Do CMIP6 Models Capture Seasonal and Regional Differences in the Asymmetry of ENSO-Precipitation Teleconnections?

Abstract

El Niño–Southern Oscillation (ENSO) is a prominent climate phenomenon affecting precipitation patterns across much of the world. Regional ENSO-precipitation teleconnections are often asymmetric such that the precipitation response to El Niño is stronger or weaker than the response to La Niña. Better understanding of asymmetry in teleconnections can improve the predictability of climate extremes during ENSO events. In this study, we assess the capability of 50 state-of-the-art climate models and a reanalysis against observational data in simulating seasonal differences in asymmetric response of precipitation to ENSO. The analysis is performed across 46 sub-continental scale regions, using a precipitation composite technique for deriving the asymmetric component of precipitation response. Significant regional and seasonal diversity is found in the asymmetric response to ENSO, both in observations and models. Model performance in simulating the nature of teleconnections is higher than the performance in simulating the associated asymmetry. Model performance in capturing the regional diversity of asymmetry is highest in austral spring. The model biases in asymmetry are related to the inability of the models to accurately simulate the skewness of the heavy tailed local precipitation distributions and Niño3.4 SST distributions. In regions outside the Pacific and Indian Ocean basins, model bias in the skewness of local precipitation variability plays a larger role in model asymmetry bias. This analysis contributes to better understanding the fidelity of CMIP6 models in capturing asymmetry in teleconnections across different seasons and regions which are critical for making skillful projections of floods and droughts in a warming climate.