An experiment on the cloud modification by spraying NaCI saturated solution directly into clouds was conducted. An atomizer was set at the windward slope of a mountain, and droplets of the salt solution were introduced into clouds when the clouds were ascending along the slope and covered the observation points which were located 1800m above sea level. Marked changes in size spectrum of cloud elements and the following rapid decrease in cloud water content caused by onset of precipitation were observed. This result showed that the first stage of precipitation was induced within a few minutes by spraying a relatively small number of NaCI droplets into the cloud which had been colloidally stable.
Nickel oxide has, next to silver iodide, an excellent ice-nucleating ability (nucleation temperature, -7°C). With the intention of testing its practical applicability to rain-making, we have performed a field experiment from January 27 to February 4, 1956 on the outskirts of Takayama City, Gifu Prefecture. Nickel oxide was prepared through thermal decomposition of the carbonate, and the powder obtained was sent up, after thorough pulverization, into the sky by a dust-ejector. We have succeeded in deriving snow from the atmosphere at temperatures as low as -12° to -16°C, but never experienced, as expected, any appreciable snow-fall when the air temperature was higher than -7°C. In order to seek after the diffusion of the nickel oxide smoke in the atmosphere, we have, keeping pace with the progress of experiment, made a trial of detecting nickel oxide in the air around the seeding-station by a dimethyl glyoxime indicator method. The ice crystals whose formation is considered to be due to the seeding were fixed to replicas; they were classified according to their shape to plate-like, columnar, stellar, dendritic and so on; particularly, the size of the plate crystals was measured and it was found to range from 30 to 210μ in diameter.
In Part I, the fields of wind and temperature in Baiu season are analyzed, and the cross sections along the 140°E meridian for the period 26 to 28 June 1954 are presented. It is shown that the frontal layer in Baiu season is characterized by weaker contrast of temperature than in winter. In Part II, the water vapour content in troposphere is treated as an element for studying the structure of Baiu front. The horizontal gradient of water vapour content is comparatively large compared with that of temperature in the vicinity of the front. Moreover, the quantity of condensation is computed from the continuity equation of water vapour content and compared with the observations. The mechanism of supply of water vapour is also considered.
The deepening of cyclones formed in the East China Sea during a year of 1954 is discussed in terms of the style of the 500-mb contour patterns deduced from the Bjerknes' theory, with good results. In order to provide some concrete answers to salient contour patterns concerning the deepening of cyclones, some of the case studies are presented to illustrate surface and 500mb synoptic situations each season.
The numerical prediction scheme of precipitation is discussed in detail. First, the forecasting formula of precipitation for a small time interval is shown in comparison with Smagorinsky and Collin's formula. Second, an applied example of this method is displayed with the explanation of technique. Third, the scheme of extension of forecast period with respect to rainfall forecast is described. Fourth, the water vapour prediction is investigated, which is important for the forecast of movement of rainy region. Fifth, in connection with the above problem, the adverting wind of water vapour is tesified, especially on 1000 mb level. In this test, the surface wind is calculated considering the non-geostrophic wind component proposed by Hinkelmann. Comparison of the calculated wind with the observed leads us to the conclusion that the wind direction agrees considerably well, though the speed of the calculated wind is exceedingly larger than that of the observed.
A remarkable artificial radioactivity was found in a fallout collected at Asahikawa on April 12, 1955. Its specific activity was determined to be 2, 660cpm/g by our measurement carried out on April 22. This is equivalent to about 22.5 mμC/g. The quantity of fallout amounts to ca. 1.9g/m2. The ordinary chemical analysis was made, and it was clarified that the sample was to be a loess distributed in North China. It is also explained that the radioactivity of the sample is ascribed to the fission products yielded in an experiment of the atomic weapon carried out at Nevada, U.S.A. In addition, the result of radiochemical analysis is described.
The amount of atmospheric ozone was observed at Tokyo during the period from June 1953 to September 1955, using a cadmium photoelectric tube and a glass filter. The observations were made at about 11 a.m. on the day when there was no cloud in the direction of the sun. During this period, 217 independent observations were obtained and their absolute values were determined by a series of comparative observation with Dobson spectrophotometer (No. 52) for the period April through September 1955. With this comparative observation, it was ascertained that by the present method the amount of ozone can be measured with good accuracy. The amount of ozone shows a marked seasonal variation in respective years having the maximum value in spring and the minimum in autumn. The course of annual ozone variation and its absolute value agree well with the result obtained at Washington D.C. in 1948-1950 by S. Fritz.