This year’s monsoon could be a toss-up between aggressive negative phase of Indian Ocean Dipole (IOD) and a brewing La Nina in Equatorial Pacific, say Japanese scientists.
It’s now given that the monsoon could bump into the negative phase of IOD (warming of East of the ocean relative to West), which could hit its prospects.
While this is bad enough, what could salvage the situation is a ‘neutral’ Pacific turning expectedly monsoon-friendly La Nina.
La Nina is a phenomenon leading to cooler sea surface temperature leading to widespread rain.
Swadhin Behera of the Tokyo-based Regional Institute for Global Change told Business Line that observations were showing warm conditions in east Indian Ocean already.
“So, there is a high possibility for a strong negative IOD. The only condition that might help to negate this is a La Nina in the Pacific as it would favour a good monsoon. At this time, most models are predicting a weak La Nina or neutral condition. We will keep watching the observations and update predictions by middle of next month,” Behera said.
Akhilesh Gupta, renowned meteorological expert, says that the complex interaction between land, sea and air has not been completely understood in the context of monsoon.
NOT UNDERSTOOD
But India Meteorological Department (IMD) has chosen for the best mix possible – combine computer simulation inputs on weather/climate with statistical observations.
Influence of ocean conditions on the larger monsoon system is made known in advance – as with El Nino and La Nina in the Pacific, and the IOD.
El Nino refers to warming of East Equatorial Pacific and cooling to West Pacific (closer to Indian subcontinent). It has usually translated into a poor monsoon for India, though with no direct cause-effect relationship.
BEARS WATCHING
La Nina represents the reverse, and a warming trend closer to Indian subcontinent, which promotes storminess, cloud-building and rains over the region.
“What bears watching is whether La Nina could rollout along with monsoon,” Gupta told Business Line.
If this were to happen, one could assure oneself of a strong onset and rapid progress of monsoon during the first two months.
But beyond that, it could hold on its own. Storm systems from the Bay of Bengal and their interaction with passing western disturbances are crucial for North India.
No weather model has been able to capture how this interactive rain, a crucial decider of monsoon performance in North, would pan out, Gupta said.
Asia-Pacific Climate Centre based in Busan, South Korea, has just come out with its forecasts suggesting good rain for India in May and June but deficient in July.