The Nature and the Origin of Ice Nuclei in the .Atmosphere

Abstract

Concentrations of ice-nuclei active at temperatures of -13°C, -15°C and -20°C were observed with an ice-nucleus counter in Tokyo, Japan. The concentrations varied from day to day in a wide range. Generally, higher concentrations occurred on days when air came from the continent of Asia and low concentrations occurred when air came from the Pacific Ocean. Abnormally high concentrations were observed when air reached Japan from the arid regions of North China and Mongolia where heavy dust storms occurred in front of cold fronts. Although the ice nuclei concentration was low in maritime airmass, sometimes high values were observed. This was found to be associated with volcanic eruptions. Possibility of production of ice nuclei from sea-spray is also discussed. The ice-forming abilites of volcanic ash from ten active volcanoes in Japan, of dust (loess) particles from North China which fell in Japan, and of soil particles and stone meteorite were determined in laboratory. It is concluded that the principal active ice nuclei in the atmosphere are some kinds of soil particles (especially, clay minerals) blown up from arid regions and volcanic dust from active volcanoes.