Velocity and transport of the zonal current in the Luzon Strait

Some New data of CTD and ADCP, observed along PR21 Sections in the Luzon Strait, are analyzed and calculated. It is proved again that there always are zonal currents in the Luzon Strait, but the zonal currents are great varearions in the synoptic time scale. The monthly averages 0(the zonal geostrophic current velocity and transport of upper layer ocean in the Luzon Strait are calculated based on sea surface height from 1992 to 1996, which is the output of the ocean circulation model with high resolution. Those results reveal that in the Luzon Strait, the zonal currents [inflow and outflow from the South China Sea (SCS)] clear appear above 500 m; the greater current speed appears above 200 m; the average of the current speed is 50 cm/s, and the maximum current speed is above 80 cm/s, below 500 m the current speed is less than 10 cm/s. The monthly average inflow from the Pacific to the locates at the middle and the south of the strait, and its maximum current speed is about 50 cm/s and appears irt the Nov. The monthly average outflow from the SCS to the Pacific locates at the north and south of the strait, and its maximum current speed is about 50 cm/s and appears in the Nov. Too. It is related with the Bifurcation of the North Equatiorial Current, which locates at the most north (15°N) in autumn and the most south (14°N) in spring. The monthly averaga transport of the inflow and outflow are 10×10⁶ m³/s and 5×10⁶m³/s, respectively. When the predominant wind is the northeaster (from Oct. To Feb.), the inflow transport is larger than outflow, the difference between inflow and outflow is 8×10⁶ m³/s;but it is only about 3×10⁶ m³/s in other seaaons. It means that the more water outflows from other straits in south of the SCS.