During 21th to 30th June 1971, a study on the characteristics of cloud condensation nuclei was carried out, by the continuous sampling of cloud water, and by measuring the water content and size distribution of the droplets in Cu type cloud at the summit of Mt. Ibuki.
During the period, the summit was twice completely cov e red with cloud for several hours. In both cases, cloud droplets were small and numerous.
As the result of the chemical analysis of cloud water and by considering the size distribution of cloud droplets and the prevailing southerly wind during the sampling, it is inferred that the airpolluting substances from the industrialized area of Nagoya and Yokkaichi are greatly responsible for the formation of those clouds.
On the other hand, we analyzed the summer precipitation data for the pasth 40 years at Hikone Weather Station located at the foot of Mt. Ibuki. The data were classified into the prewar and the postwar daysthe prewar precipitation when the industries were not yet fully developed and the postwar period when industrialization was greatly promoted. As a result, it was found the precipitation after the war is 20-30 percent over that of the prewar period.
It is considered that such a large in c rease of precipitation in the postwar period is due to the low clouds composed of dense small cloud droplets created by polluted nuclei.
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