Analysis of the high-resolution observed current data in the southern area of the North Huanghai Sea in summer

The harmonic analysis method is used to analyze the high-resolution successive observed acoustic doppler current profiler (ADCP) data on a fixed station,which is located in southern area of the North Huanghai Sea.The current data is decomposed into three components:steady current which is not changing with time,periodical tidal currents and residual current,further the tidal current is decomposed to barotropictidal current and baroclinictidal current.By analyzing the components of the observed current,combining with the satellite data about the sea surface wind field,surveyed temperature profile and salinity profile data during the same period,the analysis results show that the major dynamic control fact or of the steady current in the upper layers on this station is wind stress in summer,and the characteristics of the Ekman current is quite obvious,however,the steady current direction in the middle and lOwer layers is opposite to direction in the upper layers.Basically,it shows a vertical spatial structure "flow inward in the upper layer and flow outward in the lower layer".The largest velocity of the steady current is near the surface which is larger than 5 cm/s nearly.The tidal current in each layer belongs to the regular semi-diurnal tidal currents type,the long axis direction of the major semi-diurnal tidal currents ellipse is the southeast-northwest.Basically,the maximum of tidal ellipse curvature appears near the bottom layer.In the view of the ocean current energy,the tidal current and The residual current takes large proportion on average,the ratio between the tidal current energy and the observed current energy is 77%,but the ratio of the steady current energy is only 0.6%,the baroclinic tidal current in this station is weak,and the ratio between the energies of baroclinic and barotropic tidal current components is only 5%.