Regional Differences in Snowflake Size Distributions

Field observations were carried out to clarify the regional differences in snowflake size distributions and the causes for these differences. When snowflake size distributions can be approximately expressed by the exponential distribution ND = N0 exp(-λD), the intercept parameter N0 in different regions of Japan, becomes larger according to the distance from the coast, even under the condition of equal snowfall intensity. This information can be interpreted by the idea that supercooled cloud droplets predominate in the snow clouds initially, while the phase change from water to ice advances as the clouds move inland. The slope λ of the size distributions in the central Japan group is more gentle than that in the northern Japan group, since the adhesion strength of snow crystals is strong under the warmer condition.