Response of the cold water mass in the western South China Sea to the wind stress curl associated with the summer monsoon

Analys is of clmiatological observation temperature data reveals that during the southw esterly monsoon, there exists a low tem perature zone east of Vietnam.It cools down from June to August and warms up in September.Mean while, during this period, the cold watermass spreads easwtard to the deep bas in.Num erical experiments validate the results of data analysis and further verify that there are two basic factors that induce the Vietnam cold water.The major one is the strong local positive wind stress curl, which leads to the divergence of sea surface water and the upward supplement of lower layer water in the deep basin.Anotherminor one is the alongshore component of south westerly monsoon, which drives the offshore Ekman transport and coastal upwelling in the shallowregion along the Vietnam coast. In add ition, the negative wind stress curl in the southern South China Sea inputs negative vorticity to the ocean and drives a strong anticyclonic gyre, which affects the spatial distribution of the cold water evidently.