Understanding the ENSO–East Asian winter monsoon relationship in CMIP6 models: performance evaluation and influencing factors

It is widely recognized that the East Asian winter monsoon (EAWM) has independent northern and southern modes. This study evaluated the capability of 18 Coupled Model Intercomparison Project Phase 6 models in simulating the relationship between the EAWM and El Niño–Southern Oscillation (ENSO), together with possible causes of inter-model bias. Simulations generated by 12 good-performing models demonstrate that the close relationship between the EAWM southern mode and ENSO depends on the position of the ENSO-related tripolar pattern of sea surface temperature (SST) anomalies in the tropical Indian and Pacific oceans. The positive feedback of anomalous Philippine anticyclones/cyclones with the ENSO-related east–west SST gradient over the Maritime Continent favors anomalous southerly/northerly winds in southeastern China. In contrast, the strength of the Philippine anticyclone, which is influenced by the intensity of ENSO variability, partly affects the ability of models to simulate the relationship between the EAWM northern mode and ENSO. Strong Philippine anticyclonic/cyclonic anomalies extend anomalous southerly/northerly winds from low to mid-high latitudes in East Asia. Another crucial factor in the relationship between the EAWM northern mode and ENSO is the ENSO-related Indian Ocean and South China Sea SST anomalies, which induce a poleward wave train through anomalous latent heating and subsequently generate Kuroshio anticyclonic/cyclonic anomalies.