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

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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.