Solar radiation modeling from satellite imagery

Abstract

Satellites have been observing the earth-atmosphere system and delivering data since the 1960s. They constitute a crucial tool for observing, measuring, and understanding meteorological phenomena and radiative transfer budgets. Satellite observations are usually incorporated into numerical weather predictions (NWP) models, via data assimilation algorithms, to produce the best estimate of the atmospheric state and to improve weather forecasting. In the field of solar radiation, satellite imagery provides effective information since onboard sensors actually measure the incoming radiance form the earth-atmosphere system. The radiance received by satellites is related to solar radiation incident at the earth’s surface since it results from the different interactions of the sun’s radiation with the earth-atmosphere system—scattering, absorption, and reflection. Therefore, it is reasonable to design methods and algorithms to infer surface solar irradiance from the radiance received by the satellites’ onboard instruments. The first algorithms were developed in the 1980s. They have significantly evolved since and have reached a high degree of maturity and accuracy thanks to continuous developments and improvements both in the methods and in onboard radiometric instrumentations (in particular, spectral and geographical resolution). Every solar energy project requires an accurate knowledge of the local solar resource. Although the number and geographical density of ground-based solar radiation sensors are continuously increasing, they can only supply the needed solar resource information in a handful of locations. In consequence, most solar energy projects rely on solar irradiance time series simulated from satellite imagery. Satellite-derived information can be processed into many forms useful to the solar community, including solar radiation maps, typical meteorological (or representative) years, long-term characterization, and solar plant performance modeling. This chapter presents a state-of-the-art review of the modeling of surface solar irradiance from satellite images.