Comparison of seasonal and spatial variations of albedos from Moderate-Resolution Imaging Spectroradiometer (MODIS) and Common Land Model

This paper compares seasonal and spatial variations of Moderate Resolution Imaging Spectroradiometer (MODIS) albedos with those from the Common Land Model (CLM) by land cover type. MODIS albedo data in the year 2001 were used to determine seasonal, spatial, and land cover dependence at 1 km resolution and to investigate the biases in CLM. Albedo dependence on vegetation type is smaller than that on snow and soil. Snow causes the largest temporal and spatial variations, especially in the visible band (0.3-0.7 μm). CLM has visible albedos that are lower by up to 0.4-0.5 in winter over northern high latitudes but are globally higher by 0.02-0.04 in summer over most vegetation, mainly due to its overestimated leaf and stem area index in winter and slightly higher prescribed canopy albedos in summer, respectively. MODIS and CLM differ considerably in soil albedo over desert and semidesert regions, especially in the near-infrared band (0.7-5.0 μm), with the largest low bias of about 0.1 in the Sahara. Adjustments of the prescribed albedos in CLM based on MODIS observations could reduce such biases. Therefore the model should better represent leaf and stem area index, vegetation albedo in the presence of snow, and soil albedo.