1250 / 2024-09-20 20:07:16

Uncertainties of ENSO-related Regional Hadley Circulation Anomalies within CMIP6 Models

regional Hadley circulation,ENSO,cold tongue bias,CMIP6,asymmetric component

Hadley circulation (HC) is a fundamental component of global atmospheric circulation and plays an important role in global energy and water vapor transport. The interactions between ENSO and HC significantly impact tropical climatic systems. Previous studies on ENSO-related HC have been performed more in a global perspective, but ENSO-related HC has a strong regionality. Meanwhile, model simulation results are usually used to investigate HC, which motivates us to systematically assess the ability of state-of-the-art models to reproduce the spatial characteristics and intensity of ENSO-related HC in a regional perspective. In this study, we assess the ENSO-related HC among 55 CMIP6 models using an ensemble mean of eight reanalyses as a proxy for observations. The results show that the ENSO-related HC of the ensemble mean of CMIP6 models is westward shifted over the central-eastern Pacific and underestimated over most areas compared to the ensemble mean of reanalyses. We further find that the westward extension of the cold tongue causes the westward shift of ENSO-related HC over the central-eastern Pacific in the CMIP6 models compared to reanalyses, and the southward shift of ENSO-related SST over the Central-Western Pacific ITCZ causes a weakening of the asymmetric component of ENSO-related HC over the equatorial Pacific in the CMIP6 models compared to reanalyses. Additionally, the extent of the westward shift, southward shift, and weakening varies among the models, contributing collectively to the biases.