The efficacy of roof mitigation strategies for urban heat island in various background climate

Urban heat island (UHI) is a significant anthropogenic climate impact in cities, with construction and human activities altering the radiative and thermodynamic properties of urban surfaces, leading to higher temperatures relative to rural areas. Mitigation strategies such as green roofs (GR) and cool roofs (CR) have been implemented to counteract UHI, reducing adverse effects like exacerbated heat waves and increased cooling energy demand. However, limited research has addressed the influence of background climate on the efficacy of these mitigation measures. Given that background climate factors—such as regional temperature, humidity, and precipitation—can significantly impact processes like evapotranspiration and albedo, it is crucial to assess how these factors interact with mitigation strategies.

This study uses the Weather Research and Forecasting (WRF) model to evaluate the mitigation effects of CR and GR across six populous mega-cities in China, which represent a range of background climates from temperate semi-arid to subtropical humid. To accurately simulate urban heat environments, various urban parameterization schemes (e.g., LCZ, UCP) and urban climate models (e.g., SLUCM, BEP, BEM+BEP) were tested, and the best combination was selected for simulation. Sensitivity tests were conducted across multiple scenarios, ranging from practical to idealized conditions, to assess the impact of background climate on mitigation effectiveness. The results indicate that background climate and regional weather patterns significantly influence the success of UHI mitigation strategies. These findings offer valuable insights for urban planning and the design of context-specific UHI mitigation measures.