天気図上の梅雨前線出現域の変動と前線帯への下層南風域の東西スケールについて

Eastward extension of the Baiu front in relation to zonal scale of the area with strong low-level southerly wind toward the front was examined based on the operational surface weather maps and the NCEP/NCAR re-analysis data mainly for the mature Baiu period (15 June to 31 July) from 1991 to 2000. During that period, the Baiu front on the surface weather maps appeared from the Changjiang River Basim to the east of the Japan Islands accompanied by the strong low-level southerly wind toward it in a wide zonal scala(～3500km), in many cases. However, the situations when the appesrance of the Baiu front was limited to the western part of the Japan Islands or limited to its eastern part are sometimes found with relatively narrow zonal acale of the strong low-level southerly wind toward the front, although the appearance frequency of such cases was not so high. As such the present results illustrate the importance of the zonal scale of the subtropical high for the spatial activity of the Baiu front.