Decadal variation of the precipitation relationship between June and August over South China and its mechanism

Shuai Li,Zhiqiang Gong,Shaobo Qiao,Guolin Feng,Jie Yang,Shixuan Zhang

doi:10.1007/s00382-021-06073-4

Abstract

This paper investigates the causes for the interdecadal change in the relationships between early and late summer precipitation over South China (SC). It is found that the correlations of the precipitation over SC between June and August shift from weak positive in 1979–1995 to significantly negative in 1996–2019. Further analysis demonstrates that the distinct evolution of sea surface temperature (SST) pattern between the two periods accounts for the interdecadal variations of their relationships. Although the warming of the tropical western Indian Ocean (WIO) in June favors increasing precipitation over the SC via enhancing the Northwest Pacific Subtropical High (NWPSH) during the whole period, the associated SST anomalies in August are rather different between the two periods. Specifically, the WIO warming in June corresponds to slightly positive anomalies over the tropical central-eastern Pacific in August during the 1979–1995, which has weak impact on the NWPSH and results in a weak precipitation correlation between June and August. However, the WIO warming in June corresponds to La Niña’s rapid development in August during the 1996–2019, which favors the enhancement of the NWPSH via increasing the regional Hadley circulation. Due to the climatologically northward movement of NWPSH from June to August, the enhanced NWPSH in August acts to decrease the precipitation over SC, causing a significantly negative correlation between precipitation in June and August. Overall, the distinct evolution of tropical SST pattern is the key factor inducing the change of the relationships between June and August precipitation in the two periods.

Highlights

South China (SC) is in the East Asian (EA) monsoon region with significant intraseasonal and interdecadal variations of summer precipitation (Su et al.2014; Ha et al.2016; Ding et al 2008; Ha et al.2019; Wu et al 2010b )
The results from the GPCP, OAFlux and HadISST are consistent with CMA, NCEP2 and Extended Reconstructed SST (ERSST).v4, we only show the results of the latter
This paper is based on China's daily precipitation data and reanalysis data from

Summary

Introduction

South China (SC) is in the East Asian (EA) monsoon region with significant intraseasonal and interdecadal variations of summer precipitation (Su et al.2014; Ha et al.2016; Ding et al 2008; Ha et al.2019; Wu et al 2010b ). In the early 1990s and early 21st century, the summer precipitation in SC shows significant increasing and decreasing trend respectively ( Ding et al 2008; Wang et al.2009; Wu et al 2010b; Ha et al 2016, 2019), and these two interdecadal variations of summer precipitation are related to the SST anomalies in the tropical Pacific and Indian Ocean. The latent heat is decomposed in formula (5), where the first, second and third terms are affected by the difference of specific humidity in the air-sea interaction interface, the atmospheric near-surface wind anomalies and the nonlinear interaction term (small term, can be ignored), respectively. All the linear trends and climatic mean values are removed before calculation

Circulation and SST associated with reverse index

Physical mechanism of precipitation reverse change

The Physical mechanism of gradual enhancement of SST dipole

Summary and discussion