Attainment of a Geostrophic Flow Balance in the Upper Layer of the Kuroshio South of Japan

摘要

As the observed ADCP velocity in the upper layer has been used as the reference velocity of the geostrophic flow estimation, the attainment of a geostrophic flow balance of the ADCP velocity is needed in the upper layer. Focussing upon this point of view, the attainment of the geostrophic flow balance of the Kuroshio is checked by use of six observational line data fromjuly 1992 to August 2001 obtained by the training vessel "Seisui-Maru" of Mie University. The attainment of a geostrophic flow balance can be examined by the comparison of the vertical difference in the ADCP velocity (ADCP D.) with that of the calculated geostrophic flow velocity (GST. D.), which does not depend on the reference level. It is shown that the attainment of a geostrophic flow balance is unclear in the upper layer of the Kuroshio, which implies that the regression line of the ADCP D. and GST. D. should be carefully checked, if the ADCP velocity in the upper layer is used as the reference velocity. The formation process of a non-geostrophic flow balance is also discussed.