利用255m铁塔研究城市化对地面粗糙度的影响

Research of Urbanization on Surface Roughness with 255m Meteorological Tower

利用天津255m气象塔近10年观测资料,采用风速梯度资料拟合对数风速廓线的方法,定量计算天津255m气象塔空气动力学粗糙度随下垫面的改变情况。结果表明各方位的粗糙度存在明显差异,偏北方向的粗糙度大于偏南方向,但各方位粗糙度在总体是逐年递增趋势,个别年代减小与城市改造有关,粗糙度与城市建筑群高度之间存在线性关系。同时利用冬季风廓线资料研究城市化对边界层风场结构的影响:结果表明受下垫面影响近地面风向逐年趋于紊乱,平均风速呈逐年递减趋势,十年间城市冠层厚度增加10m,2005年城市冠层厚度在40～60m之间。

Based on the data obtained from the Tianjin 255m meteorological tower in recent 10 years, the surface roughness was estimated by using logarithmic wind profile under the condition of neutral stratification. The results show that the surface roughness is increasing with the development of the urbanization in recent decades. The increased amplitude of the surface roughness over urban land surface is not the same in different azimuth, which is accorded with the urban construction speed. At the same time, the effect of urbanization on the urban wind field structure was studied. It shows that wind direction especially near the ground is affected most, and the wind speed, especially near the ground, decreased year by year. The thickness of urban canopy increased 10 m during the last 10 years, and now is between 40-60m.