RECENT TRENDS IN INDIAN MONSOON

Changing Monsoon pattern in India

Monsoon
The seasonal reversal of wind direction during a year accompanied by corresponding changes in
precipitation. The monsoon or southwest monsoon is a sea-breeze from the Arabian Sea and the Bay
of Bengal that officially onsets over Kerala on June 1 and retreats from Rajasthan by the end of
September. It is then replaced by the retreating, or northeast monsoon in November which is the key
source of rainfall for several parts of Tamil Nadu, Andhra Pradesh and north interior Karnataka.
Changing monsoon patterns
 Surplus precipitation: Central and southern India saw a sharp surge in rainfall. Rains in Central
India were surplus by 20% and in southern India by 25%, with the last month seeing several
instances of flooding in Kerala, Karnataka and Madhya Pradesh.
 Deficit: On the other hand, large parts of U. P., Bihar, Odisha have seen large deficits. The east
and northeast of India have reported a 17% shortfall and the northwest 2%.
 Weakened monsoon circulation: The warming Indian Ocean also plays a role in weakening the
monsoon circulation. Increased warming in the ocean enhances the large-scale upward motion of
warm moist air over the equatorial ocean. This enhanced upward motion over the ocean is
compensated by the subsidence of dry air over the subcontinent, inhibiting convection and rainfall
over the Indian landmass. This means that the warming Indian Ocean has resulted in surplus rains
over the ocean at the cost of the monsoon rains over land, simultaneously drying the Indian
subcontinent.
 Incessant rain over Delhi and several other parts of North and Northwest India over the last few
days provide further evidence of the shifting patterns in monsoon activity over the Indian
subcontinent.
 More intense-Not only has monsoon rainfall become more erratic — fewer rainy days but more
intense rain — the monsoon season, earlier confined neatly to the four-month June-September
period, is clearly spilling over into October now. This has been officially recognised. Three years
ago, the India Meteorological Department (IMD) had revised the expected dates of onset and
withdrawal of the monsoon for several regions of the country.
 The withdrawal dates for North, Northwest and Central India were pushed back by one to two
weeks to account for the trends witnessed over the last 50 years.
 Thus, the October rainfall over North India of the kind that happened over the last few days
should no longer surprise anyone. It should in fact, be increasingly seen as the norm rather than an
exception.
 Delhi and its surrounding areas had received pretty good rainfall in October 2021 as well — so
much so that Delhi had its fourth wettest October of the last 120 years. Considering the huge
amounts of rain that have fallen in the first 10 days of this month — eight times more than the
normal — this October could turn out to be even wetter than last year’s.
Longer rainy season
 In any case, rainfall in October — after the traditional date of withdrawal of the southwest
monsoon — isn’t entirely unheard of. It has happened in several previous years as well. But the
rain in those years was mostly caused by different, often local, atmospheric phenomena.
 What is being witnessed in more recent years is a clear prolongation of the monsoon season. The
nature of rainfall is very different — it is not a short-duration heavy downpour, but sustained rain
over a few days.
 The recent spell of rainfall over Western Uttar Pradesh, Uttarakhand, Haryana, Eastern Rajasthan
and Delhi were a result of the interaction of monsoon winds, moving east to west, with the
western disturbance wind system.
 Such interactions happen several times during the monsoon season.

Climate change is responsible for changing monsoon in India

 Like most of the changes being witnessed in global weather patterns, the changing trends in the
Indian monsoon are also being driven primarily by climate change. In line with the experience in
many other parts of the world, rainfall in India is increasingly taking place in short, intense
bursts. Extreme rainfall events are increasing both in intensity and frequency. The extension of the
monsoon season could also be seen as a consequence of global warming.
 A robust study to establish the cause and effect relationship is yet to be done, but one possible
reason for the spillover of monsoon rainfall to October could be the fact that the oceans (Bay of
Bengal and Arabian Sea) are now warmer than earlier.
 Warmer ocean currents help the formation of monsoon winds. Earlier, rainfall during the
monsoon season would bring down the temperature of the ocean. But possibly because of global
warming, the oceans continue to remain warm even after the traditional monsoon season is
over. The oceans could thus be playing a role in keeping the monsoon alive beyond the traditional
period,” Rajeevan said.
 Global warming is affecting rainfall patterns in other ways too. A warmer atmosphere has a
greater capacity to hold water. When this water is finally released, it often results in a heavier
downpour than would be expected otherwise. This accounts in part for the increasing instances of
extreme rainfall events.
 Persistence of intense La Nina conditions, the abnormal warming of East Indian Ocean,
negative Indian Ocean Dipole (IOD), southward movement of most of the monsoon depressions
and lows and pre-monsoon heating over the Himalayan region and melting glaciers. Triple dip’
 La Nina: India is seeing an extended spell of the La Nina, called a ‘triple dip’ La Nina which is a
phenomenon lasting across three winter seasons in the northern hemisphere.

Impact on of changing pattern on different sectors

 Monsoon rainfall is not just a weather phenomenon. It is a key driver of the Indian economy.
 Indian agriculture still depends on monsoon rainfall for irrigation. One of the major impacts of
changes in track of monsoon systems can be seen on kharif crops, particularly rice
production. The uneven distribution of rain may impact the quality of the grain as well as the
nutrition value may vary.
 Study- ‘Climate change, the monsoon, and rice yield in India’, very high temperatures (> 35°C)
induce heat stress and affect plant physiological processes, leading to spikelet sterility, non-viable
pollen and reduced grain quality. Not just the preferred time of sowing of crops, but the entire
cropping cycle — even the choice of crops — might need to be changed.
 The supply of drinking water and the generation of electricity are also linked to the monsoon.
 Dams-There are implications for dam management as well. Most reservoirs in the northern and
central parts of the country seek to attain full capacity levels by the end of September because not
much rain is expected after that. But if the monsoon consistently spills over into October, as is
being predicted, this practice would need to be revised as well.
 The other sectors are yet to react to the change in monsoon calendar that was announced by the
IMD three years ago, but it will not be long before they are forced to respond.

Way forward
 Forecasting-There is a need to set up more observation stations, collect more data, and do more
computing. Capacity upgradation has to be a continuous exercise.
 With a warming climate, more moisture will be held in the atmosphere, leading to heavier rainfall,
consequently, inter-annual variability of the monsoon will increase in future. The country needs to
prepare for this change.
 Need to take effective and timely steps not just at the domestic front (National Action Plan on
Climate Change) but also at the international front (UN Framework Convention on Climate
Change).
 The current atmospheric carbon dioxide (CO2) concentrations are higher than at any time in the
last two million years. To align with a 1.5°C target of limiting warming, global CO2 emissions
must reach net zero around 2050, with global GHG emissions reaching net-zero 15-20 years later.

REFERENCES:
https://journalsofindia.com/changing-monsoon-pattern-in-india/
https://www.indiatoday.in/environment/story/climate-change-altered-2024-monsoon-study-
warns-of-increasing-weather-extremes-2618540-2024-10-17
https://www.climate.rocksea.org/research/warm-ocean-weak-monsoon/