Geographical Review of Japan
Online ISSN : 2185-1719
Print ISSN : 0016-7444
ISSN-L : 0016-7444
MECHANISM OF THE LOCAL WIND IN A SMALL VALLEY
Masatoshi YOSHINO
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JOURNAL FREE ACCESS

1952 Volume 25 Issue 11 Pages 458-461

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Abstract
The author measured the small fluctuations of the local winds affected by the topography, and found their mechanism. in a small valley (Fig. 1) at Nishiura, Shizuoka Prefecture. Observation was made on March 21, 1952, and the locations of the observed points on the cross-section of the valley are shown in the lower part of Fig. 2. Instruments were set at a height of 120cm above the ground. Using the results observed. every 1 minute at the 4 observation points, isopleths are drawn as shown in Figs. 2 and 3. Analysing these data, conclusions are abstracted as follows.
1) From the beginning to the end of the Qbservation, N-NE winds with a velocity of about 2m/s were prevailing. But calms appear at intervals of 25±3 minutes (e. g. A, B, C in Fig. 3), and weaker winds appear in the middle of their time (e. g. a, b in Fig. 3).
2) SE-SSE winds at the station No. 2 blow 3_??_4 minutes after the calms or weaker winds, and stronger NE winds (>3m/s) blow 1_??_2 minutes after the, SE-SSE winds. Therefore, we consider that the down-valley SE-SSE winds blow at regular intervals when the prevailing E-NE winds become calm or weaker.
3) So, it can be concluded that the sea breezes or the valley winds blowing N-NE at the valley bottom and NE-E at the valley slope have a periodicity at the observed time under small pressure gradient and in fine weather.
4) Mean wind directions and their variance manifested as a confidence interval at every station are calculated as shown in Table 1. The Variance at station No. 4 is two times greater than each of those of the other stations.
5) The gustiness of wind speed _??_ of every 10 minutes, their mean for 1 hour and their variances at all stations are given in Table 2. The greatest varience is found at station No. 2. It is remarkable that the station having the greatest variance of the wind velocity does not coincide with the station having that of the wind direction.
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© The Association of Japanese Gergraphers
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