Under the shadow: urbanization displaces tropical cyclone rainfall to the peri-urban regions

Cities significantly affect tropical cyclone (TC)-induced rainfall through land–atmosphere interactions. While extensive modeling analyses have demonstrated that urban land surface produces more TC rainfall over cities, direct observational evidence across multiple cities remains limited, particularly in inland areas where the risks of TC-induced extreme flooding are increasing. Here, using the high spatio-temporal resolution Stage IV gridded rainfall product, we analyze TC rainfall distributions associated with 84 landfalling TCs over 112 cities in the Contiguous United States. Our analyses revealed that in over 88% of cities, intense TC rainfall occurs predominantly outside urban cores, primarily in the left-side suburban regions relative to the dominant wind within urban boundary layer. This distinct spatial pattern emerged as a robust feature across diverse urban geographic settings. However, the preferred location of urban rainfall anomalies in suburbs varies with the urban geographic setting, owing to difference in urban dynamic turbulence conditions (such as, horizontal wind and vertical velocity). Enhanced TC rainfall tends to occur upwind areas in simple and mountainous cities but downwind areas in coastal cities. Further, we reconstructed three-dimensional TC wind fields for representative cities using radar data. We find that increased urban surface roughness weakens tangential winds and strengthens radial inflow, thereby enhancing convergence and rainfall in the left quadrants of urban core region. This urban influence tends to weaken, along with larger mean rainfall and lower spatial variability under strong ambient wind. These findings highlight an urgent need for risk management and spatial planning strategies that explicitly target vulnerable peri-urban regions, and call for the integration of aerodynamic principles into risk and urban planning frameworks to enhance resilience in future cities.