Preprocessing of Airborne Pyranometer Data

Eppley pyranometers are employed to measure the up- and downwelling short wavelength radiation fluxes in the atmosphere. The quality of the data used to investigate the radiation budget and extinction of solar irradiance depends strongly on the calibration and correction applied to the radiation data, accounting for (1) cosine response of the instruments, (2) ambient temperature effects, (3) leveling of the radiometers, and (4) aircraft maneuvers during the observations. This report makes suggestions about how the quality of the radiation data can be enhanced by a more accurate calibration procedure and correction scheme. By considering the recommendations, data from the upward facing pyranometer can be improved by about 20% under clear sky conditions.