On the calibration of the radiometer for longwave radiation. II - The case of pyrgeometer

In the calibration device proposed for pyrgeometers intended for measuring the hemispherical upward and downward radiation fluxes, the radiation source is a water surface with a large number of tiny water jets. The influence of a wind field on the sensitivity (accuracy) of some conventional pyrgeometers is studied, showing that the sensitivity decreases in proportion to the wind speed, and that the decrease is greater for ventilation-type (Gier and Dunkle type) pyrgeometers. The measurement error of ventilation-type, Funk-type, and Eko-type pyrgeometers is assessed.