雪結晶の結晶形と電荷符号について

Abstract

Some observations in the field of cloud physics and atmospheric electricity were carried out when the author was a member of the wintering party of the 9th Japanese Antarctic Research Expedition at Syowa Station, Antarctica throughout the whole year from February 1968 to January 1969. Especially, a simultaneous observation of electric charges on natural falling snow crystals, the shapes of snow crystals and electric field strength were selected from a view point of importance and interest of the charge generation in clouds.As a result, a very interesting phenomenon was found in which the electric polarity of snow crystals of dendrite, sector and plate was negative and the polarity of snow crystals of column, combination of bullets and side plane was positive. Taking into account that the temperature range of the growth of dendrite, sector and plate is roughly between -10°C and -20°C and that of the other three shapes of snow crystals are between -20°C and -35°C, it would be appropriate to assume a positive polarity of a thundercloud and other electrified clouds with solid precipitation particles. In other words, it may be considered that negative and positive charge centers in the cloud volume are located around the -15°C level and the -25°C to - 35°C level, respectively. These temperature ranges coincide with Takahashi's observation (1965) using an electric charge sonde, in which he reported that positive charged particles were observed at a temperature range between -18°C and -39°C and negative charged particles were present at a range between 0°C and -18°C.