The Lake-current and the Prevalent-wind of Lake Yamanaka in Summer. —On the Causes of the Lake-current—

Abstract

The author investigated the lake-current of Lake-Yamanaka in Yamanashi Prefecture in Japan by means of drifting bottles, ascertained the direction of the wind on the lake by observing the crooks at the tops of larch-trees and thus inquired into the relations between these two phenomena. 1) The lake-current was ascertained from the sixty four drifting bottles, the locations and times of discovery of which are known. 2) The investigation into the lake-current was made on the 4th and 5th of August, 1951, when an ideal prevalent-wind was blowing. 3) The crook at the larch-tree, top shows that from which direction the prevalent wind is blowing during May and June whice happend to be the period of their growth in this neighbourhood. 4) The results got from the meteorological observations at the Kagosaka Pass, at the Experimental Plantation Office of the Tokyo University and at Yamanaka Primary School by the lake are statistically shown in the figures 4. 5. and 6. The maximum error of 13° is found between these results and the results got from the larch-gees. 5) According to the statistics got at these meteorological observatories, the prevalent wind blows during half a year from April to September. 6) The results obtained by the author and his co-operators are shown in the figures 2 and 3. The main points are as follows;- (1) A strong south wind which has been weakened when blowing over the Kagosaka Pass blows down upon the surface of the lake and makes a wafted current over the lake, which becomes the main lake-current. (2) The main lake-current causes two big circulating currents, one winding rightward on the east side just as when you wind up a clock and the other winding leftward on the west. (3) In the eastern offing of Nagaike (a village) on the northern shore of the lake, where the main current is divided into two circulating currents…… one on the left side, and the other on the right……, the wind also shifts its direction both towards the east and towards the west, the same directions as the lake current move. This change of direction is more striking on the western side. (4) The lake current moving eastward ahead of Omama Promontary seems to be caused by the south west wind near here.