抄録
Ice crystals in the air or ice-needles were observed at Hailar, Manchuria(49&13'N,119&44'E,619.0m), especially, crystal forms and some physical properties were studied by means of microphotograpy. It was found that the greater part of the ice crystals in the air are formed in the lower atmosphere, less than 400 meters in height.
1) On the average, the ice crystals were observed on 45.4days in a winter at Hailar (Table 1). The mean temperature, mean of maximum temperature, mean of minimum temperature, absolute maximum temperature, absolute minimum temperature, and the number of days on which ice crystals were seen at Hailar for each month of the year are shown in Table 2. Ice crystals were observed from November to March only. The relation between mean temperature and the number of days with ice crystals are shown in Fig.1, where this relation is expressed by an almost straight in annual mean. But as shown in Fig.2 and 4, these individual points are distributed unsytematically. The distribution of the number of days with ice crystals in North Manchuria is shown in Fig.3.
Ice crystals were observed frequently in north-western part of Manchuria, and at Hsingan most frequently. The daily change of ice crystals is shown in Fig.5, the maximum frequency is observed at 8-10o'clock.
2) The relation to air temperature (Table 4), to vapour pressure (Table 5), to wind direction and velocity (Table 6), and to cloud amount (Table 7) were also studied.
