On the Incipient Stages of Snow Crystals

[摘要] Supercooled water clouds often contain minute snow crystals, 10_??_100μ in size, which are considered to be the incipient stages of growth. The author collected about 200 photomicrographs of those crystals at the observatories of Mt. Fuji and Mt. Ibuki, and investigated the relation between their crystal forms and the air temperatures at the time when observed. The columnar forms were always observed at the temperatures above -10°C, and the tabular forms below-9°C. The observed temperature ranges of various crystal forms are shown in the table. These results are nearly consistent with the case of artificial snow.The author concludes that all snow crystals are, at the first stage of its formation, perfect crystals of 10μ in size, which undergo different skeletal growth corresponding to the temperature, i, e. in the direction of principal axis above -10°C, and in the direction of secondary axes below -10°C. The temperature range of most rapid growth parallel to the secondary axes is -12.5_??_-15°C. This is by 1_??_2°C higher than that of dendritic form of artificial snow.

[学科分类] 大气科学