MODELING TOPOGRAPHIC SOLAR-RADIATION USING GOES DATA

In this paper the authors present an algorithm that combines solar rad iation fields derived from Geostationary Operational Environmental Sat ellite (GOES) observations with digital elevation data to produce topo graphically varying insolation fields at fine grid spacing. Cloud-modu lated irradiances are obtained using hourly 8-km resolution GOES obser vations. These irradiances are then spatially integrated to the grid s pacing of the digital elevation data. The integration accounts for unc ertainties in satellite navigation, the limited sensor resolution rela tive to the hemispheric field of view of a terrain element, and the mi smatch between the instantaneous fluxes estimated by GOES observations and the time-integrated quantities typically used in distributed mode ling, such as hourly fluxes. The integrated fields are partitioned int o direct and diffuse components and then adjusted for the effects of e levation. Lastly, other topographic effects, such as slope orientation , shadowing, sky obstruction, and terrain reflectance are modeled usin g fields derived from the digital elevation data. The final product is a map of solar radiation that marries coarse-scale variability in ins olation caused by clouds with the finescale variability caused by topo graphy. The authors demonstrate the technique for a portion of the Roc ky Mountains, using a 90-m digital terrain model covering over 1 degre es x 1 degrees of latitude and longitude. Lastly, assumptions, limitat ions, and sources of error in data and algorithms are discussed.