Papers in Meteorology and Geophysics

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The oscillatory angular motion of the snowflake is determined by a stereophotographic technique, in order to investigate the effect of the orientation of a falling snow particle on its collection efficiency.
The results are summerized as follows
1) The frequency distribution of the amplitude of oscillatory angular motion extends to about 35° but the modal amplitude lies in the region from 0° to 5°.
2) Frequency distributions of the angular velocities both about the vertical and the horizontal axis are bimodal type.
3) In the frequency distribution of the angular velocity about the vertical axis, the first modal velocity lies in the range less than 2.5 rad/sec and the second in 7.5 rad/sec to 10 rad/sec. Their mean velocity is 3.45 rad/sec.
The angular velocity less than 2.5 rad/sec has a frequency of occurrence larger than 50% and the angular velocity less than 5.0 rad/sec has one larger than 88%.
4) In the distribution of angular velocity about the horizontal axis, the first modal velocity lies in the range from 5.0 rad/sec to 7.5 rad/sec and the second in the range from 17.5 rad/sec 20.0 rad/sec. The mean velocity is 9.85 rad/sec and is about 3 times that about the vertical axis.

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A comprehensive measurement of solar radiation at the ground level was carried out by using a spectro-pyrheliometer, spectro-pyranometer and some ordinary pyranometers. Data have been accumulated since 1967 on direct solar radiation, solar aureole intensity, global and scattered sky radiation. These data were analysed to obtain some understanding of the optical properties of aerosols as one of the components of the short wave radiation balance in the atmosphere.
The extinction coeffic i e nts measured in Tokyo show the trends of gradual decreases after 1970. The amount of decrease is larger in the shorter wavelength region than in the longer. The size distributions of aerosols determined from the spectral distributions of extinction coefficients vary from case to case. The amount of particles in smaller size (r_??_0.3μm) gradually decreases from year to year and that in the larger (r_??_0.6μm)shows a slight increase in the earlier stages of the period and a rapid decrease in the later.

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