Effect of LA NINA-EL NINO on climatic fluctuations over major Hydro Ecozones across India

Abstract

During boreal summer, the troposphere over southern hemisphere is warming at a faster rate compared to that over northern hemisphere, and the intensity of the general atmospheric as well as the Asian-Indian monsoon circulation shows decreasing trend. Over the equatorial central and eastern Pacific (Niño region), the easterlies are weakening and the SSTs rising, and there is a tendency for occurrence of frequent and intense El Niño than La Niña. Rain-producing weather systems (convergences) are frequent and intense along the western Indian subcontinent, and weaker and infrequent over Indo Gangetic plains, central India and Bay of Bengal. Consequently, monsoon rainfall is somewhat subdued over Indo-Gangetic plains and central India. The La Niña-El Niño phenomenon provides vital information for extreme rainfall activities across India. To understand effect of the phenomenon on the hydro-ecosystems of the country, difference between La Niña and El Niño years in the parameters of the hydrological wet season (HWS), summer monsoon and wet-dry spells over major/minor/sub-basins have been examined. During El Niño years, climatic condition is considerably adverse over almost the entire hydro-ecosystems across the country compared to that during La Niña years.