PANAJI: While climate change is producing catastrophically heavier rainfall in fewer hours, scientists at the National Institute of Oceanography (NIO) have found that break spells in India during unfavourable El Nino conditions are longer and more frequent than in La Nina years.
In a phenomenon called El Nino, warming of sea surface temperatures in eastern equatorial Pacific, near the Peru coast — or the cooling effect in the same region called La Nina — affects the Indian southwest
monsoon negatively or positively.
The study by Shivananda Pai, Lata Sridhar and M R Ramesh Kumar on ‘Active and break events of Indian summer monsoon during 1901-2014’ was published in Climate Dynamics some years ago. Recently, it has been updated till 2020. The scientists have crunched figures to stretch the study related to peak season conditions and dry spells every July and August to 120 years.
In all, there were 28 El Nino years and 24 La Nina years during the last 120 years. “The active and break spells of various durations during these years (both phenomena) show similar distribution with spells of short durations being more frequent than those of long durations. However, break spells of long duration are more frequent during El Nino years than the La Nina years,” the study states.
During El Nino years, there were 297 break days as against 172 during La Nina years, 193 active days, as compared to 183 during La Nina. “This works out to an average of 10.6 El Nino break days and 7.17 La Nina break days and 6.9 El Nino and 7.63 La Nina active days per season respectively,” Kumar, a meteorologist stated.
The recent wet spell in Goa has yielded more than 700mm — about 70% of the July rainfall — in less than ten days, after a weak monsoon produced 350mm in 20 days. In Germany, it was reported that, in a rare episode, rainfall that would occur in two months fell in just a few hours, as rivers burst their banks in many places.
In an earlier study, Kumar meteorologist had found that analysis of daily rainfall data over India during 1951-2007 revealed “an increased propensity in the occurrence of monsoon-breaks of more than one week over the subcontinent”.
“The increasing trend is seen both in the duration and frequency of monsoon-breaks over the subcontinent,” his paper stated.