1966 Volume 44 Issue 4 Pages 218-226
Ice nucleus concentration in cold air-mass which came from the continent of Asia to the north-west coast of the main island of Japan in the season of north-west monsoon was observed. A close relation has been found between the fall-out rate of snow crystals or graupel pellets and the concentration of atmospheric ice nuclei active at the temperature of the tops of clouds. It is concluded that ice nuclei actually play an important role in the formation of snow crystals and graupel pellets and that their concentration controles the rate of precipitation, at least, in the case of cold convective clouds.