A Method for Observation of Falling Snow Particles

Abstract

The shadow photograph method was applied to obtain a record of the form, size and mass of snow crystals. The apparatue for this method is very simple and is shown in Fig. 1. Illuminating the glass plate G, on which many snow crystals were received, from above with a small electric torch bulb L for a few seconds, the shadow of crystals is taken directly as a shadow photograph on the photographic paper in the cassette C. Such a shadow photograph is a record of the form and size of snow crystals on the glass. By heating the glass plate mildly, the individual snow crystals are melted into hemispherical droplets. A shadow photograph of these droplets is taken in the same way as above, and gives a record of the mass of the original crystals.
By this method, about fifty pairs of records for various kinds of snow crystal shapes were obtained on Mt. Taisetsu in Hokkaidô, in February 1953. The relation between the mass and the dimension of snow crystals was sought from these records. Excepting the case of plane dendritic crystals, the results coincide fairly well with the results of the empirical formulas obtained by Nakaya and Terada. And on this occasion, the empirical formulas for stellar and columnar crystals are newly obtained.