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Abstract:
El Niño - Southern Oscillation (ENSO) has an important impact on the strength and location of the Hadley circulation (HC), while the latter may have reactions to the ENSO. Previous studies have mainly focused on the global perspective. However, recent studies have shown that the structure of the HC is not uniform in different regions, and that the interaction of the HC and jets tend to stimulate stationary Rossby waves that propagate to higher latitudes and affect the climate in the polar regions. Here, we construct the three-dimensional structure of the HC and investigate its equatorial symmetric and asymmetric components associated with ENSO as well as the impact on polar climate. Results show that El Niño events strengthen the HC over the central-eastern Pacific but weaken the HC over the Indo-western Pacific and tropical Atlantic. With the seasonal evolution of the El Niño event, the central equatorial Pacific is dominated by an equatorial asymmetric anticlockwise (clockwise) circulation before (after) the peak of El Niño. This process is closely related to the wind-evaporation-SST feedback, the Bjerknes feedback, and other atmosphere-ocean interactions. More importantly, during the spring of the developing year, the asymmetric anticlockwise circulation over the central Pacific has a strong lead correlation with ENSO, which may contribute to the prediction of ENSO. The interaction of HC and ENSO further influences the polar climate through atmospheric teleconnection patterns.
