Nowcasting/forecasting system of the ocean circulation off Rokkasho village

In, Teiji*; Nakayama, Tomoharu*; Matsuura, Yasutaka*; Shima, Shigeki*; Ishikawa, Yoichi*; Awaji, Toshiyuki*; Kobayashi, Takuya ; Kawamura, Hideyuki  ; Togawa, Orihiko 

We have been developing an oceanic forecasting/nowcasting system for the coastal area near Rokkasho village, which locates in the northern part of Honshu Island of Japan. Associated with the geographic features, the oceanographic condition in this area is very complicated. Previous observations show that the seasonal variation in this region is characterized by the two different modes: the coastal mode in a cold season in which flow takes a straight path along the Japan coast, and the gyre mode in a warm season in which swirl-like circulation appears. When attempting the accurate nowcast/forecast of this complicated regional circulation, a downscaling method is an effective approach since it enables us to use such a high resolution 4-dimensional variational data assimilation system. In fact, our forecast result using the high resolution data assimilation system demonstrates the good performance of reproducing both modes in a hindcast sense.