Studies on the Snow Crystals of Low Temperature Types and Arctic Aerosols

为完成文武会国际科学研究项目“低温型雪晶与北极气溶胶研究”的实地考察，我们于1989年12月13日至1990年1月28日在格陵兰岛哥德哈芬“北极站”（69 15′n, 53 34′w）和哥德哈布“生物站”（64 10′n, 51 45′w）进行了实地观测。虽然格陵兰地区的气温条件相对高于正常值，但在两个观测点进行的观测相当成功。在5 ~ -22.5ºC的温度条件下，观测到“Goheitwin”、“Seagull”、“Spearhead”等低温型雪晶。特别是海鸥型和尖头型晶体被大量观察到。因此，我们能够比较在Godhavn观测到的晶体的特征和在加拿大北极和挪威北部观测到的晶体的特征。另一方面，在gothab的0 ~ 15ºC的空气温度条件下，观测到大量的霰颗粒。因此，我们可以比较北极地区西格陵兰岛和温带地区日本群岛西海岸霰粒子的气候特征。特别是比较霰粒子的胚胎是雪晶还是冰冻的云滴，是非常有趣的。对低温型雪晶的形成机理进行了研究，并根据在极地地区拍摄的显微照片和实验室实验结果进行了探讨。因此，认为尖头型晶体的形成机制类似于立方结构模型与基面上旋转孪晶相结合的gohei孪晶。对这次野外观测所得的资料进行了积极的分析。

For the accomplishment of the Field Research of the Monbusho International Scientific Research Program under the title of "Studies on the Snow Crystals of Low Temperature Types and Arctic Aerosols", we have carried out the field observations at "The Arctic Station", Godhavn (69ﾟ15'N, 53ﾟ34'W) and "The Biological Station", Godthab (64ﾟ10'N, 51ﾟ45'W), Greenland from December 13, 1989 to January 28, 1990.Although the air temperature conditions in the Greenland area was relatively higher than the normal value, the observations carried out at two observation sites were quite successful. Because, a number of snow crystals of low temperature types, "Goheitwin", "Seagull" and "Spearhead" types were observed under the air temperature conditions from 5ﾟC to -22.5ﾟC at Godhavn. Especially, the seagull and spearhead type crystals were observed numerously. Therefore, we are able to compare the characteristics of the crystals observed at Godhavn and that observed at the Arctic Canada and the Northern Norway.On the other hand, a number of graupel particles were observed under the air temperature conditions from 0ﾟC to -15ﾟC at Godthab. Therefore, we are able to compare the climatological characteristics of graupel particles of the Western Greenland in Arctic regions to that of the western coast of Japan Islands in the temperate regions. Especially, it is very interesting in comparing whether the embryo of graupel particles is a snow crystal or a frozen cloud droplet.Concerning to the snow crystals of low temperature types, the formation mechanisms were considered based on a number of microphotographs taken in the polar regions and obtained in laboratory experiments. As a result, it is considered that the formation mechanism of the spearhead type crystals is similar to that of the gohei twin typecrystals which is a combination of cubic structure model and a rotation twin on the basal face.The data obtained in this field observations are analyzing energetically.