Atmospheric Electrical Properties of Snow Clouds with Precipitation

Abstract

Simultaneous observations of the surface electric field, shape and charge on snow crystals and melted diameters of the crystals were carried out at the seashore of Ishikari near Sapporo where snow clouds of falling snow accompanied by northwesterly winds were observed during the winter monsoon season.
From the observational results, it was confirmed that in general dendritic crystals were negatively charged under a positive electric field and relatively large dendritic snowflakes, densely rimed crystals and soft hail were positively charged under a negative electric field. Furthermore, it was found that when positive snow crystals fell, the mode value of the size distribution of melted diameter at that moment shifted to smaller values as compared with that when negative snow crystals fell alone. Therefore, it was considered that snowflakes and densely rimed crystals were positively charged when small fragments were torn off from fragile flakes and crystals during their descent and at such times small fragments acquired negative charges. Moreover, suspended small fragments acquired negative charges when they collided with the falling flakes and crystals. As a result, the main crystals acquired positive charges as a matter of course.