Validation of the MCD43A3 Collection 6 and GLASS V04 Snow-Free Albedo Products Over Rugged Terrain

A comprehensive assessment of satellite-derived albedo products is undeniably essential for better use consideration and the further refinement of the retrieval algorithm. Although satellite albedo products have been extensively validated over spatially homogeneous areas, it remains a challenge to validate them over rugged terrain. Consequently, the accuracy of satellite albedo products over rugged terrain is still unknown. This study for the first time systematically evaluated two widely used satellite albedo products (i.e., MCD43A3 V006 and Global Land Surface Satellite (GLASS) V04 albedo) over mountainous areas with a mountain radiation transfer (MRT) coupled multiscale validation strategy. Fine-scale albedo was first generated with a root-mean-square error (RMSE) smaller than 0.0317. Then, they were upscaled to the coarse pixel and as the reference data for validation. The validation results indicated that the accuracy of the two products tends to decrease with the increase of means slopes. The RMSE and relative RMSE (RMSE
$_{R}$
) of full retrieval MCD43A3 C6 black-sky albedo (BSA) and white-sky albedo (WSA) over abrupt slopes (mean slope > 10°) increase to 0.0432% and 31.87% and to 0.0436% and 32.21%, respectively. The RMSE and RMSE
$_{R}$
of high-quality GLASS V04 were 0.0452% and 33.71% of BSA and 0.0458% and 33.92% of WSA, respectively, over abrupt slopes. In particular, if the backup retrievals were included over the abrupt slopes, the RMSE and RMSE
$_{R}$
of MCD43A3 C6 can reach 0.0600% and 36.92% for BSA and 0.0613% and 37.67% for WSA, respectively, and those of GLASS V04 can reach 0.0567% and 36.28% for BSA and 0.0540% and 35.72%, respectively.