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

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 are analyzed by using various datasets as well as its possible mechanisms. The results show that there is a significant interdecadal delay in the onset date of the SCSSM after 2010. The onset is early around May 13th during 1994–2009. However, the onset is significantly later during 2010–2020 with an average of May 30th. Besides, the air and ocean conditions in SCS in May also took a significant decadal shift around 2010 and manifested itself in atmospheric forcing on the ocean, thus the SCSSM onset is mainly remotely influenced by the tropical Ocean instead of local SST. It is found that the interdecadal variation of the SCSSM onset is mainly caused by the decadal warming/cooling of the tropical central Pacific SST. The SCSSM onset's relationship with the tropical central Pacific SST seems more binding and stable relative to that with the tropical eastern Pacific SST. Their correlation is stable and still reaches the significant test in recent years. Therefore, the warming of the tropical central Pacific SST during 2010–2020 tends to postpone the SCSSM onset by means of related anomalous anticyclones and weakened activity of low-frequency Oscillation and tropical cyclones. On the contrary, its cooling led to early SCSSM onset during 1994–2009. Therefore, more and special attention should be paid to the tropical central Pacific SST anomaly, it will help us to monitor and predict the SCSSM onset effectively, and improve the seasonal prediction of East Asia summer monsoon greatly. [ABSTRACT FROM AUTHOR]