著者

キクチ カツヒロ ウエダ ヒロシ タニグチ タカシ サトウ ノボル Katsuhiro KIKUCHI Hiroshi UYEDA Takashi TANIGUCHI Noboru SATO

雑誌

Proceedings of the NIPR Symposium on Polar Meteorology and Glaciology

巻号頁・発行日

vol.1, 1987-09

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The typical shapes of snow crystals of low temperature types that are known at present are "Gohei twins", "Sea gull", "Spearhead" and so on. Although they were named by one of the authors (K. K.) tentatively, these names appear to be accepted by scientists in the fields of cloud physics, crystal growth and so on. On the other hand, their formation mechanisms except for the gohei twin crystals have not been clarified. In this paper, the correlation between the gohei twin, sea gull, and spearhead type crystals has been considered based on a number of microphotographs taken by a polarizing microscope during the observation period from December 25,1985 to January 23,1986 at Inuvik (68°22′N, 133°42′W), N. W. T., Arctic Canada. As a result, although we have pointed out that the gohei twin type crystals are two kinds that have tip angles of 56 and 78°, they have another difference besides the difference of their tip angles. Namely, the gohei twin crystals having the tip angle of 56° have a certain kind of finlike appendages along the crystalline boundary of two extended prism planes of the crystals. On the other hand, other twin crystals that have the tip angle of 78° are devoid of finlike appendages along the crystalline boundary. The angles of 13 and 20° between two extended prism planes of the gohei twin crystals pointed out in our previous papers were clarified by the measurement of the tip angles of individual extended prism planes. Furthermore, it was noted that the gohei twin crystals that have the tip angle of 56° are similar to the spearhead type crystals, and the spearhead type crystals were one of the wings of the sea gull type crystals seen from a right angle. However, some parts of the formation mechanisms of snow crystals of low temperature types are obscure and it would be difficult to understand their exact correlation as of this report.

著者

ワダ マコト アオキ シュンジ セコ カツモト マツバラ コウジ ドイ モトヒサ ウエクボ テツロウ オカダ ケンジ カワグチ サダオ Makoto WADA Shuhji AOKI Katsumoto SEKO Kouji MATSUBARA Motohisa DOI Tetsuro UEKUBO Kenji OKADA Sadao KAWAGUCHI

雑誌

Proceedings of the NIPR Symposium on Polar Meteorology and Glaciology

巻号頁・発行日

vol.4, 1991-05

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A 5-year project of "Antarctic Climate Research (ACR)" has been started from JARE-28 in 1987. Observations of clouds and precipitation were carried out using vertical pointing radar and two microwave radiometers in 1988 (JARE-29), the second year of this project. The observations of vertical pointing radar were begun on February 24,1988,and the microwave radiometers observations were handed over to JARE-29 by JARE-28 on February 1,1988. The characteristics of the precipitation in 1988 at Syowa Station, on the coast of Antarctica, are described in this paper. Ten days variation of precipitation are calculated using radar echo intensity at 300m altitude and the relation between radar reflectivity factor (Z) and rainfall rate (R), the so-called Z-R relation. The values obtained from this method are free from the contamination of drifting snow which affects precipitation obtained by rain gauge. The result shows the maximum precipitation in autumn (February and March) and the minimum precipitation in spring (September and October). Low precipitation in spring seems to be characteristic of 1988 at Syowa Station. Snow crystals of precipitation there can be classified into three types : graupel or a heavily rimed crystals, grathering bullets, and other types of crystals such as snowflakes, dendrites and plates. The first and second types of crystals were mainly observed throughout 1988. The height of the radar echo was relatively low; namely, the echo top was under 2km in altitude, in the period when the first type of crystals mainly fell. On the other hand, in the period when the second type of crystals mainly fell, the echo top was often over 4km altitude.