On the Seasonal Variation of Upper air current over Tokyo as revealed by the Observation of Cirri Clouds

[摘要] The author observed clouds with his new nephoscope for 450 days from February 1924 to June 1925. The observation for August of 1924 is missed. The frequency of cirrus drift in each ten degrees of azimuth during the whole period was shown in Fig. 1. (p. 317). The maximum frequency occurred in the interval of 260°-270° of Azimuth i. e. a little south of west, amounting 25.5% of the total frequency 278, of which 270 have west and 8 have east component of drift. The mean velocity for each month was shown in Fig. 2. (p. 317) which shows the remarkable contrast between summer and winter values. As well known, the velocity of travel of cyclonic centers in this vicinity is fast in winter and slow in summer. This fact may be explained to some degree from the upper air current and stands in concordance with the observation of Th. Hesselberg. The angles of deviation of the direction of the upper cloud drift from west was averaged for NW and SW quadrant for month to month. The result was shown in Fig. 3. (p. 318). The deviation was great in summer and less in winter, the average velocity of the cloud drift in various directions for four seasons is shown in Fig. 4. In winter the drift from between W and NW. is weaker than the drift from between W and SW. In summer there is no special preference between NW and SW.

[学科分类] 大气科学