Interdecadal Variations in Extreme High–Temperature Events over Southern China in the Early 2000s and the Influence of the Pacific Decadal Oscillation

Baoyan Zhu,Huijun Wang,Bo Sun,Hua Li

doi:10.3390/atmos11080829

Abstract

This study documents a sudden interdecadal variation in the frequency of extreme high–temperature events (FEHE) over southern China during summer in the early 2000s, which is characterized by a relatively small (large) FEHE during 1991–2000 (2003–2018). The composite analysis on the extreme high–temperature events (EHEs) over southern China indicates that the occurrence of EHEs is mainly influenced by increased downward surface net shortwave radiation, which is induced by the cloud–forced radiation anomalies associated with reduced cloud; the reduced cloud is attributed to anomalous descent motion and decreased water vapor content in the troposphere. Compared to the situation during 1991–2000, anomalous descent motion and decreased atmospheric water vapor content occurred over southern China in summer during 2003–2018, providing a more favorable climatic condition for EHEs. This interdecadal variation is associated with the strengthened Pacific Walker circulation after 2003. The Pacific decadal oscillation (PDO) is suggested to be an important driver for the above interdecadal variation, which shifted from a positive phase towards a negative phase after 2003. Numerical experiments demonstrate that a negative phase of PDO may induce a strengthened Walker circulation and anomalous atmospheric descent motion as well as water vapor divergence over Southern China.

Highlights

Under the background of climate change, extreme high–temperature events (EHEs) increasingly occur and exert a great influence on human health, agriculture and social activities on a global scale, which attracts increasing studies focusing on EHEs [1,2,3,4,5]
The frequency of EHEs (FEHE) in southern China underwent an interdecadal variation in the early 2000s, characterized by a relatively small FEHE during 1991–2000 and a relatively large FEHE during 2003–2018
At the synoptic time scale, the occurrence of extreme high–temperature events (EHEs) over southern China is mainly influenced by increased downward surface net shortwave radiation, which is induced by the cloud–forced radiation anomalies associated with reduced cloud

Summary

Introduction

Under the background of climate change, extreme high–temperature events (EHEs) increasingly occur and exert a great influence on human health, agriculture and social activities on a global scale, which attracts increasing studies focusing on EHEs [1,2,3,4,5]. Europe underwent two devastating EHEs in 2003 and 2010, which led to about 70,000 and 55,000 heat–related deaths, respectively [1,6]. The frequency of EHEs (FEHE) underwent a significant increasing trend over all of eastern China (105◦ E east), except for a weak decreasing trend that was observed over the Yangtze. River Valley [10,11,12] Anthropogenic factors such as greenhouse gas emissions and urbanization play

Methods

Discussion

Conclusion