Asymmetric Impacts of El Nino Development and Decay Stages on the Hadley Circulation

The impact of El Nino on the Hadley Circulation (HC) has been a topic of previous studies, but the results have been inconclusive. We study how El Nino affects the HC during different stages of its cycle. In development years, the HC anomaly shows an equatorial quasi-symmetric pattern, while in decay years, it shows an asymmetric pattern. This resolves previous discrepancies among studies about El Nino's impacts on the HC. The differences in tropical sea surface temperature (SST) during different stages of El Nino cause differences in SST meridional gradients, which determine the location of convergence. This explains why the HC anomalies have different spatial structures during El Nino development and decay years. Our results show that the meridional distribution of SST during different El Nino stages has significantly distinct impacts on meridional circulation and clarify the differences in El Nino's effects on climate.

Automated summary

The impact of El Nino on the Hadley Circulation (HC) has been a topic of previous studies, but the results have been inconclusive. This study investigates how El Nino affects the HC during different stages of its cycle, resolving previous discrepancies among studies. The differences in tropical sea surface temperature (SST) during different stages of El Nino cause differences in SST meridional gradients, which determine the location of convergence and thus explain the different spatial structures of HC anomalies during El Nino development and decay years.