Cloud Droplets and Rain Drops Collected and Frozen on Natural Snow Crystals

[摘要] During a period of observation of snow crystals at Inuvik (68°22'N, 133°42'W), N.W.T., Canada, rimed snow crystals, snow crystals with small frozen rain drops and ice pellets were observed for a period of several days. It was found that even when the diameters of frozen cloud droplets were larger than 40μ, sometimes a considerable number of them were single crystals. The average size of polycrystalline frozen cloud droplets was larger by 20 to 30% than that of the single crystal frozen cloud droplets. Whenever the polycrystalline frozen cloud droplets prevailed there were water saturation layers aloft with air temperature below -15°C. Although the shape of snow crystal was spatial dendritic type, 80 to 90% of frozen cloud droplets were single crystal with the same axis to substrate snow crystal. The spatial branches were found to grow from the part where the number of polycrystalline and single crystal droplets with different axis to substrate snow crystals were large.Small frozen rain drops and snow crystals with small frozen rain drops of 200μm to 300μm in diameter were observed. Although the frozen cloud droplets on the surface of snow crystals were single crystal with 80% or more with the same axis to substrate snow crystal, 60% or more of coexisting frozen rain drops on the surface of the snow crystals and free falling frozen rain drops were polycrystalline. Mean diameter of the polycrystalline frozen rain drops was larger by 20% to 30% than that of single crystal frozen rain drops. This tendency was similar to that of frozen cloud droplets.

[学科分类] 大气科学