Abstract
Late in June,1961, a severe rainfall occurred in various places in Japan. The numerous data for the various meteorological elements for 12 levels of the troposphere during the heavy rain are adjusted and calculated by the electronic computer. The vertical structure of the heavy rain is analysed in detail. The large-scale pressure pattern of this heavy rain in the neighbourhood of Japan is similar to the typical pattern of heavy rain in early summer in the past. In case of heavy rain, the large-scale pressure pattern is such that the North Pacific high pressure is intense and the movement is stagnant or retrograde to westward in the lower layer of the troposphere. In the upper levels, the ridge over the North Pacific Ocean is similar to the pattern of the lower layer, and further, a typhoon appears over the sea to the south of the Japan Islands or a small-scale distrubance is formed over the Japan Islands. Such a pattern produces the most favorable conditions for the penetration of the strong southerly current into some area of the Japan Islands. In such a case, it is proposed for the vertical structure of the heavy rain that the north-south temperature gradient across the stationary Bai-u front and the subtropical or polar front is very large, and in the lower layer, a severe convergence exists along the stationary Bai-u front and also in the middle layer of the troposphere.
In the middle layer, the severe convergence is produ c ed by the confluence of the general current of the westerlies or southwesterlies and the strong southerly current. The variation of the area of the severe convergence for the middle layer and the variation of the area of the heavy rainfall correspond remarkably to each other. The equation of conservation for potential temperature is lastly discussed.
