Impact of Heterogeneous Urban Morphology on Distributions of Typhoon-Induced Rainfall

Studying the impact of heterogeneous urban surfaces on typhoon precipitation is important for refined disaster forecasting. In this paper, a heavy rainfall induced by Typhoon Lekima (2019) in Shanghai, China was simulated by using the Weather Research and Forecasting (WRF) model. The simulation incorporated the Local Climate Zone (LCZ) land use data that match with complex urban morphological parameters, and the results were compared to those from a control case based on the MODIS (Moderate-resolution Imaging Spectroradiometer) land use data with simple urban morphology. Significant improvements in simulating the spatial distribution of rainfall are found after the heterogeneity of urban morphology was incorporated. Stronger frictional and dragging effects in the high-rise building area gave rise to a reduction in horizontal wind speed at low levels, impacted the local vorticity, accumulation of moisture, and local precipitation potential. Generally, the rainfall mainly accumulated in the urban–rural crossover area. The reduction of rainfall and a rebound at a later time in the high-rise buildings area are indicative of the significant suppressive and lagging effect of the urban morphology, with complex urban morphology reproducing more realistic rainfall distributions.