Quality Assessment Based Upon Comparison with Models
Many models based on the physics of radiation transfer through the clear atmosphere have been developed (Lacis and Hansen 1974; Atwater and Ball 1978; Hoyt 1978; Bird and Hulstrom 1981a, 1981b; Davies, McKay 1982; Gueymard 1993, 2008). These models can be compared with clear-sky measured data to determine if measured data deviate significantly from “expected” data.
Satellite-based remote sensors and the development of algorithms for estimating the solar flux at the surface has also lead to the possibility of using satellite-based estimates to evaluate the performance of ground-based sensors (Perez et al. 1997, 2002; Myers 2005). An example of a web-based means of evaluating ground-based measurements with respect to estimates derived from satellite data has been described (Geiger et al. 2002).
Of course, in all cases, model inputs or flux estimation algorithms have to be relatively accurate, and there must still be tolerances on measured data to account for possible instrumentation bias errors, as well as an idea of the additional sources of uncertainty in the models and algorithms themselves (Gueymard and Myers 2007).