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Adv. Space Res. Vol. 13, No. 5, pp. (5)273(5)276, 1993 02731177)93 S 2 4 . I X IPrinted in Great Britain. Allrights reserved. C o p y r i g h t 1993 COSPAR
SATELLITE DATA APPLICATION IN THESTUDY OF VARIABILITY OF DATES OF
ONSET OF INDIAN SUMMER MONSOON ANDITS INFLUENCE ON YIELD OF CROPS
V. R. Mujumdar, V. R. Deshpande and D. K. Paul
IndianInstitute ofTropical Meteorology, Pashan, Pune-411008, India
ABSTRACT
Agriculture in India is strongly dependent on rainfall. Besides th e quantum of rainfall,
th e timely commencement of rainy season (onset of monsoon) ha s also dominating influence
on th e yield of crops. Timely sowing especially in case of crops g ro wn u nd er rainfed
condition gives b etter yields. It is therefore necessary that th e beginning of cropping
season is linked with t he f i rs t monsoon rainfall which would provide th e required moisture
f or th e sowing operations. Th e most variable nature of ons e t an d subsequent behaviour of
summer monsoon season makes th e task difficult f o r t he farmers an d planners to plan their
cropping strategies an d to estimate t he f i na l yield. Th e year to year variability of dates
of ons e t of monsoon over different parts of India have been s tu di ed b as ed on satellite
derived data. Th e yield of different crops under early, normal an d late ons e t ar e also
studied. Delayed onset, is f o u n d to have adverse effect on th e yields.
INTRODUCTION
An agriculture sector in India, today provides livelihood to about 70 percent of labourforce , contributes nearly 35 percent of ne t national product an d accounts f o r sizeable share
of t ot al value of countrys export /1/. B ut s i nc e mor e t han 70 percent of th e cultivated
land in th e country is nonirrigated, th e Indian farmers continue to depend on th e monsoonrainfall which gives nearly 70 percent of th e annual rainfall during th e f o u r months (June
September) of th e season assuring enough supply of moisture f o r t he kharif crops (rainfed
summer crops ). Irregularities in th e commencements of rainfall (onset of monsoon), its
c e s sa t io n , d u ra t io n , distribution an d intensity over any region results in th e variation
in th e crop yields. In many parts of India, after a long dr y period of ho t summer (April
May) a fe w spells of premonsoon thundershowers supply firs t moisture to th e soil.Thereaft e r with t he o n se t of th e monsoon th e region receives 4 to 5 days of sustained rainfall
supplying enough moisture f o r t he sowing operations of most of th e kharif crops / 2/ .
Depending upon th e kind of crop, soil type, terrain features an d occurrence of f i r s t s p el lof rainfall which could built up enough moisture in th e soil, Raman /3 / ha s determined th e
normal dates f o r commencement of sowing rains in th e district scales f o r Maharashtra state.
Th e fie ld experiments conducted by Singh et. al. at Ranchi / 4 / a nd by J os eph at K er al a /5 /ha s respectively observed that timely sowing of rice during t he o n se t of monsoon ha s
recorded a good growth of crop with high g ra in y ie ld a nd delayed transplanting of rice due
to late arrival of monsoon rains resulted into low yield of th e grain. Prior knowledge of
th e d at e o f commencement of monsoon rains would thus guide th e farmers in planning th esowing operations.
Fo r good yield o f c ro ps , critical conditions of weather s uc h a s rainfall, cloudiness or
sunshine ar e essential at various s tage s o f c ro p growt h . Heavy showers just aft e r sowing
or germination may compact th e soil aft e r drying or wash away t h e s e ed s, kill seedlings
by water logging or lessen th e fertility producing poor yield. Groundnut, a major kharif
c ro p i n Gujarat with life cycle of 1 1 0 to 1 40 days grows on warm an d moderately moist
climate, requiring abundant sunshine an d moderate r a in f a l l. T he critical period of moisture
requirement f o r t he crop is at th e initial stages of sowing an d germination bu t at th e time
of maturity or flowering prolonged ra in o r cloudy weather may r es ul t i n poo r yield /6/.
This paper attempts to study th e yield of Groundnut a nd i t s relation with th e time of ons e t
of monsoon a nd i ts further development during th e season over Gujarat based on satellite
derived dat a s uc h as Outgoing Longwave Radiation (OLR) or cloud imageries during monsoon
season with t h e yie ld of groundnut in the state of Gujarat.
DATA AND METHODOLOGY
Th e ons e t date f o r well distributed stations over th e country have bee n analysed f o r t heperiod of 33 years (19601992). T h e y i el d of groundnut during th e monsoon seasons of 1 96 5
through 1 987 ha s been calculated from th e data published by Government of India /7, 8/. The
J A S R 1 3 : 5 S
(5)273
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(5)274 V. R . Mujumdar et al.
e 70 75E25 N ~ ~~t JUN 25N
DSA
SAH M
VVL
20 D M N 20
BMB
I I I I I
70 75E
Fig. 1 . Normal ons e t dates of summer monsoon over Gujarat
daily OLR d at a a t 2.5~ latitude/longitude intersections from NOAA Polar orbiting satellite
obtained f o r period 1 97 4 1986 from th e Climate A nalysis C entre, US A were averaged f o r
th e latitudes 2O~to 25~Nan d longitudes 7O~to 75~E to analyse th e various spells of
rainfall, cloudiness or bright s un s hi ne o ve r Gujarat. In 1 987 in absence of OLR data th e
percentage of c lo u d c o ve r over Gujarat region was estimated by visually inspecting th e
cloud imageries received from INSAT1B. It wa s then plotted an d analysed to determine
epochs of dr y and we t periods during monsoon over Gujarat.
DISCUSSION AND RESULTS
Onset a nd T h e Yield of Groundnut
Normally th e onset of monsoon over Kerala, the Southern ti p of India occurs on 1 June,
which further advances northward across th e southern peninsula an d covers th e entirecountry by 15 July / 2/ . Th e rainy season commences at th e Southern en d of Gujarat near
Dahanu (2ON, 7 2 E) j u st aft e r 10 June an d passing over Ahmedabad (23.2N, 72.5~E) o n J un e14 it reaches D e es a ( 2 4. 2 N, 72.5~E) near northern boundary of Gujarat b ringing nearly
80 % of t he s ta te under th e influence of monsoon on June 21 an d covers th e entire state
by 1 July (Figure 1 ) . Th e analysis of th e standard deviation of date o f onsets over Indian
stations show maximum y ea r t o y e ar variation over Gujarat region of 9 to 10 days
compared to 7 to 8 d ay s o ve r re st of th e country. Th e withdrawal of th e monsoon seasons tart s fro m northwestern parts of India from September 1 onwards, an d hence a delay in
th e onset of monsoon over Gujarat (b y mor e t han 2 weeks) does affect t he t o ta l duration
a n d t he amount of seasonal rainfall significantly leading t o poo r yield of crops / 9/ .
F or t he years 1 96 5 to 1 987 th e m ap s o f northern limits of monsoon which gives t he d ay today position of advance of monsoon over various parts of th e country during t he o ns et
phases w er e us ed to determine the o ns et d at es f or the Gujarat state during th e various
y ears . W e define ons e t date f o r t he s ta te when more than 7 0 % of t he s ta te h as been covered
by th e monsoon rain. T hu s 2 0 June is th e dat e by which monsoon normally covers aro un d 7 0
percent of th e entire state. Th e correlation between th e yield of groundnut in Gujarata nd t he o n se t date o ve r th e s ta te f o r th e year ha s shown th e inverse relationship
(correlation coefficient 0.55, significant at 1% level) signifying that th e delay in
ons e t of monsoon adversely affects th e yield of groundnut in t h e s t at e (Figure 2).
Intraseasonal Variations in OLR an d Yield of Groundnut
Th e time series analysis of average O LR values over Gujarat ha s been used to study th eda y to day variations in weather conditions over Gujarat. Followir~Kripalani et . al. / 1 0 /
a da y is considered to be a rainy da y when OLR value is 22 0 W/ m or less. Table 1 givest he o n se t dates, percentage departures of seasonal rainfall from n o rm al , t he number of
rain spells during th e season a nd t he yield of groundnut f o r Gujarat in Kg/hectare produced
during th e typical years of 1 97 5 , 1 97 9, 1 98 0, 1 982 an d 1 987 .
In 1975 a bumper yield o f groundnut reaching upto 1240 kg/hectare was obtained in Gujarat.
Figure 3a s h ows that along with normal onset of monsoon around 20 June with a good spellof rainfall as s ee n fro m lo w O LR values ha s probably built up enough moisture in soil
during the germinating stage o f the crop. Subsequently four well distributed alternate
spells of rainfall an d sunshine appears to properly match th e requirements of variousstages o f c ro p growth probably resulting into a bumper yield. Though 1 97 9 wa s a drought
year f o r I nd ia as a whole, three good spells of rainfall aft e r little delayed onset, with
Intermittant breaks ha s g iv en f ai rl y b et te r y ie ld (Figure 3b). Th e fluctuations in OLR
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(5)276 V.R.Mujumdar et aL
: is jL ;V : I \v r~W ISO ____________________________________________ 60
~32U ~ 320~ C c ) 980 C d ) 982
~~T-::T1i~-0 20 30 0 2 0 3 0 9 IS 29 5 5 25 0 20 30 0 20 30 9 IS 21 5 II 25JuNE JULY LU G I .~UN6 LUG
Fig.3. Mean OLR values over Gujarat (2O~25Nand 7O~75~E)during June to
September f o r t he years a) 1 97 5 b) 1 97 9 c) 1 980 an d d) 1 982
various spells of weather patterns i n t he s ea so n, b e t une d with the typical weatherconditions required at various growth stages of th e crop. Satellite data (OLR) is f o u n d
to be very much useful in monitoring year to year variability in the daily patternso f weather sequences.
The study shows that the various epochs o f sunshine, cloudiness or rainfall during monsoon
over different parts o f India ca n be monitored by analysing satellite derived data a nd t he
information when matched with th e requirements at various growth s tage s o f a certain crop
it is possible to estimate th e final yield which may be of vital importance to th e farmers
an d planners. A further study of long term satellite data over various parts o f the country
may also provide a guideline as to which crop will give a b et te r y ie ld in a particular
region.
REFERENCES
1. INDIA, A Reference Annual, Ministry of I & B, Govt. of I n di a ( 1 9 8 8 8 9 )
2. India Meteorological Department, Climatological Atlas for Airmen in India (1943)
3 . C.R.V. Raman, Scientific Report No. 216, India Meteorological Dept. (1974)
4. R.S. Singh, D.C. Ghosh and V.C. Srivastava; Indian Journal of Agronomi,36(2) 159164, ( J un e 1 9 9 1)
5 . Kamalan Joseph, Indian Journal of Agronomi, 36(1) 8386 (March 1991)
6 . J.R. Kakade, Agricultural Climatology, New Delhi Metropolitan (1985)
7 . Area Production of Principal Crops in India Directorate Economics and Statistics;
Department of Agriculture and Cooperation; Ministry of Agriculture, Govt. o f India
(198485)
8. India Data Base, The Economy Annual Time Series Data Vol. II
9. V.R. Mujumdar, V.R. Deshpande, P.V. Puranik, V.V. Bhide and D.K. Paul
Book by M/s Tata Mc Graw Hill on TROPMET92 in press
10. R.H. Kripalani, S.V. Singh and P.A. Arkin, Beitr. Phys. Atmosphere 159168 (August
1991).