The interaction between clouds and shortwave (SW) radiation affects the SW radiation incident on the surface, modulating the surface energy budget and consequently the atmospheric energy budget. Quantifying the effect of clouds on SW radiation, the SW cloud effect, requires comparing measured SW irradiances with expected clear sky SW irradiances. An earlier algorithm that estimates clear sky SW irradiances using only one-minute averages of measured SW irradiances is modified to allow use of up to 15-minute averages of measured SW irradiance data.

The modified algorithm and resulting interpolated clear sky SW irradiances are used to compile a database of SW cloud effects for surface-based stations located in different geographic and climatic locations. A summary of the SW cloud effects and discussion of them in terms of the local climate regimes will be presented.