August 31, 2021 8:22:49 pm
August this year ended as the seventh most rain-deficient in the last 122 years, with the all-India rainfall 24.1 per cent below normal.
During the entire month, the country recorded only 190.5 mm of rain.
July and August are crucial rainfall months during the four-month-long monsoon season as each accounts for nearly 35 per cent of the season’s rainfall.
However this year, both July and August rainfall recorded over the country were below normal, according to the rainfall data of the India Meteorological Department (IMD). Between June 1 and August 31, the all-India rainfall was 91 per cent of the Long Period Average (LPA), which is 880 mm.
There were multiple factors which led to negative rainfall activity over the country and these kept the overall monsoon activity largely limited to the Himalayan foothills, keeping the northwest, central and peninsular India devoid of normal rainfall.
There were only two low-pressure systems — including the present one, which weakened into a cyclonic circulation and lay over Vidarbha in Maharashtra — which formed in August.
“Normally, there are four such systems that develop in the Bay of Bengal during August, of which two systems intensify into depression and bring good rainfall over the central India region,” D Sivanand Pai, head of Climate Research and Services, IMD Pune, told The Indian Express on Tuesday.
Normally, the typhoons formed in the west Pacific Ocean during the Indian monsoon months travel westwards, bring heavy rain over Myanmar and move further west to re-enter the Bay of Bengal as low-pressure systems.
“These then enter India along the east coast and cause rainfall over the east and central India regions. However, in August this year, most of the typhoons recurved and travelled north-eastwards instead and none reached the Bay of Bengal,” said Pai.
The prevailing negative phase of Indian Ocean Dipole (IOD) is known to cause below normal rainfall over central India, which further hampered the rainfall activity.
In August, central India — which is the Core Monsoon Zone and a rain-fed agriculture region — received only about 60 per cent of the Long Period Average.
Northwest India recorded 70 per cent of the LPA last month. All 34 districts in Gujarat and Kutch-Saurashtra regions ended with deficient rainfall this August. Gujarat is among the driest Indian states this season and has recorded only 55 per cent of its seasonal quota.
Dadra and Nagar Haveli has, however, recorded normal rainfall so far.
With no favourable systems formed in the Bay of Bengal, the monsoon trough remained largely positioned along the Himalayan foothills or to the north of its normal position for most days of last month.
Yet another factor, Pai said, was the weak phase of the Madden Julian Oscillation – eastward propagating winds with periodicity of 30 to 90 days. “It was located over Africa and the west Indian Ocean regions,” added Pai.
As many as 27 of the 30 districts in Odisha are facing severe rainfall deficit as the monsoon season enters the final leg this year, and the state has seen rain deficit of 31 per cent.
Similarly, more than half rain-deficit districts are in Manipur –58 per cent (8 out of 9 districts), Ladakh –51 per cent (both districts) , Chandigarh -38 per cent (only district), Lakshadweep -35 per cent (only district), Jammu and Kashmir -29 per cent (12 out of 20 districts), Meghalaya -28 per cent ( 5 out of 8 districts), Kerala –28 per cent (12 out of 12 districts), Nagaland -25 per cent (7 out of 11 districts) , Arunachal Pradesh –24 per cent (11 out of 16 districts) and Punjab –21 per cent (11 out of 22 districts).
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