## 4 Results
### Direct Validation with In Situ Datasets
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Bias (m\({}^{3}\)/m\({}^{3}\))**} & \multicolumn{2}{c}{**R**} & \multicolumn{2}{c}{**RMSE (m\({}^{3}\)/m\({}^{3}\))**} & \multicolumn{2}{c}{**ubRMSE (m\({}^{3}\)/m\({}^{3}\))**} \\ \cline{3-10}  & & **OWCM** & **GM** & **OWCM** & **GM** & **OWCM** & **GMs** & **OWCM** & **GMs** \\ \hline \multirow{4}{*}{Naqu-P3} & ER & **0.0176** & 0.0331 & **0.9692** & 0.8225 & **0.0354** & 0.0695 & **0.0307** & 0.0613 \\  & ATA & **0.0108** & 0.0289 & **0.9546** & 0.8374 & **0.0370** & 0.0689 & **0.0354** & 0.0627 \\  & RF & **0.0106** & 0.0798 & **0.9519** & 0.4368 & **0.0385** & 0.1175 & **0.0371** & 0.0865 \\  & NN & **-0.0153** & -0.0174 & **0.9587** & 0.6723 & **0.0460** & 0.0792 & **0.0435** & 0.0775 \\ \hline \multirow{4}{*}{Naqu-MS494} & ER & **-0.0187** & -0.0764 & **0.7122** & 0.7007 & **0.0747** & 0.1283 & **0.0725** & 0.1034 \\  & ATA & **-0.0255** & -0.0683 & **0.7412** & 0.4086 & **0.0730** & 0.1192 & **0.0686** & 0.0980 \\  & RF & **-0.0247** & -0.0664 & **0.7204** & 0.2031 & **0.0698** & 0.1376 & **0.0655** & 0.1209 \\  & NN & **-0.0759** & -0.1055 & **0.6908** & 0.3898 & **0.1172** & 0.1497 & **0.0895** & 0.1065 \\ \hline \multirow{4}{*}{Naqu-MS3518} & ER & **0.0122** & 0.0355 & **0.9633** & 0.8410 & **0.0378** & 0.0769 & **0.0359** & 0.0684 \\  & ATA & **0.0029** & 0.0204 & **0.9621** & 0.8591 & **0.0383** & 0.0724 & **0.0383** & 0.0697 \\  & RF & **0.0110** & 0.0431 & **0.9703** & 0.3298 & **0.0416** & 0.1059 & **0.0402** & 0.0970 \\  & NN & \(-0.0211\) & **-0.0208** & **0.9645** & 0.8037 & **0.0452** & 0.0833 & **0.0401** & 0.0809 \\ \hline \multirow{4}{*}{Naqu-NST03} & ER & **-0.0345** & -0.0911 & **0.7445** & 0.3446 & **0.0494** & 0.1163 & **0.0355** & 0.0726 \\  & ATA & **-0.0424** & -0.0980 & **0.8922** & 0.1053 & **0.0496** & 0.1134 & **0.0258** & 0.0572 \\  & RF & **-0.0768** & -0.1067 & **0.7079** & 0.2487 & **0.0858** & 0.1217 & **0.0377** & 0.0587 \\  & NN & **-0.0934** & -0.1392 & **0.8038** & 0.1798 & **0.0987** & 0.1500 & **0.0321** & 0.0560 \\ \hline \multirow{4}{*}{Naqu-NST09} & ER & **0.0083** & 0.0346 & **0.8713** & 0.5545 & **0.0273** & 0.0583 & **0.0261** & 0.0470 \\  & ATA & **-0.0048** & **0.0076** & **0.8890** & 0.5340 & **0.0260** & 0.0458 & **0.0247** & 0.0453 \\ \cline{1-1}  & RF & **-0.0010** & 0.0068 & **0.7627** & 0.4211 & **0.0341** & 0.0493 & **0.0342** & 0.0490 \\ \cline{1-1}  & NN & **-0.0036** & -0.0352 & **0.7937** & 0.1686 & **0.0335** & 0.0665 & **0.0335** & 0.0566 \\ \hline \multirow{4}{*}{Ngavi-SQ06} & ER & **-0.0340** & -0.0853 & **0.8122** & 0.0242 & **0.0398** & 0.0922 & **0.0208** & 0.0349 \\ \cline{1-1}  & ATA & **-0.0418** & -0.0894 & **0.7748** & 0.1711 & **0.0472** & 0.0959 & **0.0219** & 0.0348 \\ \cline{1-1}  & RF & **-0.0541** & -0.1304 & **0.7879** & 0.1463 & **0.0584** & 0.1354 & **0.0220** & 0.0366 \\ \cline{1-1}  & NN & **-0.0425** & -0.0958 & **0.7717** & 0.0915 & **0.0481** & 0.1025 & **0.0227** & 0.0365 \\ \hline \multirow{4}{*}{Ngavi-SQ14} & ER & **0.0041** & 0.0565 & **0.6734** & 0.1124 & **0.0232** & 0.0644 & **0.0229** & 0.0309 \\ \cline{1-1}  & ATA & 0.0074 & **0.0358** & **0.8455** & 0.2705 & **0.0180** & 0.0466 & **0.0165** & 0.0300 \\ \cline{1-1}  & RF & **-0.0025** & 0.0491 & **0.7261** & 0.0054 & **0.0217** & 0.0585 & **0.0216** & 0.0319 \\ \cline{1-1}  & NN & **-0.0141** & 0.0455 & **0.7850** & 0.0470 & **0.0237** & 0.0578 & **0.0191** & 0.0358 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Statistical metrics of GM-/OWCM-derived fine-RES SM datasets based on comparisons with in situ SM measurements. The superior metric within each pair of corresponding GM and OWCM products is indicated by bold type. OWCMs separates high- and low-frequency SM features in a way that better captures the relationship between SM and various land-surface attributes. Second, in situ measurement sites with lower spatial heterogeneity demonstrate better representativeness of the overall grid cell and, therefore, minimize error associated with point-to-grid-cell upscaling.