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Warm Indian Ocean poses threat to monsoon, says Japanese scientist

Vinson Kurian Thiruvananthapuram | Updated on November 25, 2017 Published on July 01, 2014

Extended pre-monsoon showers too could have impacted the monsoon play-out. Photo:   -  Thulasi Kakkat

The El Nino is not the only factor that tripped monsoon rains in India during June, according to a lead scientist with a research group Japanese national forecaster Jamstec.

This is the latest in a series of expert voices which has shared the view that local factors have played no small a role in short-circuiting monsoon during the first month of the season.

RARE COMBINATION

“The El Nino is still evolving and perhaps it is not the only factor that caused the deficit rainfall in June,” says Swadhin Behera, Group Leader in the Application Research Laboratory for the Climate Variability Prediction and Application under Jamstec.

“I believe the combined effect of the warm eastern Indian Ocean (near Sumatra) and the evolving El Nino is responsible for the deficit this time,” Behera wrote to Business Line in an e-mail.

The warm tropical eastern Indian Ocean is usually inversely related with monsoon rainfall and the El Nino adds on to that.

The monsoon is affected strongly because of a co-occurrence of warm eastern Indian Ocean with El Nino. “This is a rare combination but when it happens, it is quite lethal for the summer monsoon,” Behera said.

CLOSEST PARALLEL

The closest parallel one sees is the condition in June 1992. But each event is different, he observed.

“But the progress of the El Nino; a warm eastern Indian Ocean morphing into a negative Indian Ocean Dipole effect; and the monsoon this year, might not be the same as what we saw in 1992.”

Negative Indian Ocean Dipole (IOD) results from the anomalous warming of East Indian Ocean relative to the west and has been found to be harmful for a concurrent Indian monsoon.

Answering a specific question, Behera said that the El Nino was expected to peak in September/October, earlier than usual.

SUBDUED MONSOON

“We also expect it to be a moderate event unlike the strong events of 1997 and 2006. However, if the present warming of the eastern Indian Ocean continues, the monsoon will remain subdued.”

Behera agreed that extended pre-monsoon showers too could have impacted the monsoon play-out.

But he observed that the land-sea temperature gradient is also affected by the warmer seas on both sides of the sub-continent.

“The Arabian Sea is quite warm at this time (relative to the Bay of Bengal). Even this could be another adverse factor.”

Published on July 01, 2014
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