Precipitation samples collected on rain occasions with and without hail have been chemically analysed for Cl-, SO4--, Na+, K+ and Ca++. Higher ionic concentrations were noted in rain water when the rain occasion was associated with hail than when it was not. The
finding helps corroborate Ludlam's (1958) suggestion that hail embryos form on giant hygroscopic aerosols.
It has been recently recognized that the role played by organized cumulus-scale convec-tion is very important in understanding the dynamics of the general circulation of the atmosphere, particularly in the tropics. Because of large differences between the size of cumulus-scale convection and of large-scale motion, it is difficult to deal with both pheno-mena in one system of atmospheric equations. In this paper we discuss (1) the effects of an ensemble of convective elements on the large-scale motion, and (2) the influence of the large-scale motion on the development of organized cumulus clouds. A scheme is proposed to solve simultaneously two systems of equations for the large-scale flow and for the cumulus-scale convection. The effects of cumu-lus convection are included in the equations for the large-scale motions. The large-scale (synoptic) conditions are included in the equations for the cumulus convection which determine not only the structure of cumulus clouds, but also the population of the clouds.
The intimate relation between the activity of the cumulus convections and the mesoscale convergence fie'd is studied over the coastal area of the Japan Sea on January 19, 1965 by using the data of the “Heavy Snow Storm Research Project” which includes the aerial photographic cloud observation and maritime observation in addition to the radar, aerologi-cal and surface observations, The remarkable fact is that the activity of the cumulus is strongly controlled by the mesoscale convergence field, i.e. the well-developed cumuli exist only in the area of con-vergence of more than 10-4sec-1. The roles of the cumulus convection are discussed concerning the dynamical balance of the mesoscale disturbance and mixing effects on the momentum and heat distribution.
The mesoscale warm area is often observed in the lower part of the unstable air column lying in the central part of a cold dome which is passing the Japan Islands across the Japan Sea. It is closely related to mesoscale disturbances which develop in the vicinity of a cold dome center. It seems reasonable to imply that the cumulus convections caused by the predominant transport of sensible and latent heat from the warm sea surface are activated within the mesoscale convergent wind field and exert an effect of warming just above the condensation level.
It has been observed that when ice crystals are nucleated on fine threads in a low-pressure diffusion chamber, they grow preferentially upward and sublimate downward leaving, between crystals and threads, thin filaments and sheets of ice. The features and growth process of these structures are presently studied. Filaments and edges of sheets have a typical shape, formed by a nearly periodical series of “beads” and “necks ”. During growth, new beads appear at the base of the filaments, while all the structure looks as if it were rising up against the vapour flux. The phenome-non is explained by considering an alternate process of condensation upward and evaporation downward of the ice surface, due to the uni-directional vapour flux. It is shown that the vapour density in the region where filaments form is near to equi-librium, and the typical shape of “beads” and “necks” is related to the compensating effect of the different equilibrium vapour pressure at their surfaces, due to their different curvature. The interpretation of the present phenomenon may be applied to explain the formationof ice filaments observed in more general conditions.
A tropical cumulonimbus cloud over the Malayan Peninsula was studied by means of the stereophotogrammetry. After three dimensional analysis of the cloud, the following results were obtained : 1) Intermittent updrafts in Cb clouds developed into a petal like form and a hole was observed at the top. 2) An anticyclonical sucking action by the cumulonimbus cloud was observed at an altitude of 4 to 5km, that is, just above the level of low cumulus cloud.
The distribution of the atmospheric refractive index was observed repeatedly at eleva-tions up to 3Km over the course between Tokyo and Sendai. UHF propagation experiment was also conducted over the 310Km land-path between Tokyo and Sendai. Considering the effect of mountain wave which was caused by the gently sloped mountain ridge near the midpoint of the course, meteorological interpretation was made on both the observed N-profiles and the spatial distribution of ΔN2. The influence of the airflow across a mountain ridge on the variation of the UHF transmission loss, L, was also investigated by the use of the upper meteorological data. Correlation between the observed hourly median values of L and the relative values of the scattering cross section, a, estimated by the upper meteorological data is fairly good.