Analysis on applicability of morphology methods in the estimation of aerodynamic parameter of urban areas in Shanghai

The aerodynamic parameters at Fengxian, Qingpu and Baoshan sites with a radius of 1 km from the gradient observations at gradient towers in Shanghai are estimated and analyzed by 4 morphometric methods (Rt, Ra, Ma, Ka) using surface morphometric parameters. The results estimated by different morphometric methods and the sensitivity to morphometric parameters are then analyzed and compared with aerodynamic parameters calculated by dynamic method (Lw) based on gradient observation of the tower. The results are as follows. (1) Both the values and the distribution of the aerodynamic parameters calculated by morphometric methods are different compared to the ones by dynamic method. Firstly, the value of zero-plane displacement calculated by morphometric method is smaller than the one by Lw method, while the one by Ka method is closest to Lw method among 4 morphometric methods. The differences in roughness length by dynamic and morphological methods are relatively small, and the results of Ma and Ka are similar to those of Lw. (2) By comparing the sensitivity of the four morphological methods to the related input parameters, we conclude that the Ka method is the most sensitive to building height, building height change rate and building layout. Firstly, the aerodynamic parameters by Ka method is highly sensitive to z_Hmax, σ_H and z_H, where z_d is more sensitive to the non-uniform distribution of building height, while z₀ is more sensitive to z_H. Secondly, the Ka method is highly sensitive to λ_F and λ_P, that is, sensitive to the building layout in the studied areas. (3) By comparison with the dynamic method results, the scheme 1 of Ka method (Ka_M1) is considered to be the most suitable morphometric method for estimation of aerodynamic parameters of the typical city of Shanghai studied here. In addition, the Rt method can be used as an alternative to the calculation and analysis of aerodynamic parameters in the case of lacking observation and morphological data.