Enhanced Impacts of ENSO on the Southeast Asian Summer Monsoon Under Global Warming and Associated Mechanisms

Abstract

Based on outputs of 28 coupled models from the Phase 6 of the Coupled Model Intercomparison Project (CMIP6), we show that the response of the Southeast Asian summer monsoon to the El Niño-Southern Oscillation (ENSO) during post-ENSO summer will likely strengthen in a warmer climate, which can be attributed to concurrently weakened sea-surface temperature anomalies (SSTAs) in the western equatorial Pacific (WEP). The weakened WEP SSTAs are primarily caused by enhanced latent heat damping due to increased surface wind speed anomalies, which are associated with the eastward shift of the El Niño-induced anomalous Walker circulation due to El Niño-like sea surface temperature change in the tropical Pacific under global warming. Besides, the climatological zonal ocean currents will slow down due to the weakening of climatological Walker circulation, which also acts to weaken the WEP SSTAs via reducing the advection of anomalous temperature by the mean current.