Parameterization of net radiation in an arid city of northwestern Mexico

During the process of urbanization, different surface properties significantly alter the radiation balance. This paper attempts to quantify this balance over different surface types in an arid city of northwest Mexico over several days in August 2011. The albedo of each surface type, as well as local atmospheric properties such as the atmospheric clearness index (K-0) and atmospheric emissivity (epsilon(atm)), were estimated. The surfaces on which measurements were performed were asphalt, concrete, polystyrene painted with white elastomeric paint (PWEP), clay, and grass. It was found that, for a 24-h cycle of measurement, the highest average value of net radiation was for asphalt (146.1 Wm(-2)), and the lowest average value was for PWEP (33.6 Wm(-2)). Estimates of albedo values vary depending on the surface, whereas K-0 and epsilon(atm) are dependent on prevailing atmospheric conditions. From these measurements, preliminary statistical models of net radiation as a function of incoming solar radiation and net shortwave radiation were proposed. For each model, the coefficients of determination were higher than 0.97. We discuss the likely implications of the results found for the urban planning of the city.