At a time when international models suspect that central and equatorial east Pacific is slowly drifting to El Nino conditions, a study on its likely impact on monsoon here has thrown up interesting results.

El Nino has no direct correlation with monsoon performance but has generally been viewed with circumspection since it has conjured up deficit-rain years often in the past.

El Niño years

K Srikanth, a Chennai-based blogger and weather enthusiast, studied monsoon performance in 13 Met subdivisions during El Nino years for a 30-year-period.

He told BusinessLine these subdivisions account for some of the highest precipitation normally during the southwest monsoon and also cover major swathes of the country.

The study, which covered El Nino years between 1982 and 2012, showed that entire Gangetic plain from Bihar to west Uttar Pradesh is seriously impacted by El Nino.

More than seven out of 10 such years resulted in rain-deficit years.

Odisha exception

Odisha to the south-east was relatively immune to El Nino with only two years generating a deficit.

Closely following the plains of northwest and east India were the Met subdivisions of Kerala, Jharkhand, and Chhattisgarh, which got impacted in terms of five out of 10 El Nino years.

“Overall, if one analyses the precipitation by above average and below average, seven out of 10 El Nino years have resulted in lesser than average precipitation,” Srikanth said.

The exception to this trend is Odisha where eight out of 10 El Nino years have resulted in above average precipitation.

West Uttar Pradesh has had less than average rains in as many as nine.

There is also a firmly positive correlation between an El Nino during the monsoon and June-September rains in Nagaland, Manipur, Mizoram and Tripura.

“We need to look at Met subdivisions in isolation and plan accordingly in the event of El Nino happening for any particular year,” says Srikanth who blogs at ‘Chennaiyil Oru Mazhaikalam’.