Analytical prediction of urban wind profiles in densely built-up areas using a combined method of WRF and a porosity model

Abstract

Mesoscale modeling such as Weather Research and Forecasting (WRF) simulations are not sufficiently precise to predict wind profiles in densely built-up areas, and existing improvement methods remain computationally expensive and time-consuming. To efficiently and accurately estimate wind profiles in densely built-up areas, this study proposed a method that combines WRF with a porosity model. WRF provides the wind profile at the urban edge, and the porosity model calculates the airflow pressure drop across the selected urban area using a parametrized urban layout. The urban wind profile is then analytically determined with the momentum integral method. The performance of the proposed method was first evaluated in three generic urban layouts, with validated computational fluid dynamics (CFD) simulations used as benchmarks. The proposed method was then applied in a real urban layout to demonstrate its performance, and the Kowloon district of Hong Kong, with an area of $\mathrm{2,350}m\times 643m$, was selected as the target area. The wind profile measured with a radiosonde in the same region was used as a benchmark. For comparison, the wind profile directly extracted from the WRF simulation within the densely built-up area was also included. The results showed that the method accurately estimated wind profiles in the generic urban layouts. In the real urban layout, the proposed method estimated the urban wind profile reasonably well in the densely built-up area with complex building configurations and performed better than WRF.