Influence of South Pacific quadrapole on austral winter precipitation over the SPCZ

Jianhuang Qin,Jianping Li,Lei Zhou,Ruiqiang Ding

doi:10.1088/1748-9326/aadd84

Abstract

The South Pacific convergence zone (SPCZ) is a key component in the weather and climate system. By analogy to the intertropical convergence zone, the SPCZ is also part of the ‘engine’ for the tropical convection. There have been many studies about the tropical impacts on the SPCZ. Here, we show that the SPCZ, especially the precipitation in this region, is subject to the influence of South Pacific quadrapole (SPQ) in the subtropics via the mechanism of wind-evaporation-sea surface temperature feedback (SST). The anomalous winds (at 850 hPa) induced by the SST anomaly gradient produce low-level convergence and activate upward motion over the SPCZ region, ultimately leading to deep convection and enhanced precipitation there. As a result, the variability in the SPQ leads the changes in the SPCZ by about 5 months. Such extratropical impacts on the SPCZ are independent of the El Niño/Southern Oscillation, which has been demonstrated to have significant impacts on the SPCZ in existing studies. The process study unveils a new connection between the subtropics in the Southern Hemisphere and the tropics, which can potentially enhance predictive understanding of the SPCZ with obvious implications for the weather and climate system.

Highlights

The South Pacific convergence zone (SPCZ), named by Trenberth (1976), displays a diagonal orientation extending from the western Pacific warm pool to the central tropical Pacific Ocean (120°W and 30°S) in the Southern Hemisphere (SH) (Vincent 1994)
The seasonal footprint mechanism suggests that an austral summertime South Pacific quadrapole (SPQ) footprint can persist until the following summer and force the atmosphere in the tropics, subsequently leading to anomalous westerlies along the equator which contributes to the onset of an El Niño–Southern Oscillation (ENSO) event
Strong positive SPQ cases are followed by positive precipitation anomalies over the SPCZ region

Summary

19 September 2018

China 4 State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, People’s Republic of China 5 Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, Chengdu University of Information Technology, Chengdu. 610225, People’s Republic of China 6 College of Global Change and Earth System Sciences (GCESS), Beijing Normal University, Beijing 100875, People’s Republic of China

Introduction

Relationship between the SPQ and precipitation over SPCZ

Findings

Conclusion and discussion