A chemical study of snow formation in the winter-monsoon season

The snow caused by the winter-monsoon in Japan was analyzed for chemical constituents, radionuclides and stable isotopes. The chloride in the snow was correlated fairly well with not only sodium of maritime origin but also calcium, sulfate and radionuclides for samples collected during a single snowfall. The rainout process seems to be prevailing over the washout process for the removal of the chemical constituents from the convective cloud. The air mass responsible for making 1 kg of snow water was calculated to be about 2000 m3 STP from the radon daughter nuclides 210Pb, 210Bi and 210po in the snow collected at Assabu, Hokkaido. The isotopic composition of the snow is not controlled directly by the temperatures of the sea surface and of the air where the snow is forming as suggested by Isono et al. (1966) but controlled by the relation among water vapor contents in the continental air and in the air transported to the Pacific and the amount of water vapor evaporated from the Japan Sea. The consistency between these results was quantitatively examined by making the budget diagram of water and chemical substances during the winter-monsoon season. (auth.)