Upwelling off East Guangdong: observation, simulation and data assimilation

We present detailed analysis of four-dimensional structures of the upwelling off East Guangdong, northern South China Sea (NSCS) in summer 2008 using in situ data, simulation and data assimilation. The data assimilation is accomplished by an Ensemble Kalman Smoother scheme applied to the Princeton Ocean Model and shows good agreement with the observations. It is shown that upwelling off East Guangdong in the NSCS initially occurred at 114.5E, east of the Pearl river estuary (PRE). The intensity of upwelling continuously increased eastward and reached its maximum near Shantou (116.7E, 23.2N). The coastline, as well as the widen shelf process, is also a factor leading to the spatial variation of the upwelling. The overlap of the plume and upwelling located alongshore from the east of the PRE to 116E indicates an interaction between them so that the strong salinity stratification of the plume water suppressed the upwelling, and simultaneously the latter inhibited the plume from extending vertically as well. When the direction of background current was in favor of upwelling, the short-term change of wind field usually only change the intensity of existing upwelling as well as the plume. The upwelling shutdown time scale was much larger than its recovering time scale after the upwelling was set up for the upwelling-favorable background current.