Based on the analyses of weather maps of scales from local through Asiatic to northern hemispheric, the author studies in this paper some mesoclimatological problems of the mesoscale disturbances observed during the period of heavy snow in the Hokuriku District. The main problems treated are as follows:- First, the statistical characters of the so-called plain heavy snow free from mountain effect and of mountain heavy snow are examined. According to the statistics on the frequency of heavy snowfalls for 9 winters from 1953 to 1961, mountain heavy snow is the most frequent, accounting for more than half of the total occurrences. On the contrary, the frequency of plain snow is comparatively low, as the mean occurrence of plain snow is only 2.5 days during one winter season. Plain heavy snow is mainly related to the bulge of isobars on the weather chart in which a cold vortex is located over the Japan Sea. Especially it seems that, under the prevalence of the bulge pressure pattern, there occur heavy snow and rainfall, thunderstorms and gusts with the passing of a mesoscale disturbance, throughout the year. Therefore this pressure pattern has great importance in forecasting severe storms around the Japan Sea side of the Japanese mainland.
Basing on ship observations over the Japan Sea area, the relations are investigated statistically between cloud amount and heat or moisture supply estimated by the bulk method for the January situation of the 5 year period 1963-1967. A significant positive correlation is found particularly over the central part of the Japan Sea area where cumulus clouds start to form and develop. The relation seems to be clear under a north to northwesterly monsoon situation.
A numerical experiment for the study of the development and the structure of tropical cyclones is performed with a 13-layer model. The total amount of latent heat released in a vertical column of air is specified by the horizontal mass convergence in the friction layer, as proposed by Ooyama (1964). The vertical distribution of released latent heat is assumed to be proportional to the temperature difference between cumulus clouds and large scale field (Yamasaki,1968b). For simplicity, the equivalent potential temperature of cumulus clouds is kept constant with time and space. The numerical experiment sh o ws that the present tropical cyclone model is capable of describing many features observed in actual tropical cyclones, if initial conditions (especially the initial static stability) and various physical parameters are chosen appropriately. The structure and the developmental process of the simulated tropical cyclone are discussed in detail.
New instruments were des i gned for measuring the liquid water content in clouds and fogs. Their principles are based on the capture of water droplets on a synthetic filament moving in the cloud air. The technique is useful for measurement in all kinds of clod: supercooled, nonsupercooled and ice clouds. The instruments were developed into three types, that is, for aircraft, radiosonde and ground use. These instruments will enable us to measure the liquid w a ter content at intervals of any time range from 1 to 30 seconds. The measurements of the liquid water content are described which were carried- out in supercooled clouds and river fogs by using these instruments.
The writers' previous repo r t (1968) has revealed that the seasonal variation of mortality can be classified into the summer concentration type for Egypt, the winter concentration type for Japan and England, and the “deseasonality” type for the United States and the Scandinavian countries. Taking for instance the infant mortality in the City of New York, they attempt in this paper to make an intensive study into the last-named phenomenonthe considerable moderation of seasonal variation or deseasonality and its historical process of formation. (Then is presented a series of models for mortalitytemperature correlation decade by decade in Japan.) Correlation graphs by the decade for infa n t mortality and temperature in New York, in addition to the convariance, analysis, point out the steady decline of the infant death rate, the gradual disapperance of seasonal differences in mortality, and the formation and levelling-off of nearly linear regression for spring and autumnthe quantitative process of slowing-down in the seasonal variation of mortality or deseasonality. Responsible for all this are, among others, the reduction of deaths from infectious diseases in winter and the favorable effect of central heating. The corresponding correlation graphs for Tokyo present a striking contrast to those for the American city. Taking for instance Japan's total mortality, the authors h a ve prepared models for mortality-temperature correlation by the decade in the past six decades. From the 1900's through the 1930's, there are two upcurves, one in summer and the other in winter, and the gradual diminution of the summer area of distribution make a contrast with the enlargement of the winter one. In the 1950's, the summer upcurve flattens out, whereas the winter peak gets higher and the winter area becomes larger. It is also noteworthy that the point of intersection for spring and autumn regression curves rises in temperature decade after decade, and that the two curves closely approach each other in the 1960's, without, however, crossing each other. In conclusion, the causes of such chrono logical changes are studied decade by decade. They differ widely from decade to decade, and in each decade there are specific factors for bulging or flattening. Infectious and old-age diseases are responsible for the bulging upcurve in summer in the 1900's; the arrest of the infectious diseases i n the hot season accounts for the termination of the summer peak, an d two smaller bulges appear in the 1920's and 1930's; and the winter high peak in the 1950's and 1960's is ascribed to the concentration of deaths mainly from apoplexy and other old age diseases.
The vertical structure of the aerosol content observed by a lidarin the lower atmosphere is to be related to the thermal structureof the atmosphere, but no definite relationship has yet been foundbetween lidar and radiosonde data in spite of many suggestions madeconcerning this subject since the advent of lidar. Some investigationis here made on it by the use of lidar data obtained only on cleardays with light winds. Aerosol particles are found in late afternoon to be accumulatedby atmospheric convection in the upper levels (700-1,600 meters orso), of which the boundary is mostly determined by the maximummixing depth obtained with the help of the temperature profile givenby radiosonde ascent and the maximum surface temperature. Lidarobservations clearly visualize the atmospheric convection throughtracers of aerosol particles. Both in the morning and in early afternoonit is seen that the “plume” or “flare” is one of the main formsin the convection. The vertical distributions of aerosols both in themorning and in the afternoon are characterized and classified inview of the convection based on the lidar data. Many discontinuities of lidar echoes are found to be presentthroughout the lower atmosphere in the form of either large layersor solitary patches ; they are considered to be important in the "layerreflection"in the microwave propagation.
The Volcano Mihara-yama in Izu-Oshima Island is an active volcano situated about 110 km SSW from Tokyo. At this volcano, Strombolian type eruptions have been taking place frequently since ancient times, and volcanic tremors continually occur at the crater. In this paper, the writer investigates the relationships among volcanic actions, volcanic tremors and volcanic earthquakes of the Volcano Mihara-yama, based on the data obtained at the Oshima Weather Station, during the period from 1938 to 1968. In this period, seismometrical observations at the Oshima Volcano were carried out continuously or temporarily at 5 points in Oshima Island. The distribution of the observation stations, the types and constants of the seismographs and the observed periods are shown in Fig.1, Table 1and Table 2. All the seismographs are of the displacement type. Since 1965, the efficient electromagnetic seismographs have been in use in addition to the old mechanical ones in the seismometrical network for this volcano. Consequently, new types of volcanic tremors and volcanic earthquakes closely related to the volcanic activities have been found.