The system of partial differe n tial equations which shows the one-dimensional unsteady airflow over the mountains under the inversion layer is hyperbolic type, and has two families of characteristic lines. Using this nature, the system of basic equations is integrated numerically along each characteristic line. The following three initial conditions are given: (1) subcritical flow for all intervals, (2) subcritical flow for all intervals, but critical flow at the mountain crest, and (3) supercritical flow for all intervals. In all cases the bight of the inversion increases on the windward side and decreases on lee side. And a jump arises on the lee side after some time-steps. The higher the initial speed, the farther downward the jump appears, which suggests the possibility of a fall wind. That the swell is higher with increasing initial speed explains the abnormal pressure difference between the windward and the lee side. In order to determine the position of the lee side jump, a method for extending the characteristic lines through the jump region is devised and described. Some characteristics of propagation of the jump or drop whose shape is unchanged are discussed analytically. These analytical results can explain the propagation of the disturbances observed in numerical solutions.
In order to study the secula r variations of various rainfall amounts quantitatively, the next three methods are taken into consideration; a. Trend inspection based on rank correlational procedure. b. Fitting the orthogonal polynominals to secular variation. c. Statistical quantities showing variability and per s istence. Yearly, monthly and special rainfall amounts were statistically analysed by using the electronic computer, and we obtained the following main results through geographical comparison of the statistical quantities: (i) Over the whole area of Japan, there are more widely increasing regions than decreasing regions. (ii) Conspicuous increasing trends can be seen at Kylisha and Shikoku districts. (iii) Both increasing and decreasing trends are seen disorder at To-hoku and Hokuriku districts, and rather apparent increasing regions i n snowfall amount are scattered over these districts. (iv) Decreasing trend can be seen at Kanto district for any kinds of rainfall amounts on the whole. As a result, the q u alitative explanations hitherto put forward by several authors have been revised quantitatively and more in detail, and some of them are more or less corrected in this paper.
The author made the tide predictions for 53 tide gage stations on the coast of Japanese Islands by means of 30 constituents, the tidal constants of which were taken by the same harmonic analysis technique, and investigated the accuracy and the natures of errors in predictions using the power spectrum of the residuals. For stations on the coast directly facing the open sea, the predictions amount to about 95% of the astronomical tides. In general this will be satisfactory but more exact predictions are needed for such coasts as that of Ariake Bay where the tide range is more than four meters. Especially in Osaka Bay and the Inland Sea, the accuracy of the predictions is less under the influence of tidal non-linear interactions, and the predictions could represent only abut 90% of the astronomical tides. The nature of predictional error is clarified by means of the power spectrum of the residuals.
Earthquake spectra before a n d after the Matsushiro Swarm, that were obtained at Matsushiro Station from local earthquakes of the same hypocentral region and of the same order of magnitude, showed a marked difference. Before the swarm, waves higher than 200 cps were abundantly recorded, whereas such high-frequency waves almost disappeared toward the end of the swarm. The present study revealed that the change in spctrum was due to the medium, which was highly fractured by an enormous number of earthquakes during the swarm, and that the attenuation of highfrequency energy in the seismic waves, which are propagated through the swarm region, is caused by scattering by many fissures. It seems likely that the Matsushiro region of hig h heterogeneity was under strain, started breaking by many fractures, and was eventually released from the strain as MoGw's experiments suggested.
First, it is pointed out that t he spacial and the time distribution of aftershock activities are closely related. Then, the distributions of time interval of successive shocks in the initial and later stages are chiefly studied, and the following results are obtained: ( 1 ) In the later stage of aftershock activity, the occurrence of shocks shows a random tendency in both space and time as pointed out in the previous papers. ( 2 ) On the other hand, in the initial stage of the activity, where the parameter c of the modified OMORI formula n(t)=A/(t+c)p plays an important role, the time distribution of shocks shows a clustering tendency corresponding to the same tendency in space as pointed out in the previous paper.
A new instrument improved in some points was constructed. Using this instrument measurements of direct solar radiation and au r e o l e intensity were performed. From the measurements of direct solar radiation, the spectral distribution of optical thickness of aerosol particles was obtained for each measurement. The spectral distributions obtained are classified into three types. The size distribution of aerosol particles corresponding to each spectral distribution of optical thickness is inferred for each measurement, by comparing with the theoretical calculations by FOITZIK and DEIRMENDJIAN. The size distribution inferred is the power law distribution with a hollow in the shorter side and a hump in the longer side of the range of radius. The wavelength region corresponding to the hollow and th e hump are dependent on the type of spectral distribution of optical thickness. Intensities of aureole at angular distance θ smaller than 5 deg. from the sun increase with increasing wavelength and those for θ>10 deg. are flat or slightly decrease with increasing wavelength. The ratio of monochromatic aureole intensity to that of the Rayleigh atmosphere increases with increasing turbidity factor T(λ)=[τ-M(λ)+τ R(λ)]τR(λ). The slopes of angular distributions of aureolein tensities corresponding to the three types of τM(2) are different from each othe rand the slope for type I is the largest among them. The dependency of slopes of the angular distributions on wavelength widely varies for each measure-. ment. The relation between the angular distribution and the siz e d i stribution of aerosol particles were also investigated by using the two in dices, that is, F= τM(0.4μ)/τM(0.8μ)-M(0.8μ)/τM(1.6μ)andAD=Iγ(1.5μ,θ)/γ(0.4μ,θ).
The content of plutonium in sea water collected in the western North Pacific off Japan was determined. Plutonium was analyzed by the a-ray spectrometric method after isolating it from a large volume of sea water by hydroxide coprecipitation and an anion exchanger. The plutonium content in sea water ranged from 1.8 to 22.6x 10-15 g/l in the surface waters. Even in the intermediate or deep waters, comparatively high concentration of plutonium was determined. The ratio of 238Pu/289Pu ranged from 7 to 28%.