The cloud‐radiative effect when simulating strength asymmetry in two types of El Niño events using CMIP5 models

It has been suggested that the strength asymmetry of the Bjerknes feedback is responsible for the pronounced amplitude asymmetry between eastern Pacific (EP) and central Pacific (CP) El Niño events. Detailed analyses have indicated that this strength asymmetry is mainly derived from the weaker sensitivity of the zonal sea level pressure (SLP) anomaly to that of the diabatic heating anomaly during the development phase of CP El Niño events, which mainly results from the large cancelation induced by the negative sea surface temperature (SST)‐cloud thermodynamic feedback that negates the positive dynamical feedback. This study validates these conclusions by using historical runs of 20 models involved in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our results suggest that the CMIP5 models generally depict the asymmetry in amplitude between the two types of El Niño events well, which is consistent with successfully simulating the strength asymmetry of the Bjerknes feedback. As observed during both types of El Niño events, variations in the total cloud amount and shortwave radiation also indicated that the cloud‐radiative effect is an important factor that causes amplitude asymmetry between CP and EP El Niño events. However, the CMIP5 models are severely biased when capturing realistic CP El Niño structures, namely few models can simulate the significantly weaker warming anomalies in the EP relative to the CP.