Effect of El Ni\xf1o on the response ratio of Hadley circulation to different SST meridional structures

Juan Feng,Fei-Fei Jin,Sen Zhao,Zhengyu Liu,Jianping Li

doi:10.1007/s00382-019-04756-7

Abstract

The role of El Niño in influencing the response of the Hadley circulation (HC) to different tropical sea surface temperature (SST) meridional structures is investigated over the period 1979–2016. The explained variance of the equatorially asymmetric principal mode of HC variability is enhanced during El Niño events that are characterized by equatorially symmetric El Niño SST anomalies. It is shown that the response of the HC to different SST meridional structures is greatly enhanced in El Niño events; this is because the SST over the Indo-Pacific warm pool (IPWP) shows inhomogeneous warming in El Niño events, with greater values in the southern IPWP. The asymmetric warming over the IPWP is opposite to the climatological meridional structure of the SST over the IPWP, which intensifies the equatorially symmetric variation of SST, and contributes to the enhanced response of the HC to SST. This point is further verified by the suppression of this enhanced response in El Niño events of the HC to SST when the effects of SST over the IPWP are removed, implying that the different warming amplitude within the IPWP during the El Niño events contributes to the enhanced response. The response in La Niña events is also explored, indicating a difference between El Niño and La Niña events. These results may help explain the corresponding variations of the HC during the El Niño events, and highlight the different influences of the El Niño and La Niña events on the response of the HC to SST.

Highlights

El Niño is associated with equatorially symmetric sea surface temperature (SST) anomalies, which are connected with equatorially symmetric meridional circulation (Lindzen and Nigam 1987; Feng and Li 2013)
We found that the principal mode of the Hadley circulation (HC) variability, is strengthened rather than suppressed, with greater explained variance during the El Niño events
By examining the regional SST characteristics during the El Niño events, we found that the anomalous SST over the tropical Pacific and Atlantic are both equatorially symmetric during the El Niño events, but the SST over the Indo-Pacific warm pool (IPWP) is not

Summary

Introduction

The El Niño/Southern Oscillation (ENSO) phenomenon is the most significant interannual climate signal in the tropical atmosphere–ocean interaction, and has widespread impacts on the global climate system and socio-economic activity. There has been extensive research into its dynamics (e.g., Bjerknes 1969; Cane and Zebiak 1985; Picaut et al 1997), interannual variations (e.g., Jin 1997a, b; Wang et al 1999; Latif and Keenlysid 2008), decadal variability (e.g., Latif et al 1997; Zhang et al 1997), and regional impacts (e.g., Nicholls 1979; Kiladis and Diaz 1989; Tomita and Yasunari 1996; Wang et al 2000; Xie et al 2009; Feng and Li 2011).

Objectives

Methods

Findings

Conclusion