Strong negative CWS is found along the Chinese coast. In following month, December, negative SLC are observed in the central basin, stretching from Luzon to Vietnam, and positive SLC are found in the coastal regions in the north and in the south. The SLC lead to two cyclonic gyres of geostrophic current, one west of Luzon and the other off the southern tip of Vietnam. The negative correlation between CWS and SLC is consistent with the classic Ekman pumping scenario. Anticyclonic CWS causes higher sea level.
Monsoons are the seasonal changes of winds forced by continent-ocean temperature contrast.
A large percentage of the world's population and their agrarian economy must endure the vagaries of these monsoons. Besides bringing rain to land, monsoons also change ocean currents and upwelling. Over land the consequences of monsoon are, perhaps, well observed, but the oceanic responses have not been sufficiently monitored. The lack of observations is particularly evident in the SCS, where, until recently, conflicting territorial claims by neighboring countries have made research expedition extremely difficult. SCS is a semi-closed ocean basin whose circulation is largely driven by the seasonal change of wind.