rock type in thelower most crust. The variation in crustalthickness between Archean and Proterozoicterrains has been explained in terms of theircontrasting evolutionary mechanism of thecontinental crust during Archean andProterozoic times.

Local earthquake tomographic studies ofShillong Plateau and Assam Valley in northeast India has revealed strong lateralvelocity variations in P and S wavevelocities with the major seismically activefaults being associated with low velocityZones.

Using the receiver function approach themantle discontinuities in the IndianPeninsular shield have been mapped. Thepresence of a seismic discontinuity in thesubcrustal lithosphere at 90 km depth hasbeen observed. The SV response of the deepupper mantle indicates a prominentsignal corresponding to the 410-kmdiscontinuity, which appears at adelay time of 43.6 s and can clearly betraced over the whole slowness range. Incontrast, the P660s at 67.8 s appears lessclear, probably due to the interference withsignals other than PDs conversions. Thedelay times of P410s and P660s are close tothe global averages, corresponding toconversion depths of 406 and 659 km,respectively. No evidence is found for adiscontinuity around 520 km depth.A correlation of mantle transition zone(MTZ) thickness (temperature) anddistribution of major continents and oceanswas claimed and disputed as well, in fewseismological reports. Most of the studiescarried out in this direction mainly use theSS precursor or Ps conversion data.However, both on local and global scale,significant disagreements based on thesetwo observations do exist in regard to theMTZ thickness distribution over continentsand oceans and the anti-correlated behaviorof the 410 and 660-km discontinuities.Broadband Ps conversion data from oceanichotspot regions and numerous continentalstations (stable and tectonically active areaslike subduction zones) were compared withSS precursor results. The MTZ thicknessvaries in a tight bound between 220

and 280km in both the data sets with theocean and old continents as thelower and higher end members that deviatefrom a global average of 250km. Though theexpected negative correlation between MTZthickness and the apparent 410-km depthbecomes obvious in both the data sets, theslope of this correlation is significantlydifferent for Ps conversion data in contrastto the similar slope from SS data. As theapparent depth of 410-km depends stronglyon the upper mantle velocity structure and inlight of similar image of the MTZ by thesetwo techniques, the observed discrepancymainly arises due to the significantlydifferent view of the average upper mantlevelocity by Ps conversions and SSprecursors as a consequence of theirdifferent ray paths and Fresnel zones.

Seismic Hazard

The scientists have addressed the issue ofseismic hazard in India as early as 1953when a three-zone (Severe, Moderate,Minor hazard) Seismic Zoning map of Indiawas brought out. This map was based on abroad concept of earthquake distribution andgeotectonics. The severe hazard zones areroughly confined to plate boundary regioni.e. the Himalayan Frontal Arc in the north,the Chaman fault region in the northwestand the Indo-Burma border region in thenortheast. The minor hazard zone isconfined to Indian shield region in the southand the moderate hazard zone confined tothe transitional zone in between the two.Since then, many versions of the seismiczoning map of India have been broughtout. A new seismic hazard map for theIndian plate region was prepared under theGlobal Seismic Hazard Assessment Program(GSHAP), as a part of the InternationalLithospheric program (ILP).

For the Indian region, 86 potential seismicsource zones were delineated based on themajor tectonic features and seismicitytrends. The Peak Ground Accelerations(PGA) were computed for 10% probabilityof exceedance in 50 years, at locationsdefined by a grid of 0.5o X 0.5o in theregion 0oN-40oN and 65oE -100oE. Amajority of the Indian plate boundary

regions and the Tibetan plateau region havehazard levels of the order of 0.25g withprominent highs of the order of 0.35-0.4g inthe seismically active zones like theBurmese arc, Northeastern India and North-west Himalaya / Hindukush region. In theIndian Shield region, the regional seismichazard covering a major area is of theorder of 0.1g whereas some locales likeKoyna depict hazard to the levelof 0.20g. The Bhuj region, which is the siteof the recent deadliest intraplate earthquake,indicates PGA values of the order of 0.20-0.25g.

Landslide Hazard Zonation (LHZ) is carriedout to rank different parts of a regionaccording to its potential hazard fromlandslides and requires different causativefactors to be analyzed simultaneously. TheLandslide Hazard Zonation maps are used toidentify and delineate hazard prone areas, sothat environmental regeneration schemescan be initiated adopting suitable mitigationmeasures. If such multi-purpose terrainevaluation maps are used as basis ofpreliminary planning and developmentschemes, it will help in selecting geo-environmentally sound sites that may poseminimum hazard of instability.

Catalog for Himalaya and Northeast IndiaGlobal and regional catalogs for thehistorical, early instrumental and moderninstrumental periods has been compiled andassessed for the completeness of reportingand accuracy in estimation of magnitudes. A relationship between surface wavemagnitude (Ms) and Scalar Moment (M)has been established for northeast region. Moment estimates from the availableCentroid Moment Tensor solutions for theperiod 1977-1996 and the momentsestimated from spectral amplitudes of long-period (90-110s) Love and Rayleigh waveshave been used to derive this relationship formagnitude range 4.5<=Ms<=8.6. Such a logMo vs. Ms relation could be an importantlink for relating the modern instrumentalperiod catalogs and the early instrumentalcatalog. This relationship was used toconvert the early instrumental period (1900-1964) earthquake magnitudes to momentmagnitudes. This conversion is an essential

step towards establishing a uniformmagnitude scale for the entire period of thecatalog (about 1900-present).

Paleoseismology

In Paleoseismology the work primarilyfocused on understanding the earthquakeprocesses in the Indian SCR (StableContinental Region) and along theHimalayan collision zone. The efforts weredirected in understanding the seismotectonicenvironment in the SCR and interplateregions, in understanding the nature ofdeformation, evaluation of past seismicityusing historic and paleoseismologic data andto develop earthquake chronology based ondates of past movements. All these provideuseful inputs for regional seismic hazardevaluation.

Study of the 1819 Rann of Kachchhearthquake revealed a 4.3 m of coseismicuplift occurred during the 1819 earthquakewhilst 1m of uplift was created by the pastearthquakes. This was inferred using digitaltheodilite studies. Trenching excavations ledto identification of one past earthquake,which was dated to have occurred about800-1000 years ago. Studies in Killari,Jabalpur and other locations in thepeninsular India conclude that thereactivation interval on specific faults inthese regions could be of the order of severalthousands of years as the dates for somefaults indicate that they have not movedduring the last 400 thousand years. Based onthe detailed studies on seismites like oldthrust sheets, fault gouge and obsequentfault scarps in addition to the archaeologicalartifacts in Latur lead to the identification ofa paleosiesmic event of 2200(200 year BP,which is supposed to have affected the area.

The paleoseismological studies in theShillong Plateau area, which was affectedmaximum by the Great Assam Earthquakeof 1897 have brought out some interestingresults. By documenting manyliquefaction/deformation features such assand dykes, slump structures, sand blows etcand 14C dating of the organic samplescollected from these features locatedaround the Chedrang Fault and

Krishnai/Dudhnai river sections of theAssam -Meghalaya border region located inthe North West portion of the ShillongPlateau, three paleoseismic events prior to1897 have occurred.

Paleoseismic studies carried out in themeizoseismal area of the great 1934earthquake which affected the Bihar-Nepalregion have resulted in finding ofa p p r o x i m a t e l y h a l f a d o z e nliquefaction/deformation features despiteunfavourable conditions like flash floodsprevailing in North Bihar for preservation ofsuch features. Based on geological evidencefor at least two paleoseismic events to occur(i) between 1700-5300 yrs BP and (ii) 25000yr BP in addition to the well-documentedgreat events of 1833 and 1934 in this regionhave been inferred.

Heat Flow Studies

Thirty new heat flow values determinedin the Southern Granulite Province (SGP)and heat production estimated from radio-elemental measurements at more than 1000sites in the Dharwar greenstone-granite-gneiss province (DP) and the SGP, togetherwith the existing data, bring out contrastingcrustal and sub-crustal thermalcharacteristics between the two Precambrianprovinces in south India. A new approach toheat flow studies has been adopted byundertaking drilling of boreholes in areasbest suited for heat flow determination.The DP has a heat flow range, 25 to 50 mWm-2, with a mean of 36±8 (s.d.) mW m-2.The western part of the province hasmarginally lower heat flow than the easternpart, consistent with the lower levels ofheat production of the major crustal litho-units. The heat production of the gneissesconstituting the basement to the supracrustalrocks west of Closepet Granite range from0.5 to 1.8 µW m-3. In the eastern part, heatproduction of the gneisses ranges from 1.6to 2.9 µW m-3 and that of the granitoidsfrom 1.6 to 4.5 µW m-3. The data confirmthat heat production values can be highlyvariable both laterally and vertically, evenwithin a single craton and does notnecessarily follow any unique model ofheat production distribution with depth, as

has been often assumed in thermal modelingof the continental crust.

A two-layer granulite crust of Late Achaeancharnockites and gneisses characterizes thenorthern block (NB) of the SGP. Overall,the range of heat flow values in the SGP issimilar to that in the adjacent AchaeanDharwar greenstone-granite-gneiss province(DP) in south India. Mantle heat flow in theNB, deduced in the light of heat productionand heat flow data, ranges from 23 to 32mW m-2, which values are distinctlyhigher than 11 to 16 mW m-2 for the DP.The higher mantle heat flow in the NB ofthe SGP appears to be a consequence ofhigher heat production in the subjacentmantle. The temperatures estimates at theMoho range from 285o to 410o C for theDP, and 580o to 660o C for the twoscenarios in the northern block of the SGP.

Climate change in India inferred fromgeothermal observations for the first time inIndia, borehole temperature records havebeen analyzed for deciphering surfaceground temperature (SGT) changes thathave taken place during the past fewcenturies. The data set fills the gap for theunder-represented low latitude regions ~12-28o N in geothermal climate-change studies.

Seventy temperature-depth profilescovering five major climatic provinces ofthe country have been analysed. Theclimatic provinces studied are: (1) North-west, (2) North-central, (3) North-east, (4)Interior peninsula and (5) East coast. Theanalysis revealed an average groundwarming in India of 0.9o±0.1o C over thelast 150 years, an outcome consistent withchanges in surface air temperature (SAT)gleaned from data of 48 meteorologicalstations in the vicinity of the boreholesites. Individual climatic provinces howevershow large variations. A combined analysisof borehole temperatures and meteorologicalSAT records yielded a long-term pre-observational mean (POM) for the SAT,0.8o±0.1o C lower than the 1961-1990mean. When the most recent decade isincluded directly in the analysis, the averagetotal warming in India from the early 1800sto the late 1990s is about 1.2o C. These

observations constitute a clear pointer thatthe warming trends observed in the SATrecords do represent significant increasesfrom the pre-instrumental (19th century)conditions. GPS derived velocity and deformation in theIndian subcontinent GPS measurementswere carried out at 90 sites in the Indiansubcontinent. Leh, Hanle, Almora,Bangalore, Hyderabad and Kodaikanalare permanent stations, which run 24hrs aday and 365 days a year. Delhi, Jamanagar,Bhopal and Shillong are reference stationswhere more than 10days GPS measurementsare available every year. Rest of the sitesare campaign style sites with 3 days ofmeasurement every year. The velocities ofSouth India are not significantly differentfrom the Indian plate velocity of 58±4mm/yrMotion of GPS sites in South India inthe Indian reference frame as well as relativeto IISc station are not significant consideringthe error bars. This implies that South Indiamoves as a rigid plate with velocityapproximately equal to Indian platevelocity. No significant observations can bemade from the motion of GPS sites inGujarat as the two epochs of measurementwere made soon after Bhuj 2001 earthquakeso the velocity vectors are more indicativeof post seismic deformation due to Bhujearthquake. Motion of sites in Ladakhshow that the ITRF velocities of Ladakh are10mm less than the motion of Gharwal sitesand the direction of motion is more towardsthe East. Motion of the sites in the Indianreference frame and relative to IIScgive the convergence between the Indiansubcontinent and Ladakh at 14 to20mm/yr. Convergence rates in Gharwal-Kumaon Himalayas are 10 - 18 mm/yr.ITRF velocities in the Gharwal KumaonHimalayas are slightly higher whencompared to Ladakh and the motion is moretowards North. Motion of Sikkim sites issignificantly different from that of Ladakh,Gharwal Himalayas. Convergence rate in theSikkim region is 10-12mm/y. Velocity ofShillong in N.E India is 54±6 mm/yr. Significant conclusions that arise from GPSstudies are Southern peninsula and Delhimoves as a rigid plate with the velocityapproximately equal to Indian plate velocity.

All the convergence occurs in the 2500 kmstretch of the Himalayan arc from Kashmirto Arunachal and the convergence rates varysignificantly from west to east. This studyalso brings out the Himalayan arc can bedivided in to 10 regions with lengthsroughly corresponding to those of greatHimalayan ruptures (~220km).

Publications

Banerjee, P., and R. Bürgmann (2002). Convergence across the NorthwestHimalaya from GPS measurements, ,Geophys. Res. Lett. ,19, (13).Bhatia, S.C,Ravi Kumar, M., and Gupta, H.K. (1999). Aprobabilistic hazard map of India andadjoining regions. Annali di geofisica, 42, 6,1153-1164.

Chadha, R.K., B.K. Rastogi, P. Mandal andC.S.P. Sarma (1999). Reservoir associatedseismicities in Indian shield, Mem. Geol.Soc. India, 43, 415-423.

Gundu Rao, T.K., Rajendran, C.P., Mathewa n d B . J o h n , B . ( 2 0 0 2 ) .Electron spin resonance dating of faultgouge from Desamangalam, Kerala:Evidence for Quaternary movement inPalghat gap shear zone, southernIndia. Proc. Indian Acad. Sci. (Earth Planet.Sci.) 111( 2), 103-113.

Gupta, H.K., S.N. Bhattacharya, M. RaviKumar and D. Sarkar (1999). "Spectral Characteristics of the 11 May1998 Pokhran and 28 May 1998Chaghai nuclear explosions", CurrentScience, Vol. 76, No. 8, pp. 1117-1121.

Gupta, H.K., R.U.M. Rao, R. Srinivasan,G.V. Rao, G.K. Reddy, K.K. Dwivedi, D.C.Banerjee, R. Mohanty and Y.R.Satyasaradhi (1999). "Anatomy of surfacerupture zones of two stable continentalregion earthquakes, 1967 Koyna and 1993,Latur, India", Geophysical Research Letters,Vol. 26, No. 13, pp. 1985-1988.

Gupta, H.K., I. Radhakrishna, R.K. Chadha,H.J. Kumpel and G. Grecksch (2000). "Porepressure studies initiated in area of

Reservoir-induced Earthquakes in India",EOS Transactions, Vol. 81, No. 14, pp. 145& 151.

Gupta, H.K. (2000). "The Deccan: Site ofWorld's most prominent Stable ContinentalRegion earthquakes", Proc. of INSASeminar on Deccan Heritage, Spl.Publication, Universities Press, pp. 109-134.

Gupta, H.K. (2000). "Major and GreatEarthquakes of the Himalayan Region: anOverview", in Earthquake Hazard andSeismic Risk Reduction, Kluwer AcademicPublishers, pp. 79-85.

Gupta, H.K. (2000). " Earthquake Hazard inDeveloping Countries and GSHAP (GlobalSeismic Hazard Assessment Programme)", Proc. of Second International Workshop on'Earthquakes and Megacities' held duringDecember 1-3, 1999 at Makati City,Philippines, pp.1-8.

Gupta, H.K (2001). Medium term forecastof the 1988 northeast Indian earthquake,Tectonophysics, 338 (3/4), 281-286.

Gupta, H.K (2001). Short-term earthquakeforecasting may be feasible atKoyna, India, Tectonophysics, 338(3/4),353-357.

Gupta, H.K, T. Harinarayana, M. Kousalya,D.C. Mishra, Indra Mohan, N. PurnahcandraRao, P.S. Raju, B.K. Rastogi, P.R. Reddyand D. Sarkar (2001). Bhuj Earthquake of26 January, 2001, Jour.Geol.Soc.India, Vol.57, 275-278.

Gupta,H.K, N. Purnachandra Rao, B.K.Rastogi, D. Sarkar (2001). The DeadliestIntraplate Earthquake, Science,291, 2101-2102.

Gupta,H.K (2002). A review of recentstudies of triggered earthquakes byartificial water reservoirs with specialemphasis on earthquakes in Koyna, India,Earth.Sci.Rev., 58(3/4), 279-310.

Gupta, H.K (2002). Oldest Neolithicsettlements discovered in Gulf of Cambay,Jour.Geol.Soc.Ind., 59, 277-278.

Gupta, H.K, Mandal,P and B.K.Rastogi(2002). How long will triggeredearthquakes at Koyna, India continue?,Curr.Sci., 82(2). Imtiyaz A. Parvez, G.F.Panza, A.A. Gusev and F. Vaccari (2002)"Strong Motion Amplitudes in Himalayasand a Pilot Study for the DeterministicFirst Order Microzonation in a Part ofD e l h i C i t y " , C u r r e n t S c i e n c e ,82(2), 158-166.

Imtiyaz A. Parvez, F. Vaccari and G.F.Panza (2001) "A deterministic seismichazard map of India and adjacent areas". The Abdus Salam International Centre forTheoretical Physics, Pre-Print IC/2001/129.Imtiyaz A. Parvez, G.F. Panza, F. Vaccariand A. A. Gusev (2001) "The strong motionamplitudes from Himalayan earthquakes anda pilot study for the deterministic first ordermicrozoation of Delhi City ". TheAbdus Salam International Centre forTheoretical Physics, Pre-Print IC/2001/130.

Imtiyaz A. Parvez, A.A. Gusev, G.F. Panza& A. G. Petukhin (2001) "Preliminarydetermination of interdependence amongstrong motion amplitude, magnitude anddistance for the Himalayan region". Geophysical Journal International, 144,577-596.

Imtiyaz A. Parvez, A.A. Gusev, G.F. Panza& A. G. Petukhin (1999) "Preliminarydetermination of interdependence amongstrong motion amplitude, magnitude anddistance for the Himalayan region". TheAbdus Salam International Centre forTheoretical Physics Pre-Print IC/99/192.

Imtiyaz A. Parvez and Avadh Ram (1999) "Probabilistic Assessment of earthquake hazards in the Indian Subcontinent". Pure & Appl. Geophy.154(1), 23-40.

Jain, S.K., Murty, C.V.R., Arlekar, J.,Rajendran, C.P., Rajendran, K., and Sinha,R., "The Chamoli India earthquake of March29, 1999",(1999). EERI (EarthquakeEngineering Research Institute, California),Special report Vol. 33, No.7, 1999, 1-8.

Kamal and S. K. Chabak, (2002). ChamoliAftershocks: A view from the nearestSeismic Observatory, Himalayan Geology,23 (1&2), 63-69.

Kumar Dinesh, Khattri K.N., Teotia S.S andRai S. S., (1999), Modelling ofaccelerogrames of two Himalayanearthquakes using a novel semi-empiricalmethod and estimation of accelerogram for ahypothetical great earthquakes in theHimalaya, Current Science, 76, 819-830.

Kayal J.R. (1999). Seismic tomographystudy in Shillong Plateau and Assam Valleyarea, northeast India, Geol. Surv. India Sp.Pub., 49, 143-152

Kayal, J.R., (2000). Seismotectonic study ofthe two recent SCR earthquakes in centralIndia, J. Geol. Soc. India, 55, 123-138.Kayal, J.R., (2000). Seismotectonicstructure in the western Himalaya,Deep Continental Studies in India, 10(1) : 2-5.

Kayal J.R. (2001). Microearthquake activityin some parts of the Himalaya and thep r e s e n t - d a y t e c t o n i cmodel,Tectonophysics, 339, 331-551.

Kayal, J.R, Sagina Ram and O.P. Singh(2002). Mapping the b-value ofthe aftershock source area : The Bhujearthquake of January 26, 2001, Geol. Surv.India Spl. Pub. No. 75, 201-206.

Kayal, J.R.,et al. (2002). Aftershocks of theJanuary 26, 2001 Bhuj earthquake in thewestern India and its seismotectonicimplications. J. Geol. Soc. India, 59, 395-417.

Kayal, J.R. and S. Mukhopadhyay (2002). Seismic tomography structure of the 1993Killari earthquake source area, Bull. Seism.Soc. Am., 92,

Kayal J.R, Pankaj M. Bhattacharya and R.K.Mazumdar, (2002). Fractal dimension andb-value mapping in northeast region, India,Curr. Sci. 82(12), 1486-1491.

Kayal, J.R. (and Dapeng Zhao, O.P. Mishra,Reena De and O.P. Singh), 2002. The 2001Bhuj earthquake : Tomographic evidence forfluids at the hypocentre and its implicationsfor rupture nucleation, Geophys. Res.Lett; 29(24), 51-54.

Kayal, J. R., Nath, S. K., Goswami, T. R.,Roy, S., Ram, S. and Srirama, B. V. (2002).Site Response Study by Shear-wave Spectralanalysis using the 1999 Chamoli Earthquakesequence in Garhwal Himalaya, HimalayanGeology, 23, 45-50.

Krishna, V.G., C.V.R.K. Rao, H.K. Gupta,D. Sarkar and M. Baumbach (1999). "Crustal seismic velocity structure in theepicentral region of the Latur earthquake(September 29, 1993), southern India:inferences from modelling of the aftershockseismograms", Tectonophysics, Vol. 304,pp. 241-255.

Nath, S. K., Sengupta, P. and Kayal, J. R,(2002). Determination of Site Response atGarhwal Himalaya from the aftershocksequence of 1999 Chamoli Earthquake,Bulletin of the Seismological Society ofAmerica, 92, 1072-1081.

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VOLCANOLOGY AND EARTH’S INTERIOR

Abhijit Bhattacharya,IIT Kharagpur, West Bengal

Introduction

New data, evidence and thoughts onmagmatic aspects of the Indian lithosphereculled from literature 1998-2002 arepresented. Reference to a few earlierpublications was inadvertent. Fewreferences could not be reached out, but areadded in the reference list.

Himalayan region

Episodic mafic and acid volcanism duringla te Archaean, Paleoproterozoic ,Neoproterozoic and early Paleozoic arereported from different parts of the HigherHimalayan (HH) and Lesser Himalayan(LH) region (Ahmed et al., 1999; Bhat et al.,1998; Miller et al., 2000; Singh et al., 2002).The oldest intrusives (2.51± 0.8 Ga, Sm-Nbwhole rock) of the Garhwal/Bhowali maficvolcanics in the Kumaun LH and Rampur -Mandi volcanics in Larji-Kullu-Rampurwindow show distinct low-Ti tholeiite trendwith negative anomaly in Nb, Sr, Pb, Ti andhigh positive eNd (+5) (Bhat et al., 1998).The trace element variations especially ineNd is attributed to early depletion and re-enrichment of LREE in the mantle source.These volcanisms are deemed chemicallyequivalent to the basal 2.5 Ga Aravallivolcanics and arguably fed by a singlemantle plume (Bhat et al., 1998).207Pb/206Pb ages (Miller et al. 2000, 2002) ofzircon grains using single grain evaporationtechnique yield considerably lower ages(1800±13 Ma) for the Rampur metabasalts(quartz tholeiite). However, the trace andrare earth element distribution is in unisonwith the observation of Bhat et al (1998) andthought to be derived by moderately highdegree of partial melting in shallow mantle.Ti/V ratio in the range of 20-50 closelyresembles continental flood basalt chemistrywith the incorporation of the crustalcomponent either by crustal contaminationor by recycling of the older crust (Miller et

al., 2000). Paleoproterozoic (1800 –2000 Mausing whole rock Rb-Sr data with initial86Sr/87Sr, 0.7022±0.008) mafic volcanics inthe HH and LH Garhwal and Himachalregion (Ahmed et al., 1999) despite theirtemporal equivalence show distinctlydifferent trace element compositions in thesetwo units. While the LH volcanics showenrichment in LILE and LREE and negativeanomalies in Nb, Pb and Ti, the HHvolcanics are less enriched and lack anynegative anomalies but shows distinctpositive anomaly in Sr. The authorssuggested involvement of an enrichedmantle with subsequent assimilation for thegenesis of the LH volcanics. The HHvolcanics, on the contrary, are considered tooriginate from asthenospheric mantle withminimal crustal assimilation.

In the Ladakh plutonic complex (Ahmed etal., 1998) andesitic-basaltic enclaves,enclosing metamorphosed mafic volcanics(amphibolites) and meta-aluminous toslightly per-aluminous acidic volcanism ofdominantly granodiorite – quartz monzonite– granite affinity are considered to representdifferent stages of arc-maturation related tothe subduction and final closing of the Neo-Tethyan ocean. While the enclaves and themafic volcanics show distinct low-Titholeiite trend, the acid volcanicscharacterize a calc-alkaline trend withenrichment of LILE-LREE and depletion ofHFSE. Per-aluminous Chor granitoid (quartzmonzonite with high Rb: 200-260 ppm, Th:30-50 ppm and U: ~10 ppm) in the lesserHimalaya (Singh et al., 2002) is dated to beNeoproterozoic (825±5 Ma, Pb-Pb ages inzircon). The rocks showing distinctenrichment in LREE and negative Euanomaly are thought to be a product ofanatexis of older Proterozoic crustal rocks.

Granites of younger ages (Dhaoladhargranite whole rock 511.4 ± 9.8 Ma, Vijan etal., 2002), and Kaplas granite (553 ± 2 Ma

(2s) using single zircon U–Pb date, Miller etal., 2001) represent temporally equivalentgranitoids in the Himalaya are correlatedwith Pan African orogeny relatedmagmatism. Trace element distribution inthese granites indicates derivation fromcrustal source. Per-aluminous S-typeleucogranites of Cenozoic age, derivedprimarily from crustal anatexis (Singh et al.,2002) are ubiquitous in the HigherHimalayan zone and are related to theHimalayan orogeny.

Andaman Ophiolite

The geochemical character of plagiogranitesfrom the Andaman Ophiolite Suite isconsistent with its derivation from anoceanic crust (Shastry et. al. 2002). Allelements when plotted on the primordialmantle normalized mult i -e lementspidergrams show enriched patterns. The Fe-Ti enriched mafic rocks associated withoceanic plagiogranites are deemed to haveformed by late stage liquid immiscibility.

The Deccan Province

Deccan flood basalt province (DFBP) spreadover 500,000 Km2 excluding sub-aqueousportion below the Arabian Sea representsfissure-type eruptive that appeared duringthe well-known K-T transition period andfollowed into the Tertiary. The DeccanFlood Basalt Province (DFBP) overlies threemajor rifts initiated at different time inMesozoic as marginal-marine basins, e.g.the Narmada-Tapi-Son Rift, the CambayRift and the West Coast Rift that converge att h e C a m b a y t r i p l e j u n c t i o n(Chandrasekharam, 1985; Sheth andChandrasekharam, 1997). The northerly driftof the Indian subcontinent at the LateCretaceous passed over the Reunion hot spotcausing activation of the plume and rifting(Morgan, 1981). Basu et. al. (1993) suggestthe Reunion hot spot incubated below theIndian subcontinent for at least ~ 3 Ma priorto the main tholeiitic eruption. Alkalinerocks free from any crustal contaminationshow a depleted HREE and enriched LREEpattern (Mundwara Complex; Basu et. al.1993, 1995). A ~14 times higher 3He/ 4Hecompared to atmosphere measured in

pyroxenes comply well with ocean islandbasalts (OIB) and a diagnostic of deepmantle source with relict pristine mantle-reservoir characteristics.

Sheth and Chandrasekharam (1997) raiseseveral important arguments on therelationship of rifting and volcanism,keeping plume activity as the central theme.They suggest ‘pre volcanism extension’evident from several uncontaminatedalkaline complexes reported from thenorthern end of the Cambay Rift andp r e s u m a b l y e m p l a c e d a l o n g‘translithospheric pathways’. Controversypersists over the mode of plume generationand its upward progress. In the plumeimpact model it takes a very short time forthe residence of the plume-head below thelithosphere prior to ascent, and eventuallythe degree of melting is low. Butemplacement of early contamination freealkaline rocks followed by the tholeiiticsuite suggests considerable time lapseduring which incubation of the voluminousplume took place. This probably suggeststhat the plume impact model is not a realisticmodel. Instead, the plume incubation ispossibly the model of choice. It invokesseveral millions of years of plume residencebelow the lithosphere, thinning it slowly andhence generating an initial low degree ofalkaline melt, depleted in HREE at greaterdepth.

Intrabasaltic variants found within the DFBPare late fractionates of the tholeiiticeruptives, and show evidence formetasomatic and related alterations. Sethnaet. al. (1999) report spotted spilitic basaltsfrom Daman. These rocks are characterizedby the typical pillow structure and theirspotted appearance is due to the presence ofbasaltic remnants incorporated by matrix ofspilitic rocks. A sub-aqueous type oferuption accompanied by metasomaticalteration is suggested for their occurrence.Major element analysis of some of thevariants of this kind shows high TiO2

content (1.93-3.92 %) as similar to oceanicbasalts. Chondrite normalized LREEpatterns show elevated peaks for basaltsrelative to spilites, where as MORBnormalized HFSE distribution shows

marked depletion trend in spilites thanbasalts (Sethna et. al., 1999). Some of thelate fractionates have formed ignimbritesafter collapse of the vents as in the north ofMumbai (Sharma et. al. 1998). These areprobably indicative of the waning phases oferuption. Yet, another interestingphenomenon is the occurrence of ferro-enstatite orthopyroxene in basaltic dikesreported from Narmada-Tapi rift zone byChandrasekharam et. al. (2000). Thesebasaltic dikes contain clusters of quenched,prismatic ferro-enstatite crystals hithertounreported from any other flood basaltprovince in the world. The An enrichmenttrend in plagioclase phenocrysts An60-61 (+orthopyroxene) relative to the groundmass(An43-46) suggests their late stagedevelopment from a contaminated melt thatbecame enriched in excess silica, Al2O3 andCaO as a result of early fractionation. Sincea dry magma is unable to produceorthopyroxene due to thermodynamicrestrictions, a semi-aqueous magma(containing not enough H2O that canproduce amphibole) probably took part inthe later reaction to produce orthopyroxene.This, however, strongly suggests a shalycrustal contaminant for the resultingassemblages (Chandrasekharam et. al.,2000).

Aravalli Fold Belt

The late Proterozoic Malani bimodalvolcanics (745±10 Ma; Bhushan, 1999)constitute the largest suite of anorogenicacid volcanics in India succeeding thegranitic activity of Abu pluton. Volcanics ofthe first stage are basalts with minorandesite/trachybasalts. This was followed byhypersolvus and subsolvus granite intrusionthat ceased with ash flow deposits. Theinitial basaltic magma was possiblygenerated at deeper depth by hot spotactivity (Bhushan and Chittora, 1999).Krishnakanta and Vallinayagam (2002)suggest based on LREE and HREEenrichment with large negative Eu anomalyand ancillary geochemical data a crustalorigin for the felsic suite. The volcanismfollowing cratonization of the Aravalli-Delhimobile belt is ascribed to geothermalelevation and spasmodic mafic emplacement

in an extensional regime. Significantly, thepre-Malani basement represented by biotite-trondhjemite and hornblende-granodiorite(Pandit et.al. 1999) is presumably ofArchaean age. A deep-seated origin forhornblende granite is suggested by thepresence of magmatic epidote, and itsincomplete dissolution suggests rapid uplift(cf. Zen and Hammerstrom, 1984). Barker(1979) contends that the biotite trondhjemitesuite is derived from deep-seated low-Ktholeiite.

Continental tholeiites similar to theMesozoic continental flood basalt (CFB)have been reported from Bayana basin in thenortheastern part of this region. (Ahmad andRajamani, 1991; Ahmad and Tarney, 1993;Raza and Khan, 1993; Abu-Ramatteh et.al,.1994). Relationship between incompatibleelement concentrations including REEssuggests subcontinental lithosphericsource(s) for the tholeiites. The sourceregion was enriched following mantlemetasomatization by fluids and/or meltphase enrichment (Raza et.al., 2001).Interestingly, lamprophyres intruding meta-volcanic rocks of Ajabgarh Group of DelhiSupergroup are argued to originate from aless metasomatized mantle, the geochemicalsignatures being more consistent withcrustal contamination during ascent and/oremplacement of melts parental to the suite(Kirmani and Fareeduddin, 2000).

Central India

Geochemical data on volcanic rocks fromdifferent parts of Central India provide anoutline for mantle evolution through time.Metamorphosed pillow basalts of lateArchean-early Proterozoic age from BijawarGroup of rocks document flat REE patternwith weakly positive Eu anomaly (Pati andRaju, 2001). The available data indicate aslightly enriched asthenospheric mantle withmoderate Th/Ta, low La/Ta and relativelyhigh Sr/Ce ratio as source of the metabasaltsgenerated in an extensional tectonic setting(Pati and Raju, 2001). A homogeneous melt,derived from a single source, was possiblyerupted in a shallow sea due todecompression melting in a zone ofextension marginal to the Bundelkhand

Granitoid Complex. The mafic dyke swarmsin the Archean to PalaeoproterozoicBundelkhand massif basement shows muchlower Nb/La ratios compared to theprimitive mantle (Mondal and Ahmad,2001). The geochemical data suggest thebasement to represent a subduction relatedjuvenile crust that experienced lithosphericextension and rifting in response to mantleplume activities.

Western Dharwar Craton

The Sandur schist belt, a part of the westernDharwar craton, and correlatable with theChitradurga schist belt (2.7 Ga; SHRIMP U-PB data after Nutman et al 1996) is a classicgreenstone belt (Manikyamba and Naqvi,1998; Naqvi et al. 2002). The metabasicrocks comprise thloeiitic and high-Mgbasalts and komatiitic ultramafics. Themetavolcanics are characterized by MgObetween 6-30 wt%, Al2O3/TiO2 ~ 10-21 (11-23 for komatiites) and CaO/ Al2O3 ~1 (0.5-2in komatiites). REEs spectra (2-12 timeschondrite) are flat with small +ve/-ve Euanomalies; eNd (+ 0.8649±).00024) resembleCHURT. Ti/V, Ti/Zr, Zr/Y, Sc/Y, Nb/La,Nb/Th, Nb/U, MgO-TiO2, MgO/FeO andAl2O3/TiO2 ratios are also near chondritic.Based on the exhaustive data set, Naqvi et al(2002) suggests a mantle plume derivedfrom an enriched mantle was causal to theorigin of the oceanic volcanic sequence ofSultanpura block. The compositionalheterogeneity especially in HFSE and REEsignatures is attributed to dynamic plumemelting during ascent. According to theauthors, “entrenchment, mixing of AORB,crustal contamination and subduction ofsuch a plume-fed slab may have generatedthe compositional heterogeneities observedin the Sultanpura block”.

Eastern Dharwar Craton

There have been several attempts tocharac ter ize Archaean-Proterozoicvolcanism in the Dharwar craton. Significantamong these is the high Mg granitoid (Qtz-monzodiorite) xenoliths reported fromwithin the Archaean granodiorite and graniteof eastern Dharwar craton. The rocks arecharacterized by high mg# (44-57), show Ba

and Cr enrichment, and moderately slopingchondrite-normalized REE patterns (LREEenrichment and HREE depletion).Sarvothaman (2001) interprets the rocks tohave been derived from a LREE depletedand high Mg- source such as a mantleperidotite. The author argues that thisfinding and its interpretation establish theinvolvement of mantle magmatism in theformation of pre-Archaean crust of theDharwar craton.

Giriritharan and Rajamani (1998) presentdata on amphibolite facies mafic volcanicsfrom the Hutti-Maski schist belt. The rocksare Fe-rich tholeiites with flat to LREEenriched rare earth patterns. Trace elementmodeling indicates that the tholeiiticprotoliths were formed from mantle sourcesvariably enriched by partial melts atpressures > 25 kbar.

The intracratonic Cuddapah Province in theEast Dharwar craton is a host to profusemid-Proterozoic kimberlite pipes andlamprophyre dykes along its eastern andwestern margins. The lamprophyres arepotassic in nature, nepheline and/or leucitenormative, characterized by highlyfractionated chondrite normalized REEpatterns, with initial 87sr/86Sr varyingbetween 0.703-0.705. (Madhavan etal.1998). The authors contend that thegeochemical signature of the ultra-potassicmagmas is consistent with derivation from amantle source or a source near the crust-mantle boundary. But on a cautionary notethe authors state “As a deviation, Ravipadulamprophyre fails to record substantialdegree of mantle enrichment whereas theKellampalle lamprophyre magma lying tothe west of Ravipadu, appears to havedifferentiated from a mantle derived magmaby olivine fractionation”. Madhavan et al(1999) reports the occurrence andgeochemistry of mid-Proterozoic alkalineand non-alkaline inrtusives in and aroundthe Cuddapah basin. Based on major andtrace element (enriched in Sr, Ba, Nb, Zr)variations and highly fractionated enrichedrare earth element spectra (Lacn ~ 100; Lucn

~ 10), the authors suggest the intrusivesunderscore the importance of mid-

Proterozoic intraplate alkaline magmatism inEastern Dharwar.

The Uppalapadu alkaline plutonic complex(1348 ± 41 Ma) to the east of the CuddapahBasin along the western margin of theEastern Ghats Mobile Belt comprisestholeiitic gabbro and ferrosyeniterepresenting a subalkaline series. Thetholeiitic and calc alkaline suites formedprior to emplacement of the alkalinecomplexes (Ratnakar and Sharma 1994,Vijayakumar and Ratnakar 1995a). AtUppalapadu, it is inferred that a higherdegree of partial melting of mantle hasproduced the subalkaline (tholeiitic) basalticliquids, whereas a lower degree of meltingof enriched garnet-lherzolite mantle andsegregation at relatively deeper levelsformed the alkaline basaltic liquids (KrishnaReddy et al. 1998).

The Ravipadu Gabbro Pluton is an intrusivewithin Precambrian crust (composed ofamphibolite and granulite) in the Prakasamigneous province. It is sandwiched betweenthe Eastern Ghats Mobile Belt and theCuddapah basin. The texture of theRavipadu gabbro indicates its formation bycrystal-liquid fractionation of subalkalinetholeiitic magma under anhydrousconditions. Petrogenetic model designed insupport of its formation suggests that theparental liquid is derived by low degrees ofmelting of late Archaean underplatedkomatiite/basaltic komatiite crust; crustalmelting being induced by a mantle plume(Vijayakumar and Ratnakar, 2001). 23 kmNorth of Anantapur is an east-west trendingbody, the Ramdaspeta Gabbro-Anorthosite,intrusive into tonalite-granodiorite-adamellite suite of Peninsular gneiss of eastDharwar craton. It is a composite layeredbody comprising melanocratic cumulusgabbro, porphyritic gabbro and anorthositicgabbro. Differentiation of tholeiitic magma,as suggested by Ashwal (1993), may beresponsible for the evolution andemplacement of Ramdaspeta intrusive into athickened crust (Suresh et al. 1998).

The mid Proterozoic metabasic rocks fromthe Khammam schist belt separating theDharwar craton from the Eastern Ghats

Mobile Belt are tholeiites, cluster in theferrobasalt field of Jensen (1976), and aredepleted in incompatible elements,especially HFSEs relative to MORB.Chondrite-normalized REE patterns are discshaped (characteristic of boninite) or areweakly fractionated LaN/YbN ~ 1.66.Overall, the Khammam metabasites indicatebonninitic rather than a komatiitic affinity,and formed by process similar to thoseproducing present day bonninites fromdepleted upper mantle source in a supra-subduction region (Bose and Moulick,1999). In sharp contrast to the inference ofBose and Moulick’s (1999), Hari Prasad etal (2000) based on immobile element (Zr –Y – Ti) signatures advocate an ocean islandarc or continental margin island arc settingsfor the Khammam metabasites.

Chatterjee and Bhattacharji (1998, 2001)present new data and provide a detailedaccount of the petrology, geochemistry andgeochronology of mafic dykes and sillswithin and along the margins of theCuddapah Basin. According to the authors,the igneous activity around the basin wasintermittent beginning at 2400Ma, peaked ataround 1200-1400 Ma and continued till 800Ma after sedimentation ceased. TheCuddapah basin dykes and sills are mostlytholeiites characterized by enrichment ofincompatible elements relative to MORB.The authors argue that the tholeiites wereformed via fractional crystallization (5 kbar,1000-1100°C) of locally heterogeneousmantle derived melts reflected by variationsin Ba/Rb, Ti/Zr, Ti/Y Zr/Nb and Y/Nbratios.

South Indian Craton

In the high-grade granulite region in SouthIndia, Proterozoic mafic dyke swarms showLILE and LREE enrichment, and Nb, Tadepletion (Radhakrishna and Mathew,1998). Dolerite dykes in the Tiruvannamalaiand Dharmapuri area is explained by crustalcontamination and derivation from anenriched lithospheric mantle, developedmuch earlier than dyke intrusions during amajor crust building event in Archaean(Radhakrishna and Mathew, 1998).Dehydration melting induced by

decompression and lithospheric attenuationor impingement of partial melts from plumeheads at the base of the lithosphere is citedto be the cause for dyke emplacement.

Geochemical data from Proterozoic alkalinecarbonatite complex of Samalpatti in TamilNadu suggest their origin by liquidimmiscibility from carbonated nepheliniticmagma generated from an enriched mantlesource (Shrivastava, 1998)

Singhbhum Craton

Minor rhyolite intrusives spatially associatedwith granophyric granites occur along theeastern and southwestern fringe of theArchaean Singhhum Granite batholith in theeastern Indian Craton. These have intrudedArchaean mafic-ultramafic rocks that formthe basement over which unconformablyoverlies the granites of Proterozoic age. It isinferred that the rhyolites were generated bypartial melting of Archaean continental crust(Sengupta et al. 1998).

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