The Angle of Deflection between the Mean Vector of the Surface Wind and the Geostrophic Wind Vector over Central Japan

[摘要] An attempt was made to survey the angle of deflection between the surface wind vector (Vs)-the vector mean wind over central Japan, obtained by vectorially averaging the surface wind values at 270 AMeDAS stations-and the geostrophic wind vector (Vg) directly calculated from the surface pressure differences among four stations around central Japan.The value of the mean deflection angle between the two directions was 76 degrees (from Vg to Vs, measured counterclockwise), a relatively large value compared with other studies. The critical direction of Vg, at which the deflection angle significantly changed, was found to occur around ENE. To investigate this critical direction, an attempt was made to relate the angle to surface airflow patterns. It was concluded that the critical direction corresponded to a significant direction of Vg which divides the surface airflow pattern into two categories: the airflow patterns with prevailing NW winds and with prevailing NE winds over the surface of the Kanto plain.The angle of deflection and the wind speed ratio υs/υg were discussed and compared with the results of previous studies.

[学科分类] 大气科学