Retrieving the surface axis of the Kuroshio off southern coast of Japan from SST data

One thousand and forty-nine sea surface isotherm maps during 1990~2000 were used to detect the Kuroshio axis off the coast of Japan.The current axis on the surface cannot be identified by just one indicative isotherm as is commonly done in deep water, but still there are complicated isotherms indicatives of the Kuroshio axis.Three types of isotherms indicatives of the surface axis of the Kuroshio are identified, which are nesting-warm-tongue-indicator, warm-tongue-isotherm-indicator, and isotherm-indicator.The occurrence frequency of NWTI-type is 72%, that of WTⅡ-type is 19.1% and that of Ⅱ-type is 8.9%.The vector-based and raster-based methods were introduced and used to retrieve automatically the Kuroshio paths from SST data.The total retrieving percentage is 74% by the three methods, 52.3% by the vector method, 56.8% by one raster method and 49.6% by another raster method.For the NWTI-type, the total retrieving percentage is 91.3% by the three methods, 64.4% by the vector method, 75.9% by one raster method and 65% by another raster method.Using retrieving results of the Kuroshio axis from SST data, the Kuroshio path detour is analyzed during 1990~2000.