Item

Abstract

The East Asian winter monsoon (EAWM) exerts impacts on climate in the regions from East Asia down to the Maritime Continent. The El Niño-Southern Oscillation (ENSO) affects not only the tropical climate, but also the extratropical climate. This study evaluates the relationship between El Niño-Southern Oscillation (ENSO) and the East Asian winter monsoon (EAWM) in 26 Coupled Model Intercomparison Project phase 6 (CMIP6) models. Results show that the model’s ability of simulating the ENSO-EAWM relationship is more dependent upon the longitudinal extension of ENSO-related equatorial Pacific sea surface temperature (SST) anomalies than the amplitude of the equatorial central-eastern Pacific SST anomalies. The influence of the amplitude of ENSO on the simulation of the ENSO-EAWM relationship depends on the westward extension of ENSO-related equatorial Pacific SST anomalies. Another factor for the model’s ability of simulating the ENSO-EAWM relationship is the SST anomalies in the tropical western North Pacific (WNP). A westward extension of the equatorial Pacific SST anomalies shifts the west branch of anomalous Walker circulation too far westward, which causes westward displaced anomalous ascending (descending) motion around the Philippine Sea through modulating regional meridional vertical circulation in El Niño (La Niña) years. The weak SST anomalies in the tropical WNP lead to the failure of inducing anomalous lower-level anticyclone (cyclone) over the Philippine Sea through a Rossby wave response in El Niño (La Niña) years. The accompanying weak anomalous lower-level southwesterly (northeasterly) winds along the west flank of the anomalous anticyclone (cyclone) account for the weak ENSO-EAWM relationship.