Distinct impacts of pure El Niño events on spring rainfall of Sri Lanka

Abstract The El Niño Southern Oscillation (ENSO) strongly influences the climate of the tropical Indo-Pacific region, but the specific impact of pure El Niño events on Sri Lanka's rainfall remains largely unexplored. By analyzing observational and reanalysis datasets from 1981 to 2023, we investigate this relationship, particularly during the El Niño decaying spring season. Our results show that during pure Central Pacific (CP) El Niño events, Sri Lanka experiences enhanced spring rainfall due to warmer sea surface temperatures (SST) in the tropical Indian Ocean and strong westerly winds over the Arabian Sea, which favor moisture convergence and subsequent rainfall enhancement over Sri Lanka. Conversely, during pure Eastern Pacific (EP) El Niño events, spring rainfall is reduced due to cooler SST and stronger easterly winds inducing anti-cyclonic circulation over the Arabian Sea, resulting in moisture divergence and reduced rainfall. These contrasting responses highlight the distinct impacts of pure El Niño events on the rainfall of Sri Lanka and associated ocean-atmosphere dynamics, providing valuable insights for future climate projections and adaptation strategies in the country.