Interannual Variability of Regional Hadley Circulation and El Nino Interaction

El Nino-Southern Oscillation (ENSO) triggers variations of the global Hadley circulation (HC), while the latter may potentially feedback to ENSO events. Previous studies mainly investigated the interactions between ENSO and the global zonal-mean HC. Here, we present a regional perspective of HC variability by introducing zonal variations. Results show that El Nino intensifies the regional HC over the central-eastern Pacific, while weakening the regional HC over both the Indo-Pacific warm pool and the tropical Atlantic. The background seasonal cycle modulates the equatorial-asymmetric component of HC, with an anticlockwise (clockwise) asymmetric circulation over the central equatorial Pacific before (after) El Nino peaks. Remarkably, the asymmetric HC in boreal spring leads ENSO with a lead correlation of up to 0.68, mediated by the wind-evaporation-sea surface temperature (SST) feedback and other atmosphere-ocean dynamics. The antecedent HC anomaly may contribute to ENSO predictability.

Automated summary

El Nino triggers variations in the global Hadley circulation, while the latter may potentially feedback to El Nino events. Previous studies mainly focused on the interactions between El Nino and the zonal-mean Hadley circulation. This study introduces a regional perspective by considering zonal variations in the Hadley circulation. The results show intensification of the regional Hadley circulation over the central-eastern Pacific during El Nino, while weakening over the Indo-Pacific warm pool and the tropical Atlantic. The asymmetric component of the Hadley circulation has a lead correlation with El Nino, with the springtime anomaly leading the El Nino event.