HI-85-05-3 -- Synthetic Solar Radiation Statistics on Cloudy and Sunny Days PDF

A methodology is discussed to obtain global solar radiation estimates and temperature from cloud, visibility, data. Estimates are given for the absorption by water vapor and CO₂. The data are further stratified by cloud groups. Results are compared with data derived from the SOLMET network and Huntsville, Alabama.

For Huntsville, synthetic monthly means stay within 3% of observed data. Our model values resemble data of the direct solar radiation in the winter months and global radiation during summer for three selected urban areas. While CO₂ contributes only 1% to the absorption, water vapor absorption stays around 25% and the cloud effect reduces radiation by 10% to 20%. It appears that on overcast days with high ceiling, 50% of the solar radiation still would be available; on days with 5 to 7 eighths cloud cover, even 75% to 85%. Only on overcast days with low clouds is the amount reduced on the average to 25% to 40%.

Units: SI