Four Stages of the Rainy Season in Early Summer over East Asia (Part II)

Abstract

The rainy season in early summer over East Asia was divided into four stages by considering the positions of frontal zones at sea level and the features of westerly zonal winds at the 500-mb level detected on the isopleth charts along 120°E and 140°E. The chronicle of Stages I-IV for each ten days in May, June and July, 1950-1963, was first given. Secondly, the macro-scale situations of each Stage, such as the patterns of 500-mb contours over the northern hemisphere, the patterns of zonal winds at 500-mb level over East Asia, the vertical profiles of zonal winds along 140°E and the positions of frontal zones at 850-mb level, were described by compiling the states for respective Stages. According to these maps and profiles, it can be found that the situations in Stage I were a winter type, those from Stage II showed a type of summer character and a true summer type appeared in Stage IV. Finally, the results of present division were compared with the others' to deal with the regional and time differences in the beginning and the end of the rainy season in connection with Stages I-IV.