Conversion of 400-1100 nm vegetation albedo measurements into total shortwave broadband albedo using a canopy radiative transfer model

The surface albedo was measured during the ReSeDA experiment over several fields with two different devices: Kipp thermopiles and Skye silicon photopiles. The comparison of different datasets shows a systematic bias between the measurements performed by the two devices: the albedos measured by the Skye instruments are overestimated compared to the Kipp ones. This difference is due to a specific problem with the Skye radiometers, which were designed for incident solar radiation measurements, whereas they were used to measure reflected crop radiation. Moreover, the Skye filter function uses a bandwidth corresponding to the 400-1100 nm region only, and not the whole spectra. The SAIL model was used to correct the Skye measurements by simulating the response of the instrument and the true albedo on each experimental field. After this correction, the albedos actually show a good agreement between the data acquired by the two devices.