Merits and demerits of the direct measurements of evaporation from a lake by pan and of the indirect estimation by the turbulent transfer theory from measurements of wind, temperature and humidity profiles, were discussed based on some measurements. As a result, the practical estimation of evaporation from Lake Towada was carried out by means of the turbulent transfer theory based on observations of water temperature and of wind velocity, temperature and humidity at 3 m high above the lake surface, made at a represen-tative place on the lake. The amount of evaporation in a year was estimated to be 902 mm, and the annual variation of evaporation was found to be against our expectation ; evaporation was greater in cold season from September to March than in warm season from April to August.
An annual atmospheric oscillation due to thermal excitations around the stratopause is discussed in connection with the observed intense heating of the winter polar upper meso-sphere. The result shows at least qualitatively that the heating may be explained as a dynamic heating associated with the general circulation in the upper atmosphere. The annual variations of zonal and meridional wind systems are discussed together with the heating.
When a system of the primitive equations of motion, the thermodynamic equation andthe continuity equation is expressed in the nondimensional form, the Rossby number and the Richardson number will appear in the coefficients of these equations as parameters. It is well known that when the solutions of the system are expanded into the power series of the Rossby number, zero order solutions of the Rossby number correspond to the quasi-geostrophic solutions. But in this paper, it is shown by using the linearized system that the exact criterion of the baroclinic instability is determined by the first order solutions which is one order higher than the quasi-geostrophic solutions. It is also shown that when the horizontal gradient of the static stability in the basic current is taken into account, unstable waves exist in both the very long and the very short wavelength regions, besides the well-known unstable wavelength region.
The air in an expansion chamber was expanded in fairly slow speed through different each filter to change the cooling rate of air. Size distributions and concentrations of activated droplets thus obtained were examined and the selection effect was found out on the concentrations according to the cooling rate and initial dew point. An empirical formula was presented on the concentrations of droplets and the constant in the size distribution after Best was decided from these results. The mixed distribution of condensation nuclei (soluble and insoluble) in the test air are presumed to illustrate the produced flat size distributions.
Photographic observations were carried out on the spatial concentration of falling snow particles. Photographs were taken by 8 mm cine camera at the rate of 16 frames a minute. The main results are described as follows : 1) The frequency of each concentration which is classified by 10-particle difference, was obtained in the shower and continuous types of snowfall. The distribution curve of frequency may be explained from a general compound Poisson's distribution in the case of shower, while it is represented approximately as a Gaussian distribution in the cese of continuous one. 2) In the case of snow shower, the probability density function of cells that their average spatial concentration lies between λ and λ+dλ was obtained, where λ is the concen-tration averaged on each cell. It may be thought that the probability distribution function consists of two curves : one of them has a steeper and larger maximum value than the other one, which may be thought Gaussian distribution in form, at low concentration. This result illustrates that the former corresponds to the distribution curve of original cells and the latter is due to snow particles blown down from neighbouring trees and roofs of huts. 3) Auto-correlations were calculated from the fluctuation of spatial concentration in both cases.