PREVAILING WINDS IN THE KONSEN-GENYA, SOUTHEASTERN HOKKAIDO

Abstract

In this study, the distributions of the direction and velocity of the prevailing winds in Konsen-Genya, Southeastern Hokkaido, were made clear by using results of field observation and available wind data. First, investigations were carried out on the distribution of prevailing wind directions and wind velocity observed at fourteen agrometeorological stations in Konsen-Genya. Secondly, field observation were made on wind-shaped trees in order to make clear the detailed distribution of the prevailing winds and local wind conditions. The grade of defor-mation and the direction of deformation of wind-shaped larch trees (Larix leptolepis) were measured at about 100 points in August, 1972. The results obtained in this study are summarized as follows: In summer: (1) The southerly winds from the Pacific Ocean blow up to north along the Kushiro river. (2) The southerly winds from the Pacific Ocean blow up to north in the central part of the Konsen-Genya, and then gradually change the direction northeastwards along the Shibetsu mountains and one branch of the southerly winds flows northwestwards from the Nemuro Bay. (3) The easterly winds from the Nemuro Bay blow into the lowland along the Shibetsu and the Nishibetsu Rivers. Their easterly border runs on the eastern side of the Kenebetsu, Nishishunbetsu and Chanai regions. (4) The strongest wind region is found on the coast and the weak wind prevails in the Shibecha, Arekinai and Ota regions. In winter: (1) The northerly winds blow from the Sea of Okhotsk to Pacific Ocean on the lowland area along the Kushiro River. (2) One branch of the northerly winds blows southeastwards between the Nishibetsu moun-tains and the Shibetsu mountains. (3) The westerly winds blow from the Kenebetsu and Nishishunbetsu regions to the Nemuro Bay. (4) The strongest wind region is found in the lowland along the Kushiro River as well as in the Shibetsu region. The border of the region with strong prevailing winds estimated from wind-shaped trees in winter runs in the Nishibetsu and Nishishunbetsu regions. Further, an attempt was made to clarify the relation between the mean wind velocity of the prevailing wind in summer at the thirteen agrometeorological stations and the grade of wind-shaped trees of Larix leptolepis in the Ishikari Plain, the Shari-Abashiri region and Konsen-Genya. The result is represented by the following equation: Ws=1.6+0.95 Gsl where, Ws: mean wind velocity (m/s) observed at the meteorological stations in summer, and Gsl: grade of wind-shaped trees of Larix leptolepis in summer. This means that the mean wind velocity in summer (m/s) is approximately equal to the value adding 1.4_??_1.6 to the grade value of wind-shaped larch tree.