ABSTRACT
Modeling solar radiation under all sky conditions is considerably more difficult and uncertain than modeling clear sky solar radiation. The physics of cloud transmittance and the extremely wide variety of spatial distributions of clouds are the main contributors to these difficulties. There are some truly physically induced correlations between solar radiation values and meteorological variables, particularly air temperature, changing atmospheric constituents, and observed cloud cover. Another popular correlation is that between maximum theoretically available hours of sunshine and actual hours of sunshine. One of the most famous and most exercised models for estimating solar radiation is based on the duration of actual sunshine versus total possible sunshine. The model was developed by Angstrom and is referred to as the Angstrom sunshine model. The International Satellite Cloud Climatology Program coordinates and collates data from international cloud-observing satellite programs. The archived and future data collected by this program may serve as a good resource for all future sky solar radiation model development.
