Numerical analysis and forecasting with fine mesh is compared with that with coarse mesh in the case of synoptic situations of severe rain. The models used for the comparison are 4-layer quasigeostrophic dry and wet models. In the numerical analysis and prediction with fine mesh of 150 km, a vertical velocity field of medium scale can be detected in regions corresponding to severe rainfall, except the rainfall area following large-scale motions. On the other hand, in the analysis and prediction with coarse mesh of 300 km, no vertical velocity field of medium scale is detected. And furthermore analysis is made of synoptic situations of such scale. Synoptic analysis is discussed in view of thermal fields, vertical stabilities, vertical motions and surface frontal activities with various vertical cross sections.
The raindrop data obtained at three stations 3.4,2.1 and 1.3 km above sea level (a.s.l.) along the Mt. Fuji slope were evidently under a warm rain situation, and compared with those at Hawaii (FUJIWARA,1967). The comparison resulted in good agreement in that the spectra are very narrow with extremely high concentrations and that accordingly both parameters B and β in Z-R relationship are excessively small. Although with the Hawaiian data a tendency was found that the mean values of both parameters decreased with height, since the topographical slope was gentle (about 3/100), some doubt remained as to whether this tendency is due to the height or to the horizontal distance. This doubt is almost removed by the present result for which the network extended vertically and horizontally to a comparable order of distance (about 1/2 of slope).
Taking stereographical photographs of falling snow particles with a stroboflash, the author has investigated statistically the motion of snow particles in a population in order to determine the collisionrate of snow particles, and then proceeded to the study of the formation of snowflakes based on the collision-rate thus obtained. Part I: The motions of individual snow particles falling through the still air were studied using a stereographical method. It was found that the horizontal meandering motion of the snow particle was related with the aerodynamic lift force on it. Part II: The statistical features of motions of snow particles were investigated. On this basis the collision-rates of snow particles are calculated. Part III: The mechanisms of snowflake formation are discussed based on SMOLUCHOWSKI's equations. It is concluded that i) the stage of the snowflake formation is divided into two types. The first-type collision is one due to the random motion of snow particles, and the second-type collision due to difference in the mean velocity of individual snow particles. ii) it is necessary for the formation of further larger snowflakes to keep up the supply of individual snow crystals for a suitable time. Part IV: In order to investigate the riming process of snowflakes, models of snowflake, the surfaces of which were coated with MgO, were set in the air flow in a vertical wind tunnel. The trajectories of water droplets sprayed into the air flow were determined from the photographs of the moving droplets. The features of capture of droplets were discussed.