The Riming Proportion in Snow Particles Falling on Coastal Areas

Abstract

When studying snow-particle formation and precipitation mechanisms, it is important to examine the ratio of the contribution of each process-such as deposition, riming, and aggregation-to the growth of a snow particle. In the winter monsoon season, measurements were made of the contribution ratio of the riming process to snow-particle growth by the method of Harimaya and Sato (1989). Snowfall in which the riming process was predominant in the growth of snow particles (i.e. snowfall having a rime mass of more than 50 % of the total mass) accounted for about 70 % of total snowfall frequency along the coastal areas toward the Japan Sea. Over the coastal areas, the deposition process did not contribute to strong snowfall intensity, being controlled instead by the riming process.
It has generally been considered that snow clouds in the developing and mature stages pass over coastal areas more frequently than over inland areas, as snow clouds move from the sea toward the land. It has been observed that the riming process was predominant during the developing and mature stages of snow clouds. It follows from these that the riming process is predominant in snowfall along coastal areas where such snow clouds often pass.