Open Access

Daniel Vivor

• Rapid urbanization in tropical cities is intensifying the Urban Heat Island (UHI) effect. The results of which are extreme thermal discomfort, high building-energy demands, and public health risks. Accra, the capital of Ghana, exemplifies these challenges. Over the past decades the region has seen the use of impervious materials in construction projects, and a decline in vegetation cover. This is contributing to rising land surface and air temperatures. This study evaluates the potential of green roofs and tree planting to mitigate UHI effects and improve thermal comfort in Accra’s Central Business District. The evaluation process combines remote sensing analysis in Google Earth Engine with ENVI‑met microclimate simulations. Green roofs, tree planting and a combined mitigation strategy scenarios are modelled to assess changes in three key indicators: outdoor air temperature at pedestrian level, Physiological Equivalent Temperature (PET)/ Thermal comfort, and roof surface temperature. Given the limited spatial extent Envi-met can simulate in a single run, R‑based spatial interpolation is used to extend results across the study area. Results show that tree planting only produced the most improvements in thermal comfort. Green roofs significantly reduced roof surface temperatures, with maximum reductions exceeding 30 °C compared to conventional rooftops. Green roofs also influence the ambient air temperature, though more localized. The combined intervention shows complementary benefits, simultaneously improving thermal comfort and potentially reducing building-energy demands. Two different tree species are also evaluated to test how species choice influences air temperature and thermal comfort. Neem (Azadirachta indica) outperforms African Mahogany (Khaya senegalensis) in reducing PET, but both perform similarly in impacts on air temperature. It should also be mentioned that these UHI mitigation strategies produced negative effects i.e. increasing air temperature or thermal comfort at certain periods of time. The findings highlight the benefits and in some cases the downsides of integrating vegetation‑based strategies into Accra’s urban planning framework. By quantifying the microclimatic effects of green roofs and trees, this research provides evidence‑based guidance for policymakers and urban planners to reduce heat stress and promote sustainable urban development.