## 5 Albedo Inversion and Analysis
### Results Analysis and Verification  
Due to the lack of field measurement data, the MODIS albedo product MCD43A3 (Albedo 16-Day L3 Global 500 m) was used to evaluate the results of albedo retrieval in this study. It presents the inversion results of the white-sky albedo and the black-sky albedo [35]. Figure 16 shows the albedo product obtained by weighting the sky diffusely scattered light scale factor \(S\) according to the black-sky and white-sky albedo in MCD43A3. In addition, the data have undergone spatial scale change and spectral correction; see Section 3.2 for the data processing method. The distribution ranges of the surface albedo of the Hefei area on these four days are 0.0412\(\sim\)0.1863, 0.0302\(\sim\)0.1978, 0.0169\(\sim\)0.1693, and 0.0420\(\sim\)0.2071. Figure 17 shows the comparison error between the FY-2G albedo inversion results and the MODIS albedo product. The missing blank pixels in the figure are because the MODIS albedo product has no effective value in the pixel. The average errors of each scene image are \(-\)0.0257, \(-\)0.0073, 0.0133, and \(-\)0.0294. The root mean square errors (RMSEs) are 0.0375, 0.0235, 0.0275, and 0.0436. At the same time, the pixels with high-quality assurance (QA) in MODIS albedo products were selected for comparison. The MODIS albedo products had 190, 1, 270, and 109 high-QA pixels in Hefei during the four days. Figure 18 shows the comparison scatter plot between the FY-2G albedo inversion results and the high-QA MODIS albedo products. The average root mean square errors are 0.0329, 0.0043, 0.0192, and 0.0406, and the absolute errors are \(-\)0.0240, \(-\)0.0043, 0.0138, and \(-\)0.0260. The inversion results are in good agreement with the high-QA MODIS albedo products. The inversion results on the 24 th, 107 th, and 302 nd days are generally smaller than those of MODIS, and the inversion results on the 228 th day are generally higher than those of MODIS.  
Figure 14: LOSS value of HuberLoss regression fitting.  
Figure 15: The proportion of each class in the BRDF archetype during the albedo inversion of the Hefei area.  
At the same time, the albedo inversion results of Huber loss regression fitting and least squares regression fitting are compared. Figure 19 is a scatter diagram of the albedo inversion results obtained by using these two fitting methods. In the figure, the abscissa is the albedo fitted by the least square method, and the ordinate is the albedo obtained by the Huber loss method. It can be seen from the comparison results that the surface albedo results obtained by the two regression analysis methods are relatively consistent. The Pearson's coefficient of the two results is 0.96829, and the R-square is 0.93736. Considering the relatively small sample size, although the comparison results show that there is little difference between the two methods, the amount of fitting regression data is sufficient on the premise that it is based on geostationary satellite data, but the Huber loss regression method has certain advantages in theory. The land surface albedo inversion results obtained in this study have higher accuracy and better method stability.  
Figure 16: Surface albedo in the MODIS albedo product MCD43A3 on days 24, 107, 228, and 302 in 2019.  
Figure 17: Comparison error between FY-2G albedo inversion results and MODIS albedo products.  
Figure 18: Comparison error between FY-2G albedo inversion results and MODIS albedo products with high QA.