城市近地层湍流特征分析

Turbulence characteristics in the urban surface layer

利用中国科学院大气物理研究所在北京的325 m铁塔观测资料,本文分析了47、140和280 m三个高度的湍流统计特征。结果表明,城市近地层的湍流速度方差和湍流温度方差都较好地满足局地相似关系,140 m和280 m的湍流特征非常接近,而47 m的湍流特征与之相比表现出明显的差异,说明由于城市冠层动力和热力非均匀性的影响,粗糙子层和惯性子层的湍流特性不同,其相应的参数化方案也应该不同。

Observational data from Beijing 325 m meteorological tower are used to investigate the turbulence characteristics in the urban surface layer.The turbulent variances at three levels of 47 m,140 m and 280 m heights are analyzed in the frame of the local similarity theory.The results show that the variances of wind velocity and temperature can be quite well described by the local similarity theory.However,the comparison shows that the turbulence characteristics at 140 m and 280 m heights are close to each other,while the turbulence characteristics at 47 m height are different from them.These results indicate that,since the turbulence properties in the roughness sublayer are strongly influenced by the dynamical and thermal heterogeneity of urban canopy,they are different to those in the inertial sublayer.And the turbulence statistics in the roughness sublayer and the inertial sublayer should be described by the different schemes.