A simulation of topographic solar radiative forcing over a mountainous region using geostationary satellite data

The radiative forcing effects of topography and clouds were examined for a mountainous region during the rainy season to further our understanding of the relative roles of each in modulating incoming solar energy at the Earth´s surface. Solar radiation fields derived from hourly, 8 km GOES observations were used to drive a topographic solar radiation model at 60 m resolution during August 1988, for the Rio Grande River basin in Colorado. Monthly, basinwide mean solar radiative forcing as a percentage of average, clear-sky insolation was -37.3% for clouds and +10.2% for topography. The overall positive monthly topographic forcing (+10.2%) resulted from positive elevation effects (+18.6%); these outweighed the negative forcings (-8.4%) caused by terrain. These results suggested that topography must be considered for clear, cloudy, and partly cloudy conditions in mountainous regions, even at coarse temporal and spatial scales