The distinct impacts of the two types of ENSO on rainfall variability over Southeast Asia

This study investigates the impact of El Nino Southern Oscillation (ENSO) and ENSO Modoki on rainfall variability over Southeast Asia (SEA) with a focus on its twenty sub-regions. For the period 1979-2019, seven El Nino (EN), six La Nina (LN), five El Nino Modoki (EM), and five La Nina Modoki (LM) events were identified. In the boreal summer (JJA) and winter (DJF) of EN events, rainfall reduction occurred over the Maritime Continent and the Philippines except for West Philippines in JJA and West Kalimantan in DJF. Similar patterns but with enhanced drier/wetter conditions were detected during EM. During LN, rainfall increased in most sub-regions except for West Philippines and parts of mainland Indochina in JJA, and in DJF in some southern areas such as South Sumatra, West Kalimantan, and Papua. Compared to LN, LM generally exhibited less wet/drier conditions in JJA over most sub-regions and wetter conditions in DJF over a major part of the Maritime Continent. The decrease (increase) in rainfall over SEA during Modoki events compared to the canonical ENSO events was explained by a reduced (enhanced) moisture transport into the region and a weakening (strengthening) of the ascending branch of the Walker circulation.