The South China Sea summer monsoon (SCSSM) is a major member in the East Asian summer monsoon.Its onset marks the fully establishment of the summertime circulation over East Asia. Previous studies have treated ENSO events as one of the major influence factors for the evident interannual variation of SCSSM onset time.
Supported by the Institute of Atmospheric Physics LASG open research program, Dr. LIU Boqi, ZHU Congwen (Chinese Academy of Meteorological Sciences) and their collaborators have investigated SCSSM onset time and suggest that the interannual variation of SCSSM onset is quite different before and after 1993/94. Their results show that the sea surface temperature anomalies (SSTAs) over the southern Indian Ocean in boreal spring could modulate the SCSSM onset time by changing the low-level circulation surrounding the SCS in 1980-1993 period. While the ENSO event and its resultant SSTAs over the tropical Indian Ocean determines the abnormal upper-level circulation near the SCS, leading to the interannual variation of SCSSM onset time in 1994-2014 period.
Figure (a) Onset time of SCSSM (pentad, red bars: El Nino in previous winter, blue bars: La Nina in previous winter); (b, c) 10-20N averaged pressure-longitudinal cross section of the diabatic heating (contours, K day-1) and zonal circulation (vectors, m s-1) regressed against SCSSM onset time in 1980-1993 and 1994-2014, respectively; (d, e) SSTAs associated with interannual variation of the SCSSM onset time (K) in 1980-1993 and 1994-2014, respectively. (Liu et al, 2016)
The definition of SCSSM onset time in this work has been applied by the National Climate Center in its real-time monitoring system (http://cmdp.ncc-cma.net/Monitoring/monsoon_mtg.php).
Reference:
Liu, BQ, CW Zhu, Y Yuan, K Xu, 2016: Two Types of Interannual Variability of South China Sea Summer Monsoon Onset Related to the SST Anomalies before and after 1993/94. J. Climate, 29, 6957–6971.
Download: http://journals.ametsoc.org/doi/full/10.1175/JCLI-D-16-0065.1
Contact: LIU Boqi, lbq@lasg.iap.ac.cn
