Urban radiation balance of two coastal cities in a hot and dry environment

Four Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) satellite scenes of Dubai and Abu Dhabi with channels from the visible-near infrared (VNIR) to the thermal infrared (TIR) were analysed to show variations in surface temperature, albedo, emissivity and net radiation in different urban and rural classes. For a better understanding of the spatial coherences of surface properties a land use classification was derived. The different classes were then spatially and temporally compared. The investigations show in the daytime a distinct surface cool island for Dubai and surface cool areas at Abu Dhabi city and its surrounding mangrove areas. Net radiation is mainly controlled by the albedo. The albedo in urban areas is lower than in their surrounding desert environments, therefore the net radiation is higher in the urban areas. The surface temperatures behave contrary to the net radiation and are higher in land use classes, where water is available.