Abstract
Winds or currents at strait of Gibraltar or Simonoseki strait, whose orientation is eastwest, are prevailingly East or Nest, seldom North or South. The most noteworthy is the marked localinecrease of the wind force along the coast lying to the right of the general trend of the wind. The deflective force of the earth's rotation causes a streamline convergence along such a coast, which must be compensated by an acceleration of the wind if ascent of air shall be avoided. The north coasts of these channels will therefore be subject to strong east winds, but will have subnormal west winds (Figs. 1a and lb). Along the southcoast conditions will be intermediate. On the other hand, local cyclonic wind system is often observable there (Fig. 1c).
It is well known that cyclones weaken while crossing our islands. We could list the following possible causes: (1) The mountains may have an impeding effect on the circulation. (2) The land friction, being more than at sea, naturally would tend to decrease wind velocity. (3) The supply of water vapor must be somewhat diminished and thus slacken the speed of condensation of water vapor. Even though the Soya, Tugaru and Tusima straits are half land, still these effects must be somewhat diminished, so shat cyclones have a marked tendency to pass over these channels. The effects of local cyclonic wind system will also contribute, fascinating task to explain the real cyclone paths. A study of cyclone paths might yield results of interest. The location of the principal cyclone paths is determined on the ground that the axis of the region of greatest cyclone frequency indicates the mean position of the path (Fig. 2). The smoothed isartihms on this map represent total cyclone frequency during the period 1938. These frequencies were plotted for each 2° square of latitude and longitude. The original date were obtained from the weather maps analysed by the Central Meteorological Observatory, Tokyo, Japan. The marked tendency that cyclones pass through the Soya, Tugaru and Tusima straits is illustrated by Fig. 2 in quite satisfactory manners.
