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Monsoon has turned normal, IMD says. But it really hasn’t if you see regional variations

While heavy rains have lashed parts of Assam and Meghalaya in the northeast, planting of rain-fed kharif crops has been delayed in Odisha, where the rain deficit is 39%.

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New Delhi: After a slow start, the four-month-long Southwest monsoon has finally turned normal, data from the India Meteorological Department (IMD) shows.

Compared to a 42 per cent deficit in rainfall recorded on 8 June, the monsoon entered normal territory Tuesday at 98 per cent of the long period average (LPA) — rainfall recorded over a particular region during a given period.

According to the IMD’s long-range forecast issued on 31 May, seasonal rainfall over India is likely at 103 per cent of the LPA, which is 87 cm for the 1971-2020 period).

A normal monsoon is crucial since the June-September season irrigates more than half of India’s kharif crop in areas that lack assured irrigation.

However, even as the monsoon advances over the southern, central and northeastern regions, rainfall patterns show a wide variation across states.

Heavy rains have lashed parts of Assam and Meghalaya in the northeast, while planting of rain-fed kharif crops has been delayed in Odisha, where the deficit is 39 per cent.

IMD Director General Mrutyunjay Mohapatra said that these variations are already moderating, with time still left for the monsoon to set in across the northwest.

“The rainfall is already reducing in the northeast region, and the monsoon is now beginning in the central region,” he told ThePrint, adding that the IMD expects the monsoon to “proceed as we have projected”.

While variations at the onset of monsoon are typical, the downpour over the northeast — classified as an extreme weather event — has made the difference starker.

On 21 June 2021, central India had a 58 per cent deficit in rainfall, while the deficit was 13 per cent for the northeast. This year, the northeast region is witnessing excess rainfall to the tune of 43 per cent, while the central region is seeing a deficit of 33 per cent.

Illustration by ThePrint team
Illustration by ThePrint Team

“The problem with an overall projection is that it averages out the floods in the east with the droughts or dry conditions in the west,” said Roxy Koll, a scientist with the Centre for Climate Change Research at the Indian Institute of Tropical Meteorology (IITM) in Pune.

“Regional departures from the norm give us a more accurate picture of monsoon conditions within the country,” Koll added.


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What caused the deluge

The sudden downpour in the northeastern states of Assam and Meghalaya was caused by a host of weather conditions, meteorologists say.

While Meghalaya saw 174 per cent excess rain compared to normal levels, in Assam, rainfall was 97 per cent over normal.

“Strong southwesterly winds from the Bay of Bengal were continuously feeding moisture over the northeastern part of the country. A cyclonic system was also persisting over Bangladesh and other adjoining areas, which caused heavy rainfall in the region,” said Mahesh Palawat, vice-president of meteorology and climate change at private forecaster Skymet Weather.

India is also impacted by two other natural global weather events that exacerbated the monsoon in the northeast: La Nina (a weather phenomenon involving fluctuating ocean temperature “in the central and eastern equatorial Pacific, coupled with changes in the atmosphere”, which affects climate patterns in different parts of the world) and a negative Indian Ocean Dipole (when waters near the eastern Indian Ocean are warmer than normal).

“Sometimes these phenomena create unfavourable conditions for the monsoon, as we are seeing right now. This type of variation can happen from year to year, where some years have favourable conditions and others are unfavourable,” said J.R. Kulkarni, a retired scientist from IITM.

Rajib Lochan Deka, associate professor at Assam Agricultural University, studied rainfall patterns in Assam from 1988 to 2018 and found an overall decrease in the amount of rainfall over the state, as well as a decrease in the number of extreme rainfall days.

The sudden bout of rain this time — unusual in recent years — has led to widespread damage, causing landslides, and killing at least 82 people.

“The summer vegetables have been completely damaged. Generally, the transplanting of kharif rice, the predominant crop of Assam, starts from the second fortnight of June and continues till the end of July, particularly in the western parts of Assam. As the rice nurseries have been damaged by floodwater, there might be a shortage of rice seedlings for normal transplanting,” Deka told ThePrint.

Impact of climate change

The extreme rainfall in Assam and Meghalaya has occurred in a warming climate.

Extreme weather events from time to time are natural, but the likelihood of extreme rainfall in India will only rise in the decades to come, the Intergovernmental Panel on Climate Change (IPCC) has warned.

A study by Koll, who is also an IPCC author, found that India witnessed a threefold increase in extreme rainfall events after the 1950s — a likely consequence of global warming.

Global temperatures have shot up by 1.1 degree since 1850 (pre-industrial times). Every one-degree rise in temperature brings with it a 7 per cent increase in moisture, causing more extreme rainfall patterns in South Asia, the latest IPCC report found.

“Generally, with global warming, warm air will hold more moisture for a longer time. So, there are spells when it doesn’t rain for a long time, but when it does, it dumps all that moisture within a few hours or days, causing extreme rainfall,” Koll said, adding, “What we’re seeing in India is that the monsoon is not well spread.”

(Edited by Amrtansh Arora)


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