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Show [ Journal of the Faculty of Science, Hokkaido University, Japan, Ser. VII, Vol. II, No. 4, 1966] Meteorological Classification of Natural Snow Crystals Choji ' MAGONO and Chung Woo LEE ( Received Aug. 23, 1966) Abstract From a meteorological point of view, Nakaya's classification of natural snow crystals was modified and supplemented. By this improvement of the classification, the certain inconveniences in the description of crystal shapes of natural snow crystals were removed, particularly in unsymmetrical or irregular shapes. By the use of this improved classification, the temperature and vapor supply conditions for the growth of various kinds of natural snow crystals were described. The conditions were determined by meteorological observation methods. It may be seen that the conditions are very similar to Nakaya's Ta- s diagram. This means that the Nakaya's diagram is applicable to the formation of natural snow crystals. 1. Introduction Nakaya's1* general classification of snow crystals was a most perfect classification for natural snow crystals from a physical point of view, and the result of his investigation of the artificial snow crystals, namely, the Ta- s diagram was described by the classification method. Gold and Power2), Murai3) and Grunow4>, 5> reported that Nakaya's diagram was roughly applicable to the formation of natural snow crystals. The diagram was further studied and improved by Nakaya, Hanajima and Muguruma6), Hallett and Mason7) and Kobayashi8>. 9>. 10>. With these improvements, it may be expected that there is a possibility that the present improved diagram will be useful as a more exact and detailed indicator of temperature and humidity of a cloud in which snow crystals are formed. In the recent ten years, Magono and his colleagues11'. 12), 13) continued their observation of natural snow crystals in Hokkaido from a meteorological point of view. At first Nakaya's classification method to describe the shape of snow crystals was used, but they found that his classification was insufficient to describe the meteorological difference in the type of snow crystals, because the classification was too simple in the group of unsymmetric or modified types, although it is in good detail in the group of regular types. In actual cases, most of snow crystals are irregular, unsymmetric, modified or rimed. |