Influence of anthropogenic water dissipation on urban heat island – a case study of Beijing

Abstract

In the process of rapid urbanization, anthropogenic water use activities (such as indoor building water use, road sprinkling, and vegetation irrigation, etc.) have become an important part of urban water cycle, and the water vapor dissipation generated by evaporation and transpiration has a significant impact on urban energy balance and local climate. However, the current mainstream urban climate models generally lack a detailed description of urban anthropogenic water dissipation process, which limits their ability to simulate urban heat island effect and hydrological process. This study constructed a calculation model for urban anthropogenic water dissipation, incorporated moisture fluxes from anthropogenic water consumption activities into the UCM and coupled it with the WRF model for simulation. Taking typical periods of summer and winter in Beijing as examples, the influence of anthropogenic water dissipation on the UHI was simulated and analyzed. The results show that anthropogenic water dissipation significantly increases the latent heat flux (LH) and specific humidity in urban areas. In summer, the LH in urban areas increases by about 30 W/m², and the 2 m average temperature decreases by about 0.7 ℃, thus effectively reducing the intensity of the UHI. Although the anthropogenic water dissipation decreases in winter, it still has a positive effect on maintaining a relatively high specific humidity. The specific humidity in urban regions increases by about 0.12 g/kg. The simulation results are verified by observational data with high accuracy, emphasizing the necessity of incorporating anthropogenic water dissipation processes in urban climate model.