Rainfall Variability during El Nino, La Nina and Neutral Years Over Karnataka

Abstract

The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. The three phases of the El Niño–Southern Oscillation (ENSO) namely the neutral phase, El Niño and La Niña oscillations. El Niño refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific. The state of Karnataka is located on a table land in the angle where the Western and Eastern Ghat ranges converge into the Nilgiri hill complex. 41 year (1980-2020) average annual rainfall of Karnataka collected from the rain gauge station located under the farm universities of Karnataka and, SST and SOI data collected from NOAA were used to study the rainfall variability while ENSO events. The El Niño events will deviate the rainy winds towards eastern pacific region causing lesser rainfall on Indian sub-continent or draughts in some years, but when it comes to Karnataka El Niño events have given above average rainfall. There were 8 episodes of excess rainfall and 6 episodes of deficient rainfall during the 14 El Niño episodes, and 3 episodes of excess rainfall and 8 episodes of deficient rainfall during the 11 La Niña episodes. The remaining 16 episodes were neutral years, with 10 episodes having excessive rainfall and the remaining 6 having deficient rainfall. Hence the El Niño episodes is good when compared to La Niña episodes over Karnataka.