A Physical Study of Solid Precipitation from Convective Clouds over the Sea: Part IV

[摘要] The observation at the coast of and over the Japan Sea revealed as follows; (a) the amounts of sodium and chlorine in graupel pellets were several times as large as those in snow flakes, and the ratio of Na to Cl in the graupel was very close to that in the sea water, (b) a number of supercooled large cloud drops (several tens of microns in diameter) were present in clouds over the sea near the coast, where graupel showers occurred very often, (c) there was a positive correlation between the daily amount of snowfall and the concentration of giant chloride particles in the air, (d) the relation between NH4+ content and Na+ content of snow shower from convective cells formed over the sea was different from that of snow shower from orographic cells at an inland area.It may be concluded that these results provide the evidence for the importance of giant sea salt particles in the formation of snowfall from convective cells over the sea. The role of the giant salt particles was probably to enhance the growth of rimed snow crystals. Owing to the large relative fall velocity of the rimed snow crystals, they collected a number of ice crystals and formed snow flakes. Thus, a kind of colloidal stability of ice clouds where all ice crystals had nearly the same slow fall velocity could be destroyed and the substantial snowfall would be formed.

[学科分类] 大气科学