This project supports the Solar America Initiative by: (1) meeting increasing demands for expertise in and products on solar radiation data and models--production and distribution of reliable, accurate domestic and international solar resource data, benchmarking and cross-comparison of solar irradiance models; and coordination with the international community (IEA/SHC Task 36, WMO); (2) reducing data uncertainties and increasing temporal and spatial data resolutions; (3) developing and testing short term solar resource forecasts; (4) evaluating methods for producing long term data sets from short term observations; and (5) conducting measurement activities at selected sites