Southward-shift zonal wind patterns during ENSO in CMIP6 models

To what extent the CMIP6 models are capable of simulating the location and amplitude of zonal wind anomalies in tropical Pacific during the mature phase of ENSO is examined. While most of the models capture the southward shift of the maximum zonal wind anomaly, the simulated locations are less southward and more westward and the simulated intensities are weaker compared to the observation. An anti-symmetric momentum budget analysis reveals that the southward shift in the models results from the anomalous meridional advection, consistent with that derived from the observation. An inter-model regression analysis reveals that the longitudinal and latitudinal locations of the model zonal wind response depend on the mean precipitation pattern in the tropical western Pacific (WP). A stronger southward (eastward) mean precipitation gradient leads to a more southward (eastward) location. In addition, the simulated zonal wind intensity is determined by both area-averaged mean precipitation over WP and anomalous SST intensity in the equatorial eastern Pacific. Therefore, an improved mean precipitation simulation in WP may help reproduce realistic atmospheric responses to ENSO.