The observation and analysis of eastern Guangdong coastal downwelling in the winter of 2006

According to the obtained CTD data of Zhujiang River estuary and the surrounding waters during the winter cruise in 2006, it found that under the convection effect of the cooling surface water and the strong dynamical condition of northeast monsoon, wave and current act., the shelf water mixed uniform vertically, however, eastern Guangdong coastal waters has remarkable thermocline and inverse halocline, which caused by the transporting of high temperature and salinity surface water from shelf to coast under the Ekman effect of northeast monsoon, the offshore transporting of low temperature and salinity coastal bottom water under the Ekman effect of bottom boundary layer due to the southwest coastal current drived by northeast monsoon, these led to the secondary circulation in the shelf direction and downwelling in the coastal area which embodys in the phenomena of inverse halocline and thermocline in the costal area. In the area with remarkable downwelling, the dissolved oxygen concentration is uniform vertically and higher than other area. This should ascribe to downwelling effect which can bring the surface water with higher concentration dissolved oxygen to the deep layer.