This report deals with estimates of hourly averages of incoming shortwave (solar) radiation and net radiation from standard meteorological observations.
It is shown that incoming shortwave radiation can be estimated relatively accurate from solar elevation and total cloud cover only. Furthermore, from incoming shortwave radiation, albedo, total cloud cover and screentemperature the net radiation can be estimated by day, with a fair accuracy. In the night the net radiation can be estimated, but not very accurately, from the observed windspeed and total cloud cover.
A.A.M. Holtslag and A.P. van Ulden . Estimates of incoming shortwave radiation and net radiation from standard meteorological data
KNMI number: WR-80-06, Year: 1980, Pages: 24