Interdecadal delay of the South China Sea summer monsoon onset after 2010

Abstract

The onset of the South China Sea summer monsoon (SCSSM) implies the transition of East Asian monsoon circulation from winter to summer, which affects not only the local weather and climate near the South China Sea (SCS) but also other regions through remote teleconnection. In this paper, the interdecadal variability characteristics of the SCSSM onset is analyzed by using various datasets as well as its possible causes. The results show that there is a signi cant interdecadal change in the onset date of the SCSSM around 2010. The onset is early around May 12 during 1994-2009, conversely, the onset is signi cantly late during 1980-1993 and 2010-2020 with an average of May 29. Besides, the SCS May climate also took signi cantly decadal shift around 2010 and manifested itself in atmospheric forcing on the ocean, thus the SCSSM onset is mainly in uenced remotely by tropical Paci c SST anomaly. However, the close relationship between the SCS precipitation and tropical eastern Paci c SST drops dramatically after 1998, while its correlation with the tropical central Paci c SST rises up to -0.8 after 2010, playing a leading role. The related anomalous anticyclone over the SCS not only prevents the western Paci c subtropical high withdrawing eastward, but also weakens the activity of low-frequency oscillation and, both unfavorable for the convection formation and SCSSM onset. Therefore, besides the tropical eastern Paci c SST, more and special attentions should be paid on the tropical central Paci c SST condition, it will help us to monitor and predict the SCSSM onset effectively and improve the seasonal prediction of East Asia summer monsoon greatly.