Volcanoes as a Source of Atmospheric Ice Nuclei

Abstract

IN order to determine the nature and the concentration of ice-forming nuclei in the atmosphere, which are considered to play an important part in the initiation of rain, we have been carrying out, in Tokyo since April, measurements of the concentration of ice nuclei by means of an ice nuclei counter similar to that of Bigg¹. The concentration is measured at temperatures of −13° C. −15° C. and −20° C. It was found² that the concentration of ice nuclei was low in maritime air masses and high in the air masses which reached Japan from arid or semi-arid regions of the continent of Asia. Very high concentration in spring was found to be associated with the arrival of dust consisting of loess particles originating from the ground of the arid region of north China. The result of our experimenton loess particles which fell in Japan shows that they are effective as ice nuclei at temperatures below −13° C. Despite the general tendency already mentioned, the concentration of ice nuclei in the atmosphere increased occasionally even in maritime air masses.