Do CMIP6 models capture the observed anomalous asymmetric Hadley circulation during historical El Niño decaying stage

This study assesses the Hadley circulation (HC) anomalies’ structure during the historical El Niño decaying stage, utilizing 29 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6). While all 29 models successfully capture the climatological HC’s structure, they exhibit considerable variations in representing HC anomalies during this stage, highlighting noteworthy inter-model differences. The CMIP6 models are categorized into two distinct groups grounded on the correlation coefficient (r) between simulated anomalies of the HC and observed patterns: Type I models (r > 0.5) and Type II models (r < − 0.5). The findings elucidate that the pivotal determinant influencing the successful characterization of HC anomalies lies in the models’ capacity to simulate tropical sea surface temperature (SST) variability and the asymmetric decay rates of SST on the equatorial flanks during this stage. Type I models proficiently replicate the asymmetric structure of zonal-mean SST anomalies, which subsequently results in an asymmetric structure of HC anomalies. Conversely, Type II models generate zonal-mean SST anomalies characterized by equatorial symmetry. Therefore, these results underscore the substantial influence of El Niño–Southern Oscillation (ENSO) variability on the connection between tropical atmospheric circulation and SST. Moreover, this research offers valuable insights for improving the models' capacity to simulate tropical air–sea coupling processes effectively.