Relationship between tropospheric circulation over the western North Pacific and tropical cyclone approach/landfall on Japan

The relationship between large-scale seasonal (June-October) circulation over the western North Pacific, and the frequency of tropical cyclone (TC) approach or landfall on Japan, is examined using the reanalysis datasets (ERA-40(1958-2001) and JRA-25(1979-2004)). The result shows that there are two dominant modes over the western North Pacific; the El Nino Southern Oscillation (ENSO) mode, and a mode that is correlated with the variation of the subtropical high. In years when the subtropical high extends westward from its climatological position and the maximum of the high pressure anomaly is located along the Tropic of Cancer, the frequency of TC approach/landfall on Japan tends to be reduced. In contrary, when the subtropical high retreats eastward, and the maximum of low pressure anomaly is located along the Tropic of Cancer, there is a tendency to have more number of tropical cyclones approach or landfall on Japan.