Numerical Simulations of Impacts of Land Surface and Sea Surface Temperatures on the Onset Date of South China Sea Summer Monsoon

The present study analyzes differences in spatial and temporal variations of surface temperature between early and late onset years of the South China Sea summer monsoon (SCSSM). It is found that when land surface temperature north of 40degN is lower (higher) and the sea surface temperature over the South China Sea-western North Pacific(SCS-WNP) is higher (lower) in winter, the onset of the SCSSM begins earlier (later) and that when land surface temperature north of 40degN is higher (lower) and sea surface temperature over the SCS-WNP is lower (higher) in spring, the onset of the SCSSM occurs earlier (later). In order to verify the mechanism of influences of the land and sea surface temperature distribution patterns and test the ability of the p-sigma regional climate model (P-sigmaRCM9) to simulate the SCSSM onset, three types of years with early, normal and late SCSSM onset are selected and the SCSSM regimes are numerically simulated. According to the results obtained from five sensitive experiments, it is revealed that when the land surface temperature is higher in the eastern part north of 40degN and lower in the western part north of 40degN, and it rises faster in eastern coastal regions and Indian Peninsula, while sea surface temperature over the SCS-WNP is lower, the early onset of the SCSSM can be expected.