The Influence of Internal Tide on the Diagnostic Calculation of Geostrophic Current in Luzon Strait

On the basis of CTD data obtained on 4 repeat-observed stations located at 121°E,19.5°N ~21°N in the Luzon Strait of the cruise in the summer of 2008,the role of disturbances caused by internal tides in temperature and salinity profiles in calculating of the geostrophic currents is discussed.The result shows that the role of disturbances caused by internal tides in temperature and salinity profiles in calculating of the geostrophic currents is significant.When we use hydrographic data to calculate the geostrophic currents we have to take measures to remove the disturbances caused by internal tides in temperature and salinity profiles,unless there would be great errors.By using the time-averaged CTD data,the geostrophic currents in the Luzon Strait is calculated.The result reveals that the significant part of the geostrophic currents appear above 350 m.Kuroshio intrusion mainly happens between 19.5°N and 21°N,especially at the upper layer.Between 19.5°N and 21°N,the water volume transport shows a in at upper and flowing out at deeper layer vertical structure,above 350 m the transport is westward(2.6 Sv) and below 350 m it is eastward(3.1 Sv).The distribution of the geostrophic currents we get is confirmed by the salinity distribution along 121°E Section.