Wind Speed Profiles of the Lowest Air Layer under Influences of Micro-topography

[摘要] To make clear influences of micro-topography on the wind structure near the ground, the variation of wind speed with height up to 5 meter above the ground was observed at various stations situated on the flat open land, and on the side slopes or in the bottom of the small valley. Differences of the profiles from the so-called logarithmic law were evident. The types of the profiles were grouped roughly into three types according to their micro-topographic situation. When the prevailing wind flows at right angle to the running direction of the small valley having steep side slopes, maximum of wind speed at 2-3 meter above the ground appeared on the lower part of the valley slope or in the valley bottom, owing to the counter flow of the lower part of eddies formed in the valley. The counter flow had some twisted characters with the direction of mountain or valley wind and the ratio of its speed to that of the prevailing wind showed a relation to the prevailing wind speed and the time of day.

[学科分类] 大气科学