Seasonal variation of precipitation over the Indochina Peninsula and its impact on the South China Sea spring warming

摘要

This study documents the seasonal variation of precipitation over the whole Indochina Peninsula (ICP) and associated changes in atmospheric winds and surface heat fluxes and investigates the impact of the ICP precipitation-related heating and circulation on spring sea surface warming in the South China Sea (SCS). Climatologically, most of the ICP experiences the rainy season from May to October and the period from November to April is the dry season. The summer wet-winter dry pattern dominates the seasonal rainfall variation in most regions and the maximum rainfall along the west coast occurs during June through August in association with monsoon westerly winds. A pronounced semi-annual rainfall variation is observed along central Vietnam with a primary peak in October and a secondary peak in May, which is related to northeasterly and southwesterly winds, respectively. Surface heat fluxes change drastically over the ICP in March-April and play an important role in increasing the thermal contrast with the neighbouring waters and heating the atmospheric column, which causes upward motion and precipitation over the ICP. The induced compensatory downward motion over the northern SCS leads to an increase in downward shortwave radiation and a decrease in surface wind speed and turbulent heat fluxes, which contributes to the SCS warming before the summer monsoon onset.