Heavy snowfall in the Japan Sea coastal area of the Hokuriku district was observed when upper cold air developed anomalously and broke out towards Japan Sea. The heavy snowfall area was found at the north west side of jet stream where positive vorticity prevails. While in the lower layer, some smaller scole lows generated in a disturbance zone under the maximam positive vorticity move to the Hokuriku district and cause heavy snowfall at the coast. The author reported already the facts stated above and, in this paper, studied a threedimensional structure of the disturbance which would produce coastal heavy snowfall. From horizontal distribution at each level and zonal and meridional cross-sections of vorticity, divergence and temperature fields, it was noticed in the cases of coastal heavy snowfall that there exist descending current above the cold dome and ascending current in the lowest layer and, thus in the middle layer, there is divergent wind field in which the southerly wind at about 700mb level over Wajima seems to have important contribution.
This paper deals with rainfall distribution. The maps showing rainfall distribution in each ten days in May, June, and July are presented in relation to Stages I-IV in the rainy season, classified in Part I of this study (Yoshino 1965). It is pointed out that the rainfall zone from China to Southwest Japan is prevailing through all Stages. The appearance of the rainfall maximum over East Asia is shown on a map, which reveals an apparent northward shifting of the season in genenral. The characteristics of this rainfall are discussed in comparison with the behaviour of the frontal zone. It is important to note that the relation between the northward shifting of the frontal zone and the appearance of the rainfall maximum or the position of the rainfall zone is different in China (on 120°E), Southwest Japan (on 130°E), and Eastern Japan (140°E). The rainfall distribution in Stage III, a typical period during the rainy season, is discussed in detail.
Ice nucleus concentration in cold air-mass which came from the continent of Asia to the north-west coast of the main island of Japan in the season of north-west monsoon was observed. A close relation has been found between the fall-out rate of snow crystals or graupel pellets and the concentration of atmospheric ice nuclei active at the temperature of the tops of clouds. It is concluded that ice nuclei actually play an important role in the formation of snow crystals and graupel pellets and that their concentration controles the rate of precipitation, at least, in the case of cold convective clouds.
Electric charge of snow particles with special attention to graupel pellets was measured at several ground stations and also by means of radiosonde for measuring electric charge. Snow crystals without cloud droplets were negatlvely electrified, whereas snow flakes composed of rimed snow crystals were positively electrified. On the basis of results of the observations of electric charge of snow and experiments in laboratory, processes of electrification of snow crystals and graupel pellets in convective clouds are discussed.
A halo method (Vittori, 1956) by which one may detect chloride content above 10-13g.was applied to the measurement of chloride content in a single cloud droplet. A transparent film coated with gelatin-gel involving AgN03 was softly contacted upon a residue in a cloud droplet impacted on a Mg0 surface and an induced halo was measured under a phase-contrast microscope. By this method it is possible to observe the chloride content in a droplet with the percentage distribution for each size fraction.