Abstract
This study assessed accuracies of MCD43A3, Global Land-Surface Satellite (GLASS) and forthcoming Multi-source Data Synergized Quantitative Remote Sensing Production system (MuSyQ) albedos using ground observations and Huan Jing (HJ) data over the Heihe River Basin. MCD43A3 and MuSyQ albedos show similar high accuracies with identical root mean square errors (RMSE). Nevertheless, MuSyQ albedo is better correlated with ground measurements when sufficient valid observations are available or snow-free. The opposite happens when less than seven valid observations are available. GLASS albedo presents a larger RMSE than MCD43A3 and MuSyQ albedos in comparison with ground measurements. Over surfaces with smaller seasonal variations, MCD43A3 and MuSyQ albedos show smaller RMSEs than GLASS albedo in comparison with HJ albedo. However, for surfaces with larger temporal variations, both RMSEs and R2 of GLASS albedo are comparable with MCD43A3 and MuSyQ. Generally, MCD43A3 and MuSyQ albedos featured the same RMSEs of 0.034 and similar R2 (0.920 and 0.903, respectively), which are better than GLASS albedo (RMSE = 0.043, R2 = 0.787). However, when it comes to comparison with aggregated HJ albedo, MuSyQ and GLASS albedos are with lower RMSEs of 0.027 and 0.032 and higher R2 of 0.900 and 0.898 respectively than MCD43A3 (RMSE = 0.038, R2 = 0.836). Despite the limited geographic region of the study area, they still provide an important insight into the accuracies of three albedo products.
Highlights
Land-surface albedo is defined as the ratio of the upward and downward radiation at a surface [1]
It is noticeable that the Global Land-Surface Satellite (GLASS) albedo shows larger root mean square errors (RMSE) than those of MuSyQ albedo and MCD43A3 over most of these sites (Figure 4a)
It can be found that the magnitudes of the Bias of GLASS albedo are always larger than those of MuSyQ albedo and MCD43A3 over these sites (Figure 5a)
Summary
Land-surface albedo is defined as the ratio of the upward and downward radiation at a surface [1]. Decreased surface albedo promotes the absorption of solar radiation by land surface and contributes to global warming as well as snow and ice melting, which, in turn, leads to decreased surface reflection and increased warming effects. The positive feedback of surface albedo on climate directly affects surface energy budget and the earth’s radiation balance [2,3,4,5]. Satellite remote sensing provides a practical way to efficiently and frequently map surface albedo regionally and globally [8]. The satellite-derived albedo is not a directly observed variable but is indirectly calculated from the satellite-observed surface reflectance or radiance using albedo algorithms. Albedo is associated with the land-surface reflectance by integrating over the angular and spectral domains, and depends on the land-surface bidirectional reflectance distribution function (BRDF), which describes the anisotropic reflective properties of land surfaces [9]
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