Seasonal Variability Of Current System In The Kuroshio South Of Japan And Kuroshio Extension

Based on the U.S. Navy Generalized Digital Environmental Model (GDEM) climatological temperature and salinity data on a 0.5 X 0.5 grid, the three-dimensional current system in the Kuroshio south of Japan and Kuroshio Extension is determined and analyzed by using the P-vector method. The Kuroshio meander is well identified in the sea area(25 N~40 N, 134 E-178 E). The result presents the characteristics of the current system, including current path, width, velocity, volume transport, display seasonal variation evidently.In this paper, the P-vector method which is based on -spiral method andthermal wind relation is used and a good result is obtained, which indicates the P-vector method can be used in the large-scale ocean area and invert the current system well.The Kuroshio meander south of Japan and the two lee-wave meanders in the Kuroshio Extension are well presented by the P-vector method. The path of the Kuroshio meander, the position of the meanders in the Kuroshio Extension, the bifurcation of the Kuroshio Extension and the width of the current display seasonal variation evidently.South of Japan, the Kuroshio path of maximal velocity is outside the other three seasons in winter. In the Kuroshio Extension, the two points of the lee-wave also shows seasonal variabilities, and the path is most winding in summer, straight in fall.The surface current velocity displays the seasonal variability, too. The velocity varies from 71.6cm/s (maximum) in December to 55.4cm/s (minimum) in May in the Kuroshio south of Japan, and the position 01 extreme appear to the south of Kii Peninsula. The velocity varies from 61.5cm/s (maximum) in June to 48.1cm/s (minimum) in March in the Kuroshio Extension, and the extreme appear at the position of the first meander. The extreme minish, and the month and position of theextreme change accordingly as it deepens.In this paper, four meridional sections which are 136?E, 140?E, 152?E and 170 E have been chosen to study the seasonal variability of the volume transport and velocity. The result shows the volume transport in the four sections have the maximum in summer and the minimum in winter, especially in the two sections of 140 Band 170 E.The eddy structure in both sides of the Kuroshio Extension is another distinct character. The eddies are strongest in summer and weakest in spring as a whole. There are two evident cyclonic eddies whose centers lie at 34 N,164 Band 33 N,176 E, and two evident anti-cyclonic eddies whose centers lie at 33 N,175 E and 32 N, 162.5 E. The result seems to suggest a causal relation between the formation, evolution and disappearance of the eddy and the Kuroshio meander path.From the pictures of the three-dimensional current system, we can see that the magnitude of the Kuroshio current minishes as it deepens. The current field in 200m displays the same seasonal variation as the surface, but at the 500m even 1000m depth, we cannot identify them at all.