台風発生期の流れの場についての解析

Abstract

The characteristics of the upper (200 mb) and lower (850 mb) tropospheric wind fields duringtyphoon season, between July and October in 1980, were analyzed. There were 16 tropicalstorms formed during this period over the northern part of the Western Pasific. GMS satellitewind data and sonde wind data are used to make the grid point wind fields. To analyze the low-er wind fields, MASCON model is used to adjust the interpolated wind fields.In latitudes of 5N-15N at lower level westerly wind in the western part is usually boundedon the east by easterly wind. Many of analyzed tropical storms became tropical depressions nearthis boundery area. In the divergence and relative vorticity fields, the disturbances which havepositive vorticity and convergence at 850 mb-level, and negative vorticity and divergence at 200mb level can be traced from the area around 170 E about 2-3 days before the formations of tro-pical depressions. The disturbances propagate west-northwestward and their paths are not de-pendent on that they later develop into typhoons or not.