986 / 2024-09-19 23:54:48

Warming and wetting induced by urbanization and anthropogenic heat in summer over the Pearl River Delta

urbanization,anthro,warming,precipitation,urban

Session 24 - Estuaries and coastal environments stress - Observations and modelling

Urbanization induced extreme precipitation and related hazards, such as urban flooding, have been increasingly common in the Pearl River Delta (PRD). This study investigates the impacts of urbanization and anthropogenic heat (AH) on air temperature and precipitation in the PRD region during the summer. 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 regional climate by increasing the air temperature and surface wind and by altering planetary boundary layer (PBL) height and precipitation in the urban area. Urbanization alters the surface energy balance, increases sensible heat flux and reducing latent heat flux, thereby intensifies the urban heat island (UHI) effect. The inclusion of AH further amplifies these effects, leading to even higher temperatures and strong precipitation. The physical processes analysis indicates that alternation of PBL process is the key driver for the change, which leads to change of horizonal and vertical motion and redistribution of heat and moisture.  Urbanization enhances vertical heat flux divergence within the PBL, and AH intensifies this effect, significantly contributing to temperature rises. On the other hand, the increased rainfall is primarily driven by intensified moisture flux convergence due to urbanization. AH further amplifies moisture advection and wind convergence, resulting in more pronounced precipitation over urban area. These findings highlight the significant impact of urbanization and AH on the regional climate of the PRD, underscoring the need for better representation of urban processes in climate models to reflect regional change.