SPATIAL DISTRIBUTION OF HOUR-SPECIFIC WIND DIRECTION VARIATION IN JAPAN

Abstract

This study presents a statistical analysis of the spatial distribution of the hourly variations in the wind-direction angle in Japan (including the offshore areas) using the local objective analysis data. The spatial distribution of the year-round average indicated that the variations over the land areas were larger than those over the surrounding sea areas; notably, the variations over offshore areas were smaller farther away from the coastline. In winter (January), the variations in the wind-direction angle were large near the Japan-sea Polar airmass Convergence Zone (JPCZ) and the local discontinuity line. In summer (July), the variations in the wind-direction angle in the Pacific Ocean were smaller than those in the Japan Sea. In the coastal areas, the variations increased temporarily during certain periods; this could be attributed to the periods of transition between the land and sea breezes. The results suggested that the variations in the wind direction were seasonal and diurnal and were primarily affected by the regional climatic conditions.