The acidity of snowfalls and its variation through the processes of accumulation and melting

Abstract

This study is concerned with the characteristics of acidity of snowfalls brought by the northwesterly winter monsoons, low pressure systems and other disturbances around Sapporo, Hokkaido, Japan. Samplings of daily snowfalls were carried out from January 1 to March 31, 1991 in Sapporo. Falling snow crystals, whole depth of snow cover, depth of snow layers formed by each snowfall, and snowmelt water existing snow cover were measured through a period of accumulation and melting of snow cover. Snowfalls brought by the northwesterly winter monsoon winds had relatively lower pH values and higher electrical conductivity than those brought by low pressure systems. The acidity of the whole depth of snow cover did not vary greatly before the snowmelt period. The acidity of each snow layer, however, indicated characteristic variations closely connected with metamorphism of the accumulated snow cover. During the observation period, the acidity of daily snowmelt water which had run off from snow cover showed the greatest ion concentrations in the first stage of the snowmelt season. Concentrations of chemical constituents of snow cover had drastically decreased and acidity had approached neutrality at the peak of the snowmelt season. The cause of this seems to be the large quantity of chemical constituents which run off snow cover for a short time during the first stage of the snowmelt season. © 1995, Meteorological Society of Japan.