Mapping Brightness Temperature and Urban Heat Islands at a City Scale in Egypt Using 3D Radiative Transfer Modeling and UAV Imagery

Abstract

Rapid urbanization, a hot climate, and poor urban planning have intensified the Urban Heat Island (UHI) effect in Egyptian cities. However, remote-sensing-based mapping of UHIs at a micro-scale for mitigation purposes remains challenging. Reasons include the cost of high-resolution satellite imagery and legal restrictions on Unmanned Aerial Vehicles (UAVs) usage. To address this dilemma, this study introduced a framework for UHI spatial distribution mapping at a micro-scale for Aga City, Egypt, by simulating Brightness Temperature (BT) using the Discrete Anisotropic Radiative Transfer (DART) model. Optical and thermal UAV imagery—used here for the first time for urban 3D modeling in Egypt—were utilized for model parameterization. Multiple GIS-based approaches for reconstructing an accurate 3D model of the city were examined. The framework accurately simulated the BT spatial distribution, showing strong agreement with observations derived from Landsat 9 thermal data. UHI spatial distribution was generated, revealing moderate to severe hot spots across the city. UHI mitigation scenarios were tested by carrying out additional simulations under prescribed surface temperature assumptions. Results showed that white asphalt and green roofing reduced mean BT by 4 K and 5 K, respectively, making them promising solutions for UHI mitigation in dense Egyptian cities.