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.
By making use of 4-level quasi-geostrophic model, the numerical forecasts over the period of 72-hrs are examined. In this model, the effects of the latent heat release due to the condensation and also the transport of sensible heat between the ocean and the atmosphere are taken into consideration. In order to avoid the truncation error in the finite-difference equations of the vorticity equation and the thermodynamic equation, we use the special computational scheme. The result of numerical forecasts shows that the diabatic model mentioned above represents the atmospheric motion pretty well. The statistical results of the forecast are compared with those of adiabatic model during the period over 1962-1964.
Using geopotential data for three levels of 500mb, 100mb and 50mb during three month period from December 1957 to February 1958, the daily estimates have been made for the zonal mean wind, the zonal mean temperature, the momentum and sensible heat transports due to disturbances, and the zonal mean vertical velocity, to examine the variation of these quantities with respect to three phases before, during and after the warming phenomenon. The spectral forms of the energy equations have been employed to discuss the energetics of dominant waves with wave numbers 1 and 2 in the stratospheric layer between 100mb and 50mb. From the measurements of the energy interaction terms, it was recognized that a rapid and large increase of the eddy kinetic energy for these waves was neither due to the barotropic nor due to the baroclinic instability. The following conclusion seems to be sure : the initial growth of the warming disturbances was accomplished, to a great extent, by vertical energy transfer across the upper and lower boundaries.
The monthly mean 500mb and 100mb charts were studied to investigate the relationship between the subtropical anticyclone in the troposphere over the Pacific and the anticyclone in the lower stratosphere over Southern Asia, which has recently come into notice. At 500mb, the western cell of subtropical anticyclone in the Pacific lies over the so-called Ogasawara anticyclone at the surface, and the center of the cell moves from south to north as the summer season progresses. At 100mb, the anticyclonic area extending east from the anticyclone centered over Southern Asia in summer is laid over the Ogasawara anticyclone at the surface. Further, the formation of closed high on the 100mb level occurs over the Western Pacific in spring, then the center moves toward west and reaches the Tibet Plateau in August. It was found that, when the first formation of this closed high on the 100mb chart takes place over the oceanic area far south to Japan in April, the departure of isobaric height from the normal on the monthly mean 500mb chart in the Western Pacific in August of this year becomes positive, and when the stratospheric high forms first over the South China Sea, the departure becomes negative.