The projected effects of urbanization and climate change on urban Heat Island and thermal comfort over the Tehran metropolitan

Rapid urbanization and changes in land-use patterns have intensified global environmental challenges in megacities. As cities confront the dual pressures of urbanization and climate change, understanding their individual and combined impacts on the thermal environment and urban resilience remains a critical research priority. This study employs the Weather Research and Forecasting (WRF) model coupled with the single-layer Urban Canopy Model (UCM) to investigate the localized effects of urbanization and climate change on Tehran during July, focusing on the present (2019–2023) and mid-term future (2050–2054) under SSP1–2.6, SSP2–4.5, and SSP5–8.5 scenarios. The results reveal that urbanization and climate change interact to exacerbate warming and reduce wind speeds in all selected scenarios. Tehran's urban area warms by 3.43 ± 0.48 °C until 2050–2054 under the SSP5–8.5 scenario, with 0.46 ± 0.31 °C attributed to urbanization, and 2.93 ± 0.43 °C to climate change. In urban areas, wind speed decreases by −1.63 ± 0.19 m/s, primarily due to climate change (84.66 %), reducing urban ventilation. Future urbanization, however, increases 10-m wind speed by 0.09 ± 0.02 m/s daily and 0.20 ± 0.02 m/s during daytime. Thermal comfort variations are assessed using HI, THI, and ETI indices, which show increases of 4.46 ± 0.28 °C, 2.57 ± 0.25 °C, and 2.84 ± 0.27 °C, driven mainly by global warming (73–87 %). This study also evaluates the effectiveness of cool roofs in mitigating adverse microclimatic impacts of future urbanization and climate change. The results reveal that although cool roof helps mitigate the effects of urbanization and climate change on temperature rise and thermal comfort by up to 4.37 % and 15 %, respectively, it also exacerbates the reduction in wind speed by 8.58 %, hindering pollutant dispersion. This study shows the need to integrate urbanization and climate change impacts into sustainable urban planning, offering valuable insights for targeted adaptation and mitigation strategies.