NEW DELHI :
After a detailed review lasting months, the India Meteorological Department (IMD) has announced that it would introduce new dates for the normal onset and withdrawal of the south-west monsoon this April.
“The report is almost ready, and we will implement the changes from this monsoon season, starting June. While there would be no change in the normal date of onset over Kerala (June 1), the dates when monsoon would be expected to reach different parts of the country could change. The new dates would be announced meteorological station-wise," said M. Rajeevan, Secretary, Ministry of Earth Sciences.
While there may not be “drastic" changes in the onset dates, with only a difference of few days, a major change can be expected in the withdrawal dates. Out of the four divisions, maximum changes have been observed over Central India, the core monsoon region.
The south-west monsoon which provides over 75% of the annual rainfall over India has been consistently arriving late and taking longer time to withdraw from different parts of India. As a result, rains are spilling over to mid-October, delaying the harvesting of Kharif crops like rice.
The trend has been observed since 2010, but was more evident last year, with monsoon recording its longest delayed withdrawal ever, beginning its retreat on October 8. The onset too was delayed in most parts, with Mumbai not receiving rains until June 25, a delay of nearly 20 days.
“The most important aspect is ‘withdrawal’, especially from north-east India, where it’s getting delayed by almost ten days now. Though, the total monsoon period (four months-June-September) may still be the same, but farmers would have to change their sowing strategy according to the new dates," said Rajeevan.
According to meteorologists, the changes could be part of a systematic change in the monsoon, which has a large 60-years cycle. and cannot be directly attributed to global warming.
“The fact is that we cannot use the climatology of 1940s for informing people about the weather in 2020. It has been proposed several times in the past, but this time, we decided to implement it," he added.
IMD Director General of Meteorology, M Mohapatra said, the new onset and withdrawal dates would be announced in April, when IMD brings out its first long-range forecast for the monsoon. It would also issue advisories for farmers to help them plan their sowing accordingly.
The four-month south-west monsoon is extremely crucial for India’s economy as it irrigates over 50% of the agricultural land.
Also, while the rainy season may be getting longer, not much change has been seen in the quantum of seasonal rainfall. The average seasonal rainfall was revised from 89 cm during 1950 to 2000 to 88 cm during 1960 to 2010, recording only a slight decrease in last ten years. However, the number of days with heavy rainfall have increased.