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Monsoon of South Asia
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From Wikipedia, the free encyclopedia
The monsoon of South Asia is among severalgeographically distributed observations of globalmonsoon taking place in the Indian Subcontinent. Inthe Subcontinent, it is one of oldest weatherobservations, an economically important weatherpattern over June through September every year,and the most anticipated weather event and uniqueweather phenomenon. Yet it is only partiallyunderstood and notoriously difficult to predict.Several theories have been proposed explaining theorigin, the process, the strength, the variability, thedistribution and the general vagaries of the monsoonof the Indian Subcontinent, but understanding of thephenomenon and its predictability are still evolving.
The unique geographical features of thesubcontinent, along with associated atmospheric,oceanic and geophysical components, are influential
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Annual average monsoon precipitation over India over 110 years.The long term average precipitation has been 899 mm frommonsoon.[1] However, monsoon varies over the Indian Subcontinent,within a ±20% range. Rains that exceed 10% typically lead to majorfloods, while a 10% shortfall is a significant drought.[2]
in ensuring the anticipated behavior for a monsoon inthe Indian Subcontinent. Due to its effect onagriculture, flora and fauna and the general weatherof India, Bangladesh, Bhutan, Pakistan, Sri Lanka,etc., among other economic, social andenvironmental effects, amonsoon is one of the mostanticipated, followed[3] andstudied weather phenomena ofthe Indian subcontinent. It hassignificant impact on the overallwell-being of subcontinentresidents and has even beendubbed the "real financeminister of India".[4][5]
Contents [hide]
1 Definition
2 Background
3 Mechanism of Monsoon3.1 Effect of Geographicalrelief features
4 Features of Monsoon Rains4.1 "Bursting" of MonsoonRains
4.2 Monsoon RainVariability ("Vagaries")
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5 Ideal and Normal MonsoonRains
6 Theories for Mechanism ofMonsoon
6.1 Traditional Theory6.1.1 Process ofMonsoon creation
6.2 Dynamic Theory6.2.1 Process ofMonsoon creation
6.3 Jet Stream Theory6.3.1 Process ofMonsoon creation
7 Theory for "Bursting" ofMonsoon
7.1 Dynamic Theory
7.2 Jet Stream Theory
8 Theories for MonsoonVariability
8.1 The Jet Stream effect
8.2 El Niño-SouthernOscillation (ENSO) effect
8.3 Indian Ocean Dipoleeffect
8.3.1 Equatorial IndianOcean Oscillation
9 Monsoon Rain predictionmodels
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9.1 Seasonal Prediction ofIndian Monsoon (SPIM)
9.2 Indian MeteorologicalDepartment Model
10 Significance10.1 Geographical (WettestSpots on Earth)
10.2 Agricultural
10.3 Economic
10.4 Social
10.5 Travel
10.6 Environmental
11 Notes
12 See also
13 References
14 External links
Definition [ edit ]
Monsoon, derived from the Arabic word "mausim" meaning "season", although generally definedas a system of winds characterized by a seasonal reversal of its direction,[6] lacks a consistentdetailed definition. Some examples are given below:
The American Meteorological Society defines it as a name for seasonal winds, first applied tothe winds blowing over the Arabian Sea from northeast for six months and southwest for sixmonths.[6] Later it has been extended to similar winds in other parts of the world.
Intergovernmental Panel on Climate Change (IPCC) describes Monsoon as a tropical and
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subtropical seasonal reversal in both the surface winds and associated precipitation, causedby differential heating between a continental-scale land mass and the adjacent ocean.[7]
Indian Meteorological Department defines it as the seasonal reversals of the wind directionalong the shores of the Indian Ocean, especially in the Arabian Sea, that blow from thesouthwest during one half of the year and from the northeast during the other half.[8]
Colin Stokes Ramage in Monsoon Meteorology, International Geophysics Series, Vol. 15,defines Monsoon as a seasonal reversing wind accompanied by corresponding changes inprecipitation.[9]
Monsoon of the subcontinent is primarily noted for its rain bearing ability and for the associatedunpredictability of the weather. Consequently, some definitions incorporate rain in its definition.[10]
Background [ edit ]
Observed initially by sailors in the Arabian sea[11] traveling between Africa, India and South-EastAsia, Monsoon is a major weather phenomenon in India (and the subcontinent) for the influence itcasts on the lives of its inhabitants for centuries. Monsoon in India can be categorized into twobranches based on their spatial spread over the sub-continent:
Arabian Sea Branch
Bay of Bengal Branch
Alternatively, it can be categorized into two segments basedon the direction of rain bearing winds:
South-West Monsoon (SW Monsoon)
North-East Monsoon (NE Monsoon)[Note 1]
Based on the time of the year that these winds bring rain to
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SW Monsoon clouds over TamilNadu
India, they can also be categorised in two rain periods called:
the Summer monsoon (May to September)
the Winter monsoon, (October to November)
The complexity of Monsoon as a weather phenomenon ofIndia is not yet completely understood, making it difficult to accurately predict its behavior in termsof quantity, temporal and spatial distribution of the accompanying precipitation. These are themost monitored components of Monsoon determining the water availability in India for any givenyear.[12]
Mechanism of Monsoon [ edit ]
Monsoon is a tropical phenomenon.The Indian subcontinent liesnorthwards of the equator up to theHimalayas and Hindukush, primarily inthe tropical zone of the NorthernHemisphere.
The weather pattern involves windsblowing from the south-west direction(known as the South-West Monsoon)from the Indian Ocean onto the Indianlandmass during the months of Junethrough September. These aregenerally rain-bearing winds, blowingfrom sea to land, and bring rains to
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Monsoon over India
most parts of the subcontinent. Theysplit into two branches, the ArabianSea Branch and the Bay of BengalBranch near the southernmost end ofthe Indian Peninsula. They are eagerly awaited in most parts of India for their agricultural andeconomic importance.
Subsequently later in the year, around October, these winds reverse direction and start blowingfrom a north-easterly direction. Given their land to sea flow, from subcontinent onto the IndianOcean, this system carries less moisture and brings rain to only limited parts of India like Kerala,Andhra Pradesh and Tamil Nadu. This is known as the North-East Monsoon. However, this rain isresponsible for the rice bowls of South India. This mechanism completes the annual Monsooncycle of the Indian subcontinent.
Main article: Monsoon § South Asian Monsoon
Effect of Geographical relief features [ edit ]
Although the SW and NE Monsoon winds are seasonally reversible, they do not cause precipitationon their own.
Main article: Rain § Formation
Two factors for rains are essential for rain formation:
1. Moisture-laden winds
2. Droplet formation
Main article: Orographic lift
Additionally, one of the causes of rain need to happen, which in this case is primarily Orographic
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due to presence of highlands right across the paths of the winds. Orographic barriers in the pathof a wind force it to rise. Consequently, precipitation occurs on the windward side of highlands dueto adiabatic cooling and condensation of the rising motion of the moist air.
For all the above scenarios to fulfill simultaneously, the unique geographic relief features of Indiansubcontinent come into play. The notable features of Indian sub-continent, required in explanationof the Monsoon mechanism, are as follows:
1. First is the presence of abundant water bodies around the subcontinent - Arabian Sea, Bayof Bengal and Indian Ocean. These help in accumulation of moisture in the winds during thehot season.
2. Second is the presence of abundant highlands like the Western ghats and the Himalayasright across the path of the SW Monsoon winds. These are the main cause of thesubstantial orographic precipitation all over the Indian subcontinent.[Note 2]
1. The Western Ghats are the first highlands of India that the SW Monsoon windsencounter.[Note 3] The Western Ghats rise very abruptly from the Western CoastalPlains of the subcontinent making effective orographic barriers for the Monsoonwinds.
2. The Himalayas play more than the role of just the orographic barriers for Monsoon.They help in its confinement onto the subcontinent. Without it, the SW Monsoonwinds would blow right over the Indian subcontinent into Tibet, Afghanistan andRussia without causing any rain. [Note 4]
3. For NE Monsoon, the highlands of Eastern Ghats play the role of orographic barrier.
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Pink arrow: SWMonsoon wind direction;Green arrow: NEMonsoon wind direction.
Orographic precipitation.
Geographical features ofIndian subcontinent.
Daytime scene showingthe pre-monsoon air overIndia.
Recent trends in totalaverage annualprecipitation frommonsoons
Features of Monsoon Rains [ edit ]
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Monsoon Burst over Mumbai
There are some unique features about the rains that Monsoon brings to the Indian subcontinent.
"Bursting" of Monsoon Rains [ edit ]
Bursting of Monsoon implies the onset of the suddenchange in weather conditions in India (typically from hotand dry weather to wet and humid weather during the SWMonsoon) due to abrupt rise in the mean dailyrainfall.[13][14] Similarly the burst of NE monsoon marks anabrupt increase in the mean daily rainfall over the affectedregions.[15]
Monsoon Rain Variability ("Vagaries") [ edit ]
One of the most commonly used phrases to describe theerratic nature of the Monsoon of the Indian subcontinent is "vagaries of monsoon", used innewspapers,[16] magazines,[17] books,[18] web-portals[19] to insurance plans[20] and India's budgetdiscussions.[21] In some years, it rains too much causing floods in several parts of India, in others itrains too little or not at all causing droughts. In some years when the rain quantity is sufficient, itstiming may be arbitrary. In some years, in spite of average annual rainfall, its daily distribution orthe areal distribution might be substantially skewed. Such is the variability in the nature ofMonsoon rains and weather. In the recent past, rainfall variability in short time periods of about aweek were even attributed to desert dust over the Arabian Sea and west Asia Link .
Ideal and Normal Monsoon Rains [ edit ]
Every year the normal onset of SW Monsoon is expected to
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Annual Average Rainfall Map ofIndia
Every year the normal onset of SW Monsoon is expected to"burst" onto the western coast of India (nearThiruvananthapuram) around 1 June covering entire India byaround 15 July.[12][22][23] Its withdrawal from India typicallystarts from 1 September onwards and completes by around 1October.[24][25]
Similarly the NE Monsoon is expected to "burst" around 20October and last for a period of about 50 days beforewithdrawing.[15]
However, a rainy Monsoon is not necessarily a normalMonsoon. A normal Monsoon is expected to perform close toits statistical averages calculated over a significantly longperiods. Therefore, a normal Monsoon is generally acceptedto be the Monsoon that has near average quantity of precipitation over all the geographicallocations (mean spatial distribution) under its influence and over the entire expected time period ofits influence (mean temporal distribution). Additionally, the arrival date and the departure date ofboth the SW and NE Monsoon should be close to the mean dates. The exact criteria for NormalMonsoon is defined by the Indian Meteorological Department with calculations for the mean andstandard deviation for each of the aforesaid precipitation variables.[26]
A Monsoon with excess rain can cause floods in, and one with too little rain can lead to widespreaddrought, food shortage, famine and economic losses. Therefore, a normal Monsoon with meanperformance is the most desirable Monsoon.
Theories for Mechanism of Monsoon [ edit ]
Theories for mechanism of Monsoon primarily try to explain the reasons for the seasonal reversal
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A: Sea breeze, B: Land breeze
of winds and the timings of their reversal.
Traditional Theory [ edit ]
Main article: Sea breeze
Due to difference in the specific heat capacity of land and water, continents heat up faster than theseas. Consequently, the air above the coastal lands heats up faster than air above seas. Thiscreates areas of low air pressure above coastal lands compared to the air pressure over the seascausing winds to flow from the seas onto the neighboring lands. This is known as sea breeze
Process of Monsoon creation [ edit ]
Main article: Monsoon § Process
Also known as the thermal theory or the Differential Heating ofSea and Land Theory, it portrays the Monsoon as a large-scale sea breeze. It states that during the hot sub-tropicalsummers, the massive landmass of Indian Peninsula heats upat a different rate than the surrounding seas resulting in apressure gradient from South to North. This causes flow ofmoisture laden winds from sea to land. On reaching the landthese winds rise up due to the geographical relief, coolingadiabatically and leading to orographic rains. This is thesouthwest monsoon. Reverse happens during winter whenthe landmass is colder than the sea establishing a pressuregradient from land to sea. This causes the winds to blow overIndian landmass towards Indian Ocean in a north-easterlydirection causing the northeast monsoon. Since the SW monsoon is from sea to land, it has more
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The Atmospheric Circulation system withassociated pressure belts and latitudes
moisture (therefore causing more rain) than the NE monsoon. Only a part of the NE monsoonpassing over Bay of Bengal picks up moisture causing rain in Andhra Pradesh and Tamil Naduduring the winter months.
However many meteorologists argue that the Monsoon is not a local phenomenon as explained bythe traditional theory but a general weather phenomenon along the entire tropical zone of earth.This criticism, does not deny the role of differential heating of sea and land in generating monsoonwinds but merely restricts it to one of the several factors rather than the only one.
Dynamic Theory [ edit ]
Main article: Prevailing windsMain article: Atmospheric circulation
The prevailing winds of the atmosphericcirculation arise due to the difference inpressure at various latitudes of Earth and actas means for distribution of thermal energy onthe planet. This pressure difference is due tothe differences in Solar insolation received atdifferent latitudes of Earth and the resultinguneven heating of the planet. Alternating beltsof high-pressure and low-pressure developalong the equator, the two tropics, the Arcticand Antarctic circles and the two polar regionsgiving rise to the Trade winds, Westerlies andthe Polar easterlies. However, the geophysicalfactors like revolution of earth, its rotation and axial tilt of the Earth result in gradual shifting of
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these belts northwards and southwards following the Sun's seasonal shifts.
Process of Monsoon creation [ edit ]
The dynamic theory of Monsoon explains monsoon on the basis of the annual shifts in the positionof global belts of pressure and winds. According to it, Monsoon is the result of the shift of the InterTropical Convergence Zone (ITCZ) under the influence of the vertical sun. Though the meanposition of the ITCZ is taken as the equator it keeps shifting northwards and southwards with themigration of the vertical sun towards the tropics (Tropic of Cancer and Tropic of Capricorn) duringthe summer of the respective hemispheres (Northern and Southern Hemisphere). As such, thetheory states that during the northern Summer (months of May and June), the ITCZ movesnorthwards, along with the vertical sun, towards the Tropic of Cancer. The ITCZ being the zone oflowest pressure in the tropical region, is the target destination for the Trade winds of both thehemispheres. Consequentially, with ITCZ at the Tropic of cancer, the South East Trade winds ofthe Southern Hemisphere have to cross the equator to reach the ITCZ.[Note 5] However, due toCoriolis effect, (Coriolis effect causes winds in northern hemisphere to turn to its right whereaswinds of southern hemisphere to turn to its left) these South East trade winds are deflectedeastwards in the Northern Hemisphere transforming into South West trades.[Note 6] These pick upthe moisture while traveling from sea to land and cause orographic rain once they hit the highlandsof the Indian Peninsula. This results in the South-West Monsoon.
The dynamic theory provides the explanation of the system of Monsoon as a circum-globalweather phenomenon rather than just a local one. And when coupled with the Traditional Theory(based on heating of Sea and Land) it enhances the explanation of the differential intensity ofprecipitation impact of Monsoon along the coastal regions with orographic barriers.
Jet Stream Theory [ edit ]
Main article: Jet stream
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Jet streams of Earth
The Tibetan Plateau lies north of theHimalayas
Main article: Jet stream
This theory tries to explain the establishmentof both the NE and SW Monsoons as well theirunique features like bursting and variability.The jet streams are a system of upper-airwesterlies. It gives rise to slowly movingupper-air waves, with 250 knots winds in someair streams. First observed by World War IIpilots, they develop just below the tropopauseover areas of steep pressure gradient on thesurface. The main types are the polar jets, the subtropical westerly jets and the less commontropical easterly jets. They follow the principle of geostrophic winds.[Note 7]
Process of Monsoon creation [ edit ]
Over India, a subtropical westerly jet develops in thewinter season which is replaced by the tropicaleasterly jet in the summer season. The hightemperature over the Tibetan Plateau, as well as overCentral Asia in general, during the summer is believedto be the critical factor leading to the formation of thetropical easterly jet over India in summer. Themechanism affecting monsoon is that the westerly jetcauses high pressure over northern parts of thesubcontinent during the winter. This results in thenorth to south flow of the winds in the form of the NEMonsoon. With the northwards shift of the vertical sun, this jet shifts northwards too. The intense
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heat over the Tibetan Plateau, coupled with associated terrain features of high altitude of theplateau, etc. generate the tropical easterly jet over central India. This jet creates a low pressurezone over the northern Indian plains influencing the wind flow towards these plains, assisting theestablishment of the SW Monsoon.
Theory for "Bursting" of Monsoon [ edit ]
The unique feature of bursting[13] of the Monsoon is primarily explained by the Jet Stream theoryand the Dynamic Theory.
Dynamic Theory [ edit ]
According to this theory, during the summer months of Northern Hemisphere, the ITCZ shiftsnorthwards pulling the SW Monsoon winds onto the land from the sea. However the hugelandmass of the Himalayas continue to restrict the low pressure zone onto the Himalayas itself. It isonly when the Tibetan Plateau heats up a lot more than the Himalayas does the ITCZ abruptly andswiftly shift northwards leading to burst of Monsoon showers over the Indian subcontinent. Thereverse shift takes place for the NE Monsoon winds leading to a second minor burst during theNorthern Hemisphere winter Months of NE Monsoon rainfall over Eastern Indian peninsula.
Jet Stream Theory [ edit ]
According to the theory the onset of SW Monsoon over Indian subcontinent is driven by the shift ofthe subtropical westerly jet northwards from over the plains of India towards the Tibetan Plateau.This shift is due to the intense heating of the Plateau during the summer months. This shift of thewesterly jet to the north of the Himalayas is not a slow and gradual process, as expected for mostchanges in weather pattern. The primary cause of these is believed to be the height of theHimalayas. As the Tibetan Plateau heats up the low pressure created over it pulls the westerly jet
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northwards. Due to lofty Himalayas, the westerly jet is inhibited from moving northwards. However,with continuous dropping pressure, sufficient force is created for the movement of the westerly jetacross the Himalayas after a significant period. As such, the shift of the jet is sudden and abruptcausing the bursting of SW Monsoon rains onto the Indian plains. The reverse shift happens forthe NE Monsoon.
Theories for Monsoon Variability [ edit ]
The Jet Stream effect [ edit ]
The above-mentioned Jet Stream theory also explains the variability in timing and strength of theMonsoon.Timing: A timely northward shift of the subtropical westerly jet in the beginning of the summerseason is critical to the onset of the SW Monsoon over India. If the northward shift of this jet isdelayed, so is the SW Monsoon. An early shift heralds in an early Monsoon.Strength: Additionally, the strength of the SW Monsoon is determined by the strength of theeasterly tropical jet over central India. A strong easterly tropical jet results in a strong SW Monsoonover central India and vice versa.
El Niño-Southern Oscillation (ENSO) effect [ edit ]
Main article: El Niño-Southern Oscillation
El Niño is a 'warm' ocean current originatingalong the coast of Peru that replaces theusual 'cold' Peru or Humboldt Current. Thiswarm surface water reaching towards thecoast of Peru with El Niño is pushed
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Effects of El Niño on weather of subcontinent
westwards by the trade winds thereby raisingthe temperature of the southern PacificOcean. A reverse condition is known as LaNiña.
Southern Oscillation, a phenomenon firstobserved by Sir Gilbert Thomas WalkerDirector-General of Observatories in India,refers to the seesaw relationship ofatmospheric pressures between Tahiti andDarwin, Australia.[27] He noticed that when itwas high pressure in Tahiti, it was lowpressure in Darwin and vice versa.[27] ASouthern Oscillation Index (SOI),based on thepressure difference between Tahiti and Darwin, has been formulated by the Bureau ofMeteorology (Australia) to measure the strength of the Oscillation.[28] Walker noticed that thequantity of rainfall in the Indian subcontinent was often negligible in the years of high pressure atDarwin (and low pressure at Tahiti). Conversely, low pressure at Darwin bode well for theprecipitation quantity in India. Thus he established the relationship of Southern Oscillation withquantities of Monsoon rains in India.[27]
Ultimately, it was realized that the Southern Oscillation is just the corresponding atmosphericcomponent of the El Niño/La Niña effect (which happens in the Ocean).[27] Therefore, in thecontext of the Monsoon, the two cumulatively came to be known as the ENSO. The ENSO is knownto have a pronounced effect on the strength of SW Monsoon over India with the Monsoon beingweak (causing droughts in India) during the El Niño years whereas La Niña years had particularlygood Monsoon strength over India.[27]
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Indian Ocean Dipole effect [ edit ]
Main article: Indian Ocean Dipole
Although ENSO was statistically effective in explaining several past droughts in India, in the recentdecades the ENSO-Monsoon relationship seemed to weaken in the Indian subcontinent.[29] Forexample, the 1997, strong ENSO failed to cause drought in India.[27] However, it was laterdiscovered that just like ENSO was an event in the Pacific Ocean, a similar seesaw ocean-atmosphere system in the Indian Ocean was also at play. It was discovered in 1999 and named theIndian Ocean Dipole (IOD). An index to calculate it was also formulated. IOD develops in theequatorial region of Indian Ocean from April to May peaking in October.[27] With a positive IODwinds over the Indian Ocean blow from east to west. This results in the Arabian Sea (westernIndian Ocean near African Coast) being much warmer and eastern Indian Ocean around Indonesiabecoming colder and dry.[27] In the negative dipole year, reverse happens making Indonesia muchwarmer and rainier. It was demonstrated that a positive IOD index often negated the effect ofENSO, resulting in increased Monsoon rains in several ENSO years like the 1983, 1994 and1997.[27] Further, it was shown that the two poles of the IOD - the eastern pole (around Indonesia)and the western pole (off the African coast) were independently and cumulatively affecting thequantity of rains for the Monsoon in the Indian subcontinent.[27]
Equatorial Indian Ocean Oscillation [ edit ]
Similar to ENSO, the atmospheric component of the IOD was later discovered and named asEquatorial Indian Ocean Oscillation (EQUINOO).[27] When EQUINOO effects were factored into thestatistics certain failed forecasts, like the acute drought of year 2002, could be further accountedfor.[27] The relationship between extremes of the Indian summer monsoon rainfall, along with ENSOand EQUINOO[30] have been studied and models for enhanced predictability of the quantity ofmonsoon rains have been statistically derived.[30]
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Monsoon Rain prediction models [ edit ]
Since the Great Famine of 1876–78 in India, various attempts have been made to predict therainfall during the Monsoons in India.[31] At least five models for prediction of Monsoon rains existin India.[32]
Seasonal Prediction of Indian Monsoon (SPIM) [ edit ]
Centre for Development of Advanced Computing (CDAC) at Bengaluru is facilitating the SeasonalPrediction of Indian Monsoon (SPIM) experiment on the PARAM Padma supercomputing system.[33]
This project did simulated runs on historical data from 1985 to 2004 to try and establish therelationship between of five atmospheric general circulation models with the Monsoon rainfalldistribution.[32]
Indian Meteorological Department Model [ edit ]
IMD has tried to forecast the Monsoon for India since 1884,[31] some unsuccessfully but till 2011 isthe only official agency entrusted with making public forecasts about the quantity, distribution andtimings of the Monsoon in India. IMD's position as the sole authority on the matter was furtherreiterated in 2005[32] by the Department of Science and Technology (DST), New Delhi. In 2003,IMD underwent a substantial change in its forecast methodology, model[34] as well as itsadministration.[35] A sixteen parameter monsoon forecasting model used by the Indian met officesince 1988 was revamped in 2003 with a new one.[34] However, following the 2009 drought in India(worst since 1972),[36] IMD decided in 2010 that it needed to develop an indigenous model[37] tofurther enhance its prediction capabilities.
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Western Ghats on 28 May in dry season
Western Ghats on 28 August in rainy season
Significance [ edit ]
Indian Monsoon is the primarydelivery mechanism for freshwater in the Indiansubcontinent. As such itimpacts the environment (andassociated flora, fauna andecosystems), agriculture,society, hydro-powerproduction and geography ofthe subcontinent (likeavailability of fresh water inwater bodies, undergroundwater table) with all thesefactors cumulativelycontributing towards thehealth of the economy of affected countries.
The Indian Monsoon turns large parts of India from a kind of semi-desert into green grasslands.See photos only taken 3 months apart in the Western Ghats.
Geographical (Wettest Spots on Earth) [ edit ]
Mawsynram and Cherrapunji, both in the Indian state of Meghalaya alternate to be the wettestplaces on Earth given the quantity of their rainfall.[38] There are other cities with similar claims butwith more than 11,000mm of rain for each of these locations, Monsoon of Indian subcontinent is a
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significant contributor towards the water supply of its area of influence.
Agricultural [ edit ]
India, historically an agrarian economy primarily, has recently seen the services sector overtakingthe farm sector in terms of GDP contribution. However, even today agriculture sector contributes17-20% of GDP[39] and is the largest employer in the country with about 60% of people dependenton it for employment and livelihood.[39] The land use pattern of India indicates that 49% of land isunder agriculture in India, it is 55% if associated wetlands agriculture, dryland farming areas, etc.are included. Since over half of these farmlands are rain-fed, Monsoon is critical to the foodsufficiency and quality of life for the country. Despite progress in alternative forms of irrigation,agricultural dependency on monsoon is far from insignificant, even today. Therefore, theagricultural calendar of India is governed by Monsoon. Any fluctuations in the time distribution,spatial distribution or quantity of the monsoon rains may lead to conditions of floods or droughtscausing the agricultural sector to adversely suffer. This has a cascading effect on the secondaryeconomic sectors, the overall economy, food inflation and therefore the overall quality and cost ofliving for the general population in India.
Economic [ edit ]
The economic significance of monsoon can be aptly summed up by Pranab Mukherjee's statementthat monsoon is the real finance minister of India.[4][5] A good monsoon resulting in improvedagricultural brings down prices of essential food commodities and reduces their imports overallreducing the food inflation.[39] Further improved rains result in increased hydroelectricproduction.[39] All these factors initiate positive ripple effects throughout the economy of India.[39]
Social [ edit ]
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D. Subbarao (Governor of Reserve Bank of India), during a quarterly review of the monetarypolicy, once highlighted that lives of Indians depends on the performance of Monsoon.[40] His ownpersonal career prospects, emotional well being and the performance of his monetary policy wereall a hostage to monsoon like it was for most Indians.[40] Additionally, farmers, rendered joblessdue to failed Monsoon rains tend to migrate city-wards. This crowds the city slums and furtheraggravates the job, infrastructure and sustainability of city life.[41] Such is the magnitude of effectthat monsoon casts on the lives of Indians.
Travel [ edit ]
In the past, people usually refrained from traveling during monsoons for practical as well asreligious reasons. But with the advent of globalization, travelling during monsoons is gainingpopularity. Places like Kerala and the Western Ghats get a very large number of tourists, bothlocal and foreigners during the monsoon season. Kerala is one of the top destinations for touristsinterested in Ayurvedic treatments and massage therapy. One major drawback of traveling duringthe monsoons is the fact that most wildlife sanctuaries are closed during this season. Also, somemountainous areas, specially in Himalayan regions get cut off due to damaged roads caused bylandslides and floods during heavy rains.[42]
Environmental [ edit ]
The Monsoon is the primary bearer of fresh water to bodies of water in the area. Thepeninsular/Deccan rivers of India are mostly rain-fed and non-perennial in nature dependingprimarily on the Monsoon for water supply.[43] Similarly most of the coastal rivers of Western Indiaare rain-fed and Monsoon dependent.[43][44] As such, the flora, fauna and the entire ecosystem ofthese areas are heavily dependent on the Monsoon.[citation needed]
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Notes [ edit ]
1. ^ The name of the wind is based on the direction that it blows from. Therefore, South-West windsimply that the winds are blowing onto the land from the South-West direction. Similarly North-Eastwind implies air flowing from north east towards south-west onto the land
2. ^ The Aravalli Mountains also lay in the path of the SW Monsoon but do not result in muchprecipitation because they are in the direction of the path of the SW winds and not across themcausing no orographic lift of the winds
3. ^ Other major highlands like Cardamom Hills, Anaimalai Hills and Nilgiri mountains) playing activeroles in the Monsoon are considered major extensions of the Western Ghats and thus not discussedseparately
4. ^ Firstly, Himalayas serve as orographic barriers to the SW Monsoon Winds. Secondly, they help inthe confinement of Monsoon within the subcontinent region, hampering their northward progress.Thirdly, they help in the convergence of the Bay of Bengal branch and Arabian Sea Branch of theSW Monsoon winds increasing the precipitation intensity over the northern part of the subcontinent.Fourthly they are a major factor in the bursting of Monsoon as per the Jet Stream Theory. Fifth, theyassist in the determination of directionality of the Bay of Bengal branch for NE Monsoon. Their role isstill a matter of active study and our understanding about them is evolving regularly
5. ^ When the South East Trade winds cross the equator, in the northern hemisphere they are alsoperceived as equatorial westerlies since they seem to blowing from the equator towards the Tropic OfCancer. Similarly, due to the ITCZ being at Tropic of Cancer, the North-East Trades are confined tothe north of the Tropic of Cancer
6. ^ Change of direction or origin of winds changes their nomenclature as noted above
7. ^ Geostrophic winds blow parallel to the isobars and keep low-pressure zone to their left in theNorthern Hemisphere and to the right in the Southern Hemisphere. The reversal is a result of theCoriolis effect.
See also [ edit ]
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Weather portal
India portal
Monsoon
North American Monsoon
Monsoon trough
Climate of India (section Monsoon)
Asian brown cloud
Tropical monsoon climate (section Factors)
Tibetan Plateau (section Role in monsoons)
Himalayas (section Impact on climate)
Prevailing winds
Jet Stream
Rain
Walker circulation
Indian peninsula
Indian Meteorological Department
Drought in India
Andhra Pradesh (section of Geography and climate)
Monsoon (section of South Asian Monsoon)
References [ edit ]
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43. a b "Rivers-Profile-Know India" . India.gov.in. Archived from the original on 2011-02-04. Retrieved6 March 2011.
44. ^ "Indian Geography" . IndiaBook.com. Retrieved 6 March 2011.
External links [ edit ]
Indian Meteorological Department Official Website
Centre for Development of Advanced Computing
Monsoon On-Line, an Indian Institute of TropicalMeteorology, Pune, India initiative
Geography of India
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