Observation of the angular distribution of ultraviolet sky radiation in the principal meridian plane were made at the summit of Mt. Fuji and at Tokyo by means of a photoelectric cell and filters mounted on a theodolite when it was almost at the sunset and also when the sun's altitude was 30°. Regarding the observed relative intensities at various zenith distances, relatively high values at larger zenith angle were pointed out either when the wave-length of measured radiation was the shorter one or when the elevation of observing place was the higher one. These were both attributed to the effect of decreasing optical thickness of the scattering atmosphere which had already been discussed by the present author. An investigation on the effect of the ozone layer was done by observing the intensity ratio of the two different ranges of U. V. sky radiation at the zenith. The well-known “Umkehr Effect” was observed, thus showing a possibility of observing the ozone layer by means of this sort of apparatus.
From the point of view of the numerical prediction in the barotropic model, the movement of the cyclone is studied. Removing an adequate circular vortex from the weather chart of a cyclone, the interaction between the vortex and the residual field is studied theoretically. Furthermore, the velocity of the movement of the height minimum (the centre of the cyclone) on the constant pressure chart is derived from the height change obtained by analysis, and it is also shown by a real example that this method is objective, that is, the velocity thus obtained is uniquely determined in spite of the various circular vortices eliminated. The purpose of this paper is twofold; one is to make clear the dynamical role of the barotropic model of cyclones and the other is to give a basic aspect to the prediction of the movement of typhoons (next paper).
The mass-distribution of raindrops and solid precipitation elements produced by Northwest Monsoon was observed by the photographic method at Shiozawa in midwinter, 1953, and it was found that the distribution of raindrops or small snow particles is exactly reprented by Marshall and Palmer's formula, but that of snow flakes is extremely different from their formula. In the case of the precipitation which included snow flakes, the distritribution of small precipitation elements was smaller than that shown by Marshall and Palmer's formula, but on the contrary that of snow flakes was much larger than that represented by their formula. And many snow flakes of equivalent diameter larger than 4mm were measured, although raindrops observed in the period were all smaller than 2mm in diameter. From these results, it was suggested that the snow flakes would split in falling before they melt into raindrops.
It is conceivable that the volcanic eruption is one of the important sources which supply ice-forming nuclei and large condensation nuclei for the atmosphere. We have found statistically that volcanic eruptions of Mt. Asama had a close relation to the precipitation in its neighbouring districts, and experiments showed that volcanic dust particles of this mountain were effective as ice-forming nuclei at temperatures below -14°C. These statistical and experimental results show that volcanic dust particles are important nuclei in the atmosphere and increase the amount of precipitation.