WIND PROFILES AND ROUGHNESS LENGTHS OVER BEIJING CITY

Roughness lengths and wind profiles over an urban landscape in Beijing, China and their relationship with surface geometric features have been investigated by utilizing a whole-year Beijing 325-m Meteorological Tower data. Preliminary results show that a clear rough-to-smooth transition can be seen in the velocity profile. In addition, wind directions above 63 m are densely distributed with the prevailing winds coming from northwest and southwest, while those below are strongly disordered. Finally, roughness lengths derived from the lower profiles respond well to local surface characteristics and their fetches are generally within an area of 500-m radius