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

Studying the impact of heterogeneous urban surfaces on typhoon-induced precipitation is important for refined disaster forecasting. In this work, heavy rainfall induced by the Typhoon Lekima (2019) in Shanghai, China was simulated by using the Weather Research and Forecasting (WRF) model. The simulation incorporated local climate zone (LCZ) land use data that resolved complex urban morphological parameters, and the results were compared with those from a control case study based on Moderate Resolution Imaging Spectroradiometer (MODIS) land use data with simple urban morphological features. Significant improvements in simulating the spatial distribution of rainfall were found after the heterogeneity of urban morphology was incorporated into the simulation model. Stronger frictional and drag effects in high-rise building areas resulted in a reduction in horizontal low-level wind speed, which impacted local vorticity, the accumulation of moisture, and local precipitation potential. Generally, rainfall mainly accumulated in areas with urban–rural crossover. The early reduction in rainfall and a rebound at a later time in high-rise building areas are indicative of the significant suppressive and lag effects of urban morphological features, with more realistic rainfall distributions obtained with the incorporation of complex urban morphological features.