Impacts of Urban Heat and Surface Roughness on Landfalling Tropical Cyclone Intensity: A Case Study Based on TC Victor (1997) in Coastal South China

Abstract

This study investigates the impacts of urban‐induced anthropogenic heat (AH) and surface roughness on Tropical Cyclone (TC) Victor (1997) using the Weather Research and Forecasting Model. TC Victor originated in the South China Sea and made landfall over the Greater Bay Area (GBA) megacity. The storm was characterized by slow movement, a weakly organized structure, and a small size. Three parallel experiments were conducted in the following setups: “Nourban,” where urban areas in the GBA were replaced by croplands, “AH0” (“AH300”), in which the diurnal maximum AH was set to 0 (300 W/m2) in urban locations. The urbanization effect during the landfall period results in a notable reduction in both the Power Dissipation Index and Integrated Kinetic Energy of the storm. A Lagrangian particle dispersion model further demonstrates that from 33 to 17 hr prelandfall, the entrainment of AH‐affected warm airflow into the TC's circulation leads to a decrease in both the convective available potential energy and surface latent heat flux in the western quadrant of the TC, thus weakening the cyclone's intensity. Furthermore, from 12 hr prelandfall to 8 hr postlandfall, there is an intense influx of AH‐affected airflow into the TC's primary circulation, resulting in a decrease in relative humidity and a stronger asymmetrical structure, declining the TC intensity. Concurrently, urban surface roughness contributes to a decrease in postlandfall storm intensity through frictional energy dissipation. This study underscores the critical role of AH and urban roughness in modulating TC intensity for storms with specific characteristics, emphasizing the need for deeper insights into urban‐TC dynamics.