October sees more number of heavy rainfall events in last six years

Southwest monsoon period (June-September) witnesses a good number of heavy rainfall events (64.5 mm to 115.5 mm). In the recent years, October is also witnessing a good number of heavy rainfall events.

In fact, heavy rainfall events in October were more than 10 per cent of such events during the entire southwest monsoon period of 2021 and 2022.

Southwest monsoon months witnessed 6,294 and 7,251 heavy rainfall events in 2021 and 2022, respectively. Comparatively, October witnessed 788 and 786 heavy rainfall events during the above-mentioned years, respectively.

Speaking in Parliament recently, the Union Minister of Earth Sciences, Kiren Rijiju, attributed this increase in the number of heavy rainfall events during October to the delayed withdrawal of the southwest monsoon in the country.

Rainfall patterns during the months other than southwest monsoon in India show that number of extremely heavy rainfall (more than 204.5 mm) events went up during May of 2020, 2021, and 2022. India recorded 21 such events in May 2020, 40 in 2021, and 23 in 2022.

Though October topped in terms of extremely heavy rainfall events during 2017, 2018, and 2019, the number of such events was below the May figures of 2020-2022. October figures were at 10 in 2017, 17 in 2018, and 16 in 2019.

In fact, January 2021 witnessed four extremely heavy rainfall events.

Monsoon

Southwest monsoon months of June-September saw more than 7,200 heavy rainfall events in 2019, 2020, and 2022. However, heavy rainfall events were at 5,833 in 2018, and 6,294 in 2021.

Extremely heavy rainfall events were the highest at 502 during southwest monsoon of 2019, followed by 313 in 2020. During the monsoon seasons of 2018, 2021, and 2022, these numbers remained in the range between 276 and 296.

Referring to the rainfall trend during 1989-2018 period, the Minister said many districts in the country have shown significant changes in southwest monsoon and annual rainfall during the period.

According to him, significant increasing trend has been observed with regard to the frequency of heavy rainfall days over Saurashtra and Kutch, southeastern parts of Rajasthan, northern parts of Tamil Nadu, northern parts of Andhra Pradesh and adjoining areas of southwest Odisha, many parts of Chhattisgarh, southwest Madhya Pradesh, West Bengal, Manipur and Mizoram, Konkan and Goa and Uttarakhand.

State-wise distribution

Gujarat and Sikkim received surplus rainfall of 50 per cent or more than the normal rainfall during the southwest monsoon season in 2020. During monsoon 2020, Gujarat received 1091.7 mm of rainfall against the normal rainfall of 692.4 mm; and Sikkim got 2416.3 mm against the normal of 1606.8 mm.

Ladakh, which received 67 per cent deficient rainfall than the normal rainfall during monsoon 2020, received 69 per cent surplus rainfall in 2022.

However, Manipur got deficient rainfall of 47 per cent, 60 per cent and 48 per cent than the normal rainfall during monsoon of 2020, 2021, and 2022, respectively.

Meghalaya, which gets maximum rainfall in India, got deficient than the normal rainfall in 2021 and 2022.

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