## 4 Results
### Development of the Global MODIS Time-Share Two-Stage CI Product
#### 4.2.3 Accuracy Evaluation for the MODIS Time-Share Two-Stage CI Product  
Figure 6 shows the accuracy evaluation results when the time-share two-stage CIs are compared with the field-measured CIs. A total of 95 datasets were involved in the evaluation, and the time-share two-stage CIs and the field-measured CIs were roughly in agreement (RMSE = 0.06, bias = 0.01). Among them, nine data points were overestimated by more than 0.1, and six data points were underestimated by more than 0.1, all of which are marked with gray circles. These outliers accounted for only 15.6% of the total data. The values in parentheses in Figure 6 represent the accuracy evaluation results after removing the gray-marked data, showing a significant improvement in accuracy (RMSE = 0.04, bias = 0.00). Generally, the MODIS time-share two-stage CI product shows high accuracy but has a slight tendency toward overestimation.  
Figure 7 shows the interannual variations in the time-share two-stage CIs and field-measured CIs at several sites. Across the four sites, the time-share two-stage CIs exhibited obvious CI\({}_{\text{LOS}}\) < CI\({}_{\text{LFS}}\) rules, further confirming that the CI can effectively capture the seasonal variation in vegetation. Of these, the SCBI site, classified as DBF, displayed the most pronounced difference between the CI\({}_{\text{LOS}}\) and CI\({}_{\text{LFS}}\), with the CI\({}_{\text{LOS}}\) consistently being smaller than the CI\({}_{\text{LFS}}\) throughout the 2001-2020 time series. The field-measured CIs are also closely aligned with the time-share two-stage CIs. Additionally, while there are some discrepancies between the field-measured CIs and the time-share two-stage CIs, these differences are mostly within one standard deviation, suggesting that the errors fall within an acceptable range. These errors may stem from the pooled field-measured CI data and uncertainties in the CI inversion process. Even though we selected field-measured CIs  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{3}{*}{**Year**} & \multirow{3}{*}{**Range**} & \multicolumn{4}{c}{**The First Vegetation Cycle**} & \multicolumn{4}{c}{**The Second Vegetation Cycle**} \\ \cline{3-10}  & & \multicolumn{2}{c}{**The First Algorithm**} & \multicolumn{2}{c}{**The Second Algorithm**} & \multicolumn{2}{c}{**The First Algorithm**} & \multicolumn{2}{c}{**The Second Algorithm**} \\ \cline{3-10}  & & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) < CI\({}_{\text{LIS}}\)**} & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) < CI\({}_{\text{LIS}}\)**} & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) > CI\({}_{\text{LIS}}\)**} & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) < CI\({}_{\text{LIS}}\)**} & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) < CI\({}_{\text{LIS}}\)**} & \multicolumn{2}{c}{**CI\({}_{\text{LOS}}\) > CI\({}_{\text{LIS}}\)**} \\ \hline \multirow{4}{*}{2008} & NH & 66.08\% & 33.92\% & 68.57\% & 77.43\% & 50.34\% & 49.66\% & 51.69\% & 48.31\% \\  & Trop & 65.37\% & 34.63\% & 66.73\% & 33.27\% & 58.31\% & 41.69\% & 59.49\% & 40.55\% \\  & SH & 73.76\% & 26.24\% & 74.15\% & 2 covering more than 3 months within the LOS or LFS, errors persist due to the large scale and the possibility that field-measured CIs may not be continuous data on a monthly scale.  
Figure 6: The accuracy evaluation results compared the time-share two-stage CIs with field-measured CIs, marking data overestimated or underestimated by more than 0.1 with gray dots (kinds of outliers). The values in parentheses represent the accuracy evaluation results after removing the gray-dotted data.  
Figure 7: Temporal variation in the time-share two-stage CIs at the (**a**) mixed forest, (**b**) woody savanna, (**c**) deciduous broadleaf forest, and (**d**) savanna field sites. Details of the field-measured CI data are shown in Appendix A. Red pentagons indicate the field-measured CI data. The black and blue dots indicate the CI\({}_{\text{LOS}}\) and CI\({}_{\text{LFS}}\), respectively.