IMD to announce new dates for exit, onset of monsoon
The monsoon rains are critical because nearly half the population depends on a farm-based income and 60% of the country’s net sown area does not have any form of irrigation.
The India Meteorological Department (IMD) is set to announce new dates for the onset and withdrawal of the south-west monsoon this year, a government official and the weather department said on Wednesday, in a move that could affect millions of farmers who depend on the rainy season for a bumper yield of kharif crops.
The normal monsoon onset date over Kerala is June 1, and the withdrawal date is September 30, according to IMD. These dates are based on the monsoon pattern between 1901 and 1940, but India has recorded significant shifts in the pattern over the past decades, M Rajeevan, secretary in the ministry of earth sciences, said at IMD’s 145th foundation day on Wednesday.
“Over Kerala, it [monsoon] has not changed much, but over many other places, it has changed. It is either arriving early or late in some regions. For example, over central India it’s arriving late. Withdrawal is almost 10 days late over north-west India now. Total period of monsoon is same, but it’s coming late and going late. This change will affect farmers. They will have to change their strategy,” Rajeevan said.
IMD director general, M Mohapatra, said the new dates will be announced in April, and will apply from this year.
Rajeevan pointed out that the changed dates were recommended by meteorologists in the past as well, but they never got IMD’s approval. “IMD didn’t want to possibly attribute it to climate change, though they knew things were changing. People accept climate change now. I insisted that dates should be changed. We cannot use the climatology of the 1940s to inform people, it’s a little awkward,” he said.
Rajeevan, however, said it was not possible to immediately link the changes in monsoon dates to the climate crisis; it could be a change in monsoon cycle also.
The monsoon rains are critical because nearly half the population depends on a farm-based income and 60% of the country’s net sown area does not have any form of irrigation. Millions of farmers wait for the rains to begin summer sowing of major staples, such as rice, sugar, cotton, coarse cereals and oilseeds. Half of India’s farm output comes from summer crops, or kharif crops, dependent on the rains.
According to IMD, the four-month monsoon season normally begins retreating on September 1, and withdraws from the north-west, central and eastern parts of the country by October 15. The peninsular region receives rains again when the northeast monsoon commences around mid-October.
In 2019, according to IMD, the south-west monsoon started withdrawing on October 9. The weather department said it was the most delayed withdrawal in the past 58 years (since 1961). Last year, the onset happened on June 8. The month ended with a rain deficiency of 33%, while July, August and September received 105%, 115% and 152% rains of their Long Period Average (LPA) respectively.
“2019 was a year of extremes. There was severe heat wave in the east... excess monsoon ending with 110% of LPA. The post-monsoon season saw some serious cyclonic activity... From December 15 to 31, we saw a very severe cold spell in north India,” said Mohapatra.
DS Pai, a senior scientist from IMD Pune, who recently submitted a report to the weather department on changes in monsoon pattern, said: “Our dates were based on data from 1940s, and only from 149 weather stations. Now there is climate change. We want to document what has changed. Agricultural policies and practices are impacted by these dates.”
Krishna Achuta Rao, a professor of atmospheric sciences at the Indian Institute of Technology, Delhi, said, “My sense is that they are changing what is supposed to be normal. It is a recognition that normals have changed in the past decades because the data used to record onset and withdrawal is very old -- from the ’40s. For the weather community, this is a very important development.”
IMD also announced that it will soon issue impact-based forecasts wherein the weather department will inform state governments about what to expect from an extreme weather event to help them prepare better. This system is being developed with help from the UK Meteorological Department.
