| Abstract: | When diffuse radiation is measured with a pyranometer and the access of beam radiation to the measuring instrument is obstructed by using a shadow band, a band correction has to be made to obtain the correct result of measurement. The magnitude of the correction depends on the size and location of the shadow band and the sky radiance distribution. A two-component sky radiance model can be utilized when making the band correction. Measurements indicate that the band correction based on the isotropic approximation of the radiance distribution leads to an underestimation of the diffuse irradiation. By using the radiance model, this systematic error can be eliminated. In measurements of high quality, the effect of the radiation reflected from the inside of the band to the pyranometer should also be taken into account. |
