起伏地形に於ける圃面の防風に就いて(3)

地形と風

抄録

The author studied the relationship between the wind and the topography, using various acutual and model landforms, from an agricultural standpoint. The investigations were carried out in a hilly district of the Atsumi Peninsula, Aiti Prefecture, establishing many observation points on summits and hillsides, in valleys and on level lands. The observations of the wind were made mainly by using Nakaasa-type anemometers and many strermers and partially with smoke. And in order to conduct investigations into the micro behaviour of the wind, some indoor model experiments were carried out using a hot wire anemometer for the measurements of the wind velocities.
Results obtained were summerized as follows:
1) The relationship between an isolated hill and the wind around it is analogous to that between an object and the movement of water flowing around it.
2) In a valley the wind generally blows along the ridges of the valley regardless of the main wind direction and its velocity slows down gradually by the influence of the topography. But if the direction of the valley coincides with that of the main wind and the valley Is outside the range of the influence of the ridge standing to windward, the wind blowing through the valley suddenly adds strength.
3) In a dale and a pass the properties of the wind differ far from those on the outside.
4) The air flow near the ground is apt to be influenced by the smallest undulation of the ground. We may turn this relation between the air flow and the undulation to the best account in preventing the wind damage in the cultivated field.
5) It is very often that the direction and velocity of the wind changes every hour. In that case the correlation between the wind and the topography changes accordingly.