Warming and wetting induced by urbanization and anthropogenic heat over a fast-developing large river delta

Abstract This study investigates the impacts of urbanization and anthropogenic heat (AH) on air temperature and precipitation in the Pearl River Delta subject to rapid socioeconomic development. Using the Weather Research and Forecasting (WRF) model, coupled with a single-layer urban canopy model, three scenarios (non-urban, urban without AH, and urban with AH) were analyzed. Results reveal that urbanization significantly alters the regional climate, increasing air temperature, land-sea circulation, planetary boundary layer (PBL) height and precipitation in the urban areas. Urbanization alters the surface heat balance, increasing sensible heat flux and reducing latent heat flux, while AH further amplifies the urban heat island (UHI) effect, leading to higher temperature and increased precipitation. Both urbanization and AH enhance vertical motion, redistributing moisture to higher atmospheric levels and increasing precipitation. The air temperature changes are driven primarily by the PBL process and temperature advection. Urbanization enhances the vertical divergence of turbulent heat flux within the PBL, and AH intensifies this effect, significantly contributing to rises in temperature. Moisture budget analysis highlights that the increased rainfall is driven primarily by intensified moisture flux convergence resulting from urbanization, with dynamic effect (wind convergence) playing a dominant role and thermodynamic effect (moisture advection) playing a secondary role. AH further amplifies both the moisture advection and wind convergence, intensifying urban precipitation. These findings emphasize the significant impact of urbanization and AH on the regional climate, underscoring the need for better representation of urban processes in climate models to address the effects of rapid urban expansion.