A Study on Climatological Aspects of Winds in Japan. Part II: Mean Fields of the Thermal Wind

Climatelogical aspects of the geostrophic wind calculated from geopotential heights in the planetary boundary layer in Japan have been investigated. The mean geostrophic winds at the 850 mb level nearly agree with the observed 850 mb winds in both magnitude and direction, with some exceptions. The mean geostrophic wind vectors at the 850 mb and 1000 mb levels for each site are significantly different from each other, especially in winter. This suggests that the large thermal wind exists in the 1000–850 mb layer. It is suggested that the mean geostrophic wind shear is nearly constant with height in this layer.