As the southwest monsoon gets ready to begin its retreat, the central India region — comprising two of the country’s largest states, Madhya Pradesh and Uttar Pradesh — appears likely to remain rainfall-deficient this season.
Meteorologists are pointing to climate change for this season’s erratic rainfall. There were several instances of very heavy rainfall over small areas with relatively prolonged dry periods in between. As a result, there was severe flooding over Assam in the Northeast, Bihar and West Bengal in the East, and Gujarat and Rajasthan in the West during July and August.
Rainfall data until September 12 by the India Meteorological Department (IMD) show that Central India was rain-deficient by 10 per cent, the highest among the broad regions of the country. At the state level, Goa, Delhi, Haryana and Nagaland have seen deficiencies ranging between 23% and 43% so far.
This is a contrast from the situation last year, when Central India, Madhya Pradesh in particular, had received 19% excess rainfall. There are similar variations from last year in some other meteorological subdivisions, too. Vidarbha, for example, is short by 27% rainfall at present; last year, it had 10% surplus at the end of the season.
An increase in the frequency of extreme rainfall events has been a trend worldwide, and meteorologists at IMD said this year’s monsoon was a very good example of this global trend.
“This year, rainfall was largely localised rather than being distributed over a region. Heavy rains occurred in a short period of time, within two to four days, which was followed by a prolonged dry spell over the same region,” said D Sivananda Pai, head, climate research division at IMD. “This is a typical break-monsoon type, attributed to be one of the features associated with climate change.”
At the start of 2017, international weather models had been showing the possibility of a weak El Niño developing towards the latter half of the year, but that has not happened. Scientists said, however, that the monsoon trough largely remained hovering over the Himalayan foothills, affecting precipitation over Central India.
The resultant dry spell, experienced mainly in the crucial month of August over Central India, could have been under the influence of active wind systems over the Pacific Ocean. According to Japan Meteorology Agency (JMA), there have been close to 30 weather systems including storms emanating from the Pacific Ocean. Usually, the number is around 15 to 20 between March and October.
“Despite the absence of factors like El Niño that could have interfered with Indian monsoon in some manner, the monsoon came under the influence of an active Pacific Ocean and was thereby weakened post July,” Pai said. “That resulted in a long dry spell during most of August and early September too. The moisture from over the Indian landmass was all attracted towards the West Asian regions, leaving Central India with below-normal rainfall.”
The Arabian Sea, on the other hand, has not supported enough moisture accumulation, leaving parts of the west coast — Goa and coastal Karnataka, otherwise wet areas — devoid of the rainfall it usually receives.
“This was because of lack of moisture incursion from the Arabian Sea as the monsoon winds largely skirted the west coast for most of this season. Kerala and south interior Karnataka, which were continuing to remain in the deficient categories, have received rainfall as late as September,” said a senior official at IMD, Pune.