One of the most important causes for snowfall over the Japanese Islands in winter is associated with the transformation of continental polar air-masses during passage over the Japan Sea. The cP air-masses are rapidly modified over the relatively warm water owing to the addition of sensible and latent heat. The theory of air-mass transformation due to eddy diffusions is re-examined by taking account of the phase change of water vapor and the variable exchange coefficient dependent on the static stability. Numerical experiments are made to test the model. It is shown that the present simple model can describe the average weather condition over the Japan Sea in winter, if the variation of exchange coefficients in the model is taken into consideration.
The results of numerical weather prediction based on the quasi-geostrophic equations with vanishing p-velocities both at the top and bottom of the troposphere appear to indicate that the propagation speeds of waves in the upper troposphere are too large and the east-ward speeds of waves (of medium length) in the lower troposphere are too small in com-parison with those observed. In this paper, perturbation analyses for the two-level geos-trophic equations are made for the following two sets of boundary conditions, (i) ωT (=p- velocity at the top of the troposphere) is proportional to the height-change at the upper level and ωs (=p-velocity at the bottom of the troposphere) vanishes, (ii) ωT vanishes, whereas ωs is proportional to the height-change at the lower level. The result indicates that the phase speed of waves at the upper level in case (i) is smaller than that in case of vanishing ωT, whereas the phase speed of waves at the lower level in case (ii) is smaller than that in case of vanishing ωs.
An analysis is made of available observations on the electrical properties of natural and artificial snowstorms. An explanation for this electrification is given in terms of the Latham-Mason theory of charge transfer associated with temperature gradients in ice. Experiments show that the electrification of blowing snow is intimately related to the temperature gradients in the snow surface at the time of disruption ; the charge acquired by the large and small blown snow particles is explicable qualitatively in terms of the temperature-gradient theory.
Two-dimensional non-steady viscous flow around a circular cylinder is investigated by solving the exact two-dimensional Navier-Stokes equations numerically for Reynolds numbers (Re) of 40 and 100. When Re is 40, a steady state solution can exist. On the other hand, when Re is 100, flow pattern does not become steady and the Karman vortex street appears. In the computations performed, these features are successfully realized, and the evolution of flow pattern of Kármán vortex is obtained. The quantity ∨‘⋅∇∨’ is also calculated for the purpose of studying the mechanism of dissipation of the vortex in the downstream side of the obstacle. The flow patterns as well as the drag coefficients obtained are in good agreement with the experimental data in both cases. In solving the problem using a finite domain, physical and computational boundary conditions should be posed properly. The method used was proved to be fairly satisfactory, if the domain is wide enough to contain the wake occuring behind the cylinder.
From harmonic analysis of the 500mb height data obtained from 20°N to 80°N at intervals of 10° latitude during the thousand day period of the ten winters from 1947/48 to 1956/57, some statistical features of amplitudes and phase angles of the 500mb heights are derived for wave number one to six and the results are presented. The symbols adopted in this paper are given in Section 2. The negative correlation between zonal mean 5-day mean surface pressures at 70°N and 35°N has been discussed by Willett (1960) and Lorenz (1951). This applies also to the daily 500mb heights, giving the maximum negative correlation coefficient -0.568 between Δz (40°N) and Δz (70°N) as shown in Table 1. This correlation coefficient varies from year to year with the range about 0.2 around the mean value -0.568 as shown by the full line in Fig. 1. The dotted line in Fig. 1 is the correlation coefficient between the 5-day mean surface pressures p(35°N) and p(70°N) in winter half year obtained by Willett (1960). The parallelism of the two curves shows that the negative correlation for the 500mb heights is related to the meridional shift of the atmospheric mass in the northern hemisphere. The meridional distribution of the amplitudes and the standard deviation of their anomaly are shown in Fig. 2 and Fig. 3 for n=1 to 6 respectively. The maximum of both of them shifts to the lower latitudes with increasing wave number. Correlation coefficients between the anomalies of amplitudes at each latitudes are pre-sented in Table 1 and partly in Fig. 4. It is seen from the table that the correlation is generally poor at two latitudes 20 degrees or more apart except for n=2 and 3. The maximum of correlation coefficient between the amplitudes at two latitudes 10 degrees apart shifts to the low latitudes with increasing wave number as can be seen in Fig. 4. The frequency distribution of phase angles is shown in Fig. 5. The distribution of φ1 indicates that the maximum frequency shifts eastward with increasing latitude, as already shown by Barrett (1958) for the 300mb height and the project AROWA for the 500mb height. The distribution of φ2 shows also the shifts of the maximum frequency, but in this case, two homogeneous zones in the higher and the lower latitudes are recognized. That is to say, the phase angle in the higher latitudes is about 180 degrees out of the one in the lower latitudes. This is reflected in the fact that the frequency distributions of φ2 are different at high, normal and low index stages of ΔU55N as shown in Fig. 6. At the high index stage two homogeneous zones in the higher and the lower latitudes are significant. At the low index stage, however, the shift of φ2 is clearly seen. On the other hand, the frequency distributions for n_??_4 are rather flat compared with those for n_??_3 as can be found in Fig. 5. In Fig. 7, the distributions of phase velocities, defined by the phase difference in con-secutive two days, are presented at 50°N for n=1 to 6 at high (dotted line), normal (thin full line) and low index (heavy full line) stages of U50N. The linear relationship does not exist between the phase velocities and U50N for n_??_3, but it is more pronounced for the higher wave number and most significant for n=6. The result described above indicates that the ultra long waves n_??_3 predominate to the north of the middle latitudes and the long waves n_??_5 in the middle or low latitudes, with the critical wave number four. This statistical fact may be taken into consideration in the theoretical studies such as model researches.
A cold room has been constructed whose temperature can be varied over the range +20°C to -60°C and inside which an experimenter can work. The humidity, wind-speed, pressure and electric field strength inside the room can be controlled to cover the ranges of importance in the atmosphere. The large size of the room makes it possible for realistic simulation of atmospheric processes to be made inside it.