First, the amount of both sensible and latent energy exchange between the Japan Sea and the atmosphere during winter were computed based upon the balance requirement of energy in the atmosphere. The detailed explanations about the method adopted here were made in the preceding paper about the modification of airmass over the Japan Sea during the period of typical outburst of cold continental air (12). The mean amount of supplied heat during January and February 1955 thus obtained is as much as 555 cal/cm2/day, though it is considerably smaller than that during the period of typical outburst of cold air at the end of December. 1954 (1030 cal/cm2/day). On the other hand, the mean amount of evaporation during winter is about 5.6mm/day which corresponds to 340 cal/cm2/day, and is considerably smaller than that of sensible heat, though the Bowen's ratio (6) is nearly equal to unity over the Japan Sea during this season. Finally in order to verify these results, the amount of energy exchange was estimated based upon the balance requirement of the energy of sea water.
The ionizations byα-, β-, γ- rays and β-, γ- rays and the natural radioactive dust concentration in the atmosphere near the ground have been observed continuously at Tanashi, Tokyo, from April 1958. On fine days, the diurnal variation of the ionization by α-, β-, γ- rays is similar to that of the ionization by β-, γ-rays. The maximum value occurs at night (4-6h), and the minimum in the daytime (11-13 h). On cloudy and rainy days, the time variations are very irregular and the values are considerably larger than those on fine days. On fine days, the values of (β/γ)/(αβγ) are about 2-5 per cent, being large in the daytime and small at night, but the values on cloudy and rainy days are considerably smaller than those on fine days. According to the results of observations with an electrostatic precipitator the natural radioactive dust concentration is large at night and small in the daytime, and the diurnal variation being similar to that of ionization. But, the amplitude of the diurnal variation curve of the dust concentration collected with the electrostatic precipitator is remarkably larger than that of the ionization by β-, γ- rays measured with an ionization chamber. The results of simultaneous observations mentioned above seem to be important for the researches on the natural radioactivity and on the frequency distribution of the particle size of the radioactive dusts in the atmosphere. The abnormal increase of the ionization by α-, β-, γ- rays was found during the solar eclipse, 19 Apr., 1958. The maximum value occurred at the time of the maximum obscuration, and was over twice that on the other days.
In order to make clear the process of energy production in a tropical cyclone, Typhoon “Harriet” is studied during its stage of decay and transformation into an extratropical cyclone. Analysing the temperature field, it is shown that the thermal structure changes from the symmetric to the asymmetric configuration and that the horizontal extent of the warm core decreases. From the analysis of the surface wind field, the velocity convergence is computed, and some characteristic features of its distribution are described. The intensification of the surface front near the typhoon in later stages is discussed from the standpoint of kinematics. From the expectation that the modification of the structure might cause some changes in production rate of kinetic energy, the correlation between the temperature at 700mb level and the surface convergence, and also the amount of the work done by difference of the geopotential between the inner and the outer region are estimated. The result shows that the correlation changed such that it makes the production rate of kinetic energy increased, whereas the amount of the work is remarkably decreased.
Sizes of about 167, 000 raindrops in 31 rainfalls are measured by filter paper method. The time-average distributions of raindrops with size during about an hour of each rainfall are examined and classified into four types, according as in what degree they are discrepant with the equivalent Marshall-Palmer distribution which has equal rate of rainfall to them. A-type shows the distribution almost similar to the equivalent M-P-distribution except the deficiency of drops smaller than 1.4mm in diameter. B-type shows the excess of drops larger than about 1.8mm, especially at the largest end of dropsizes, and remarkable deficiency of drops smaller than about 1.6mm. Notwith-standing the excess of relatively large drops, the rain of this type has slight rate of precipitation, not exceeding 3mm/hr. C-type shows the excess of middle size drops in comparison with the equivalent M-P-distribution. D-type shows the excess of drops smaller than 1.4mm as compared with the equivalent M-P-distribution.
Correlations between integrated run-off (in terms of hydro-electric potential out-put KWh) and mean air-temperature during winter extending over the period of fifteen years are discussed for two districts in Japan. Integrated run-off during winter runs closely parallel to the mean air-temperature year by year in the Tohoku district (γ=+0.83, see Figs. 1 and 2) whose mean air-temperature in winter is nearly 0°C (i.e. melting point): while no marked correlation between integrated run-off and mean air-temperature during winter exists in Hokkaido, whose mean air-temperature in winter is quite low as -6°-7°C. Data for hydro-electric potential out-put shown in Tables 1 and 2 are taken from a source book published by the Ministry of International Trade and Industry, Japan.