ON SNOW CRYSTALS OF "DOUBLE GOHEI TWIN" TYPE

概要

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Observations of snow crystals of low temperature types were carried out at Alta (69°56'N, 23°16'E) and Kautokeino (69°01'N, 23°03'E), Finnmarksvidda, Norway from December 17,1987 to January 31,1988. As a result, a peculiar shape of snow crystals of low temperature types was observed at both observation sites on January 1 and 10,1988. The external shape of this crystal closely resembles that of the gohei twin types. However, the crystal grows from a center nucleus to both sides. Therefore, the crystal was named "Double Gohei Twin" types. Considering the growth mechanism of snow crystals of this type, we were reminded of our laboratory experiments carried out about ten years ago. Based on the experiments, it is understood easily that if the airborne ice fragments come in contact with the surface of supercooled cloud droplets, some of the droplets are frozen in a twin type manner. If one of the snow crystals was grown from the frozen droplets under the temperature conditions in which the column types are suitable to grow, the crystal might grow the double gohei twin type, rarely.