2004 Volume 48 Pages 139-144
We investigate shear functions for momentum (φM-1) and heat (φH-1) and linear correlation coefficients of them (-ruw |rwT|) using data acquired over an urban surface layer in Tokyo Japan. Field measurement was conducted on a 29m height tower, 4 times the canopy height of 7.3m. 3D sonic anemometers were installed at 4 heights in the region 1.5zh<z<4zh and fine wire thermocouples were mounted at 10 heights from the ground to the top. Main conclusions were obtained as follows.(1) Momentum flux decreases with height. Non-dimensional horizontal wind velocity follows a conventional stratified logarithmic profile when it is scaled by the shear stress extrapolated to the roof top level. However, the locally scaled wind profile fails the agreement.(2) Both of φM-1 and -ruw have the dependency on height and they are enhanced near the canopy due to the ‘bluff body’ effect.(3) At a height of z/zh =2.7, φM-1 follows the conventional similarity function while -ruw is still larger than a conventional one. The ‘bluff body’ effect appears more significantly in -ruw.(4) Both of ΦH-1 and |rwT| have a good agreement with the conventional function and the dependencies on height are not found. In the case of heat, the conventional similarity theory can be applied to the urban surface layer.
