Characteristics of Convection Activities over Asian-Australian “Land Bridge” Area and Its Relationship with SCS Summer Monsoon Onset

摘要

Based on 1980-1997 TBB data from GMS of Japan, NCEP/NCAR reanalysis data (1958-1997) and 1980-1997 precipitation data from CMAP, an investigation is carried out of characteristics of convection activities over Asian-Australian “Land Bridge” area and its relationship with SCS summer monsoon (SCSSM) onset. The results show that the onset of SCSSM bears a close relation to the systematic moving of the convection center over Sumatra along “land bridge” from winter to summer. It is a foreboding that the convection shifts most rapidly, which affects directly the subsequent enhancement of Indo-China Peninsula convection (ICPC) followed by the rupture of the subtropical high (SH) band in this region leading to SCSSM establishment. The further study suggests that the intensity of Sumatra convection (SC) has a close relation to the SSTA and zonal vertical circulations: when the central-eastern equatorial Pacific SST is warmer (colder), the walker circulation is weaker (stronger), Sumatra convection is weaker (stronger), the equatorial westerly is weaker (stronger) which will be associated with the following ICPC and SCSSM. The effect of ICPC on the SH belt splitting, as well as the Bay of Bengal (BOB) convection, has been researched by numerical modeling, and the results of simulation indicate that the SCSSM onset is due to a Rossby-wave triggered by convection around BOB.