The Structure of Surface Winds Crossing over a Small Valley

Abstract

The observations of surface winds crossing over a valley were made in detail, taking account of the various characters according to the cross-section shape of the valley. The 30 minutes mean wind speed, its decreasing rate at the shadow side and the exposed side of the valley slope, the intensity of turbulence, the mean wind direction, analysis with the aid of isopleths, and the formation processes of the eddies and up-valley winds in the valley were studied from a microclimatological viewpoint. The important results obtained are: the highly correlated experimental equations which connect the decreasing rate of mean wind speed and the valley topography, the difference of relationships between √u'² and the mean wind speed at the respective side of the valley slope from that at the flat horizontal surface, the clear distinction between mean wind speed and directions in the deep valley from those in the shallow one, and the cyclic deformation of the eddies in the valley.