## 3 Results
### Model Accuracy Comparison  
To examine the impact of spatial resolution of remote sensing pixels for EC footprints on modeling, we used our estimated parameters, optimized at 30 m and 500 m spatial resolution, respectively, pooled with corresponding Landsat-footprint-NDVI and MODIS-footprint-NDVI, to calculate GPP separately. The resulting GPP calculations were denoted GPPMC-30m and GPPMC-500m, respectively. The calculation of GPPMC-30m and GPPMC-500m used the same meteorological data (temperature, VPD, air atmospheric pressure, and CO\({}_{2}\) concentration) as driving data for fair comparison; the difference between GPPMC-30m and GPPMC-500m lay in the optimized parameters, Landsat-footprint-NDVI, and MODIS-footprint-NDVI. We compared the accuracies of GPPMC-30m and GPPMC-500m at 16 days and calculated the R\({}^{2}\) and RMSE for each of 78 sites. On average, GPPMC-30m and GPPMC-500m explained 75% and 70% of the variance in site-based GPP across all 78 sites, respectively, indicating that the Landsat-footprint NDVI resulted in better GPP simulation performance than the MODIS-footprint NDVI (Figure 5). Compared with GPPMC-500m, GPPMC-30m exhibited higher R\({}^{2}\) values and lower RMSE values at most sites, particularly at the DE-Kli (R\({}^{2}\) = 0.88, RMSE = 3.21 g C/m\({}^{2}\)/16 day), US-Ne2 (R\({}^{2}\) = 0.82, RMSE = 2.65 g C/m\({}^{2}\)/16 day), and US-Ne3 (R\({}^{2}\) = 0.87, RMSE = 2.30 g C/m\({}^{2}\)/16 day) cropland sites, at the US-Myb (R\({}^{2}\) = 0.73, RMSE = 2.62 g C/m\({}^{2}\)/16 day) and US-Tw1 (R\({}^{2}\) = 0.86, RMSE = 1.70 g C/m\({}^{2}\)/16 day) wetland sites, and at the AU-Cpr (R\({}^{2}\) = 0.92, RMSE = 0.74 g C/m\({}^{2}\)/16 day) and SN-Dhr ( R\({}^{2}\) = 0.83, RMSE = 1.62 g C/m\({}^{2}\)/16 day) savanna sites. Among the ten vegetation types, GPPMC-30m explained significantly higher variance in tower GPP for C3, C4, WET, SAV, SHR, and EBF ecosystems than GPPMC-500m, but with slightly higher variance in DBF, ENF, MF, and GRA \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Vegetation**} & \multirow{2}{*}{**Site**} & \multicolumn{3}{c}{**30 m Spatial Resolution**} & \multicolumn{3}{c}{**500 m Spatial Resolution**} \\ \cline{3-8}  & & \(\varepsilon_{\text{max}}\) & \(\theta\) & VPD0 & \(\varepsilon_{\text{max}}\) & \(\theta\) & VPD0 \\
**Type** & & **Number** & **(g C/MJ)** & **(ppm)** & **(k Pa)** & **(g C/MJ)** & **(ppm)** & **(k Pa)** \\ \hline EBF & 3 & 3.67 \(\pm\) 0.59 & 24.25 \(\pm\) 7.72 & 0.33 \(\pm\) 0.09 & 3.65 \(\pm\) 0.59 & 25.27 \(\pm\) 7.81 & 0.35 \(\pm\) 0.09 \\ DBF & 12 & 2.97 \(\pm\) 0.21 & 51.90 \(\pm\) 6.72 & 1.59 \(\pm\) 0.09 & 3.04 \(\pm\) 0.23 & 51.05 \(\pm\) 7.21 & 1.58 \(\pm\) 0.09 \\ ENF & 21 & 2.97 \(\pm\) 0.18 & 35.97 \(\pm\) 3.26 & 1.08 \(\pm\) 0.15 & 2.90 \(\pm\) 0.19 & 31.93 \(\pm\) 5.23 & 1.30 \(\pm\) 0.17 \\ MF & 5 & 2.79 \(\pm\) 0.21 & 43.31 \(\pm\) 6.07 & 1.34 \(\pm\) 0.12 & 2.83 \(\pm\) 0.19 & 43.65 \(\pm\) 5.45 & 1.34 \(\pm\) 0.13 \\ GRA & 14 & 4.59 \(\pm\) 0.06 & 64.72 \(\pm\) 0.63 & 1.09 \(\pm\) 0.01 & 4.44 \(\pm\) 0.08 & 64.72 \(\pm\) 0.75 & 1.09 \(\pm\) 0.01 \\ SAV & 3 & 3.19 \(\pm\) 0.30 & 25.39 \(\pm\) 5.25 & 1.55 \(\pm\) 0.15 & 2.60 \(\pm\) 0.24 & 25.35 \(\pm\) 5.29 & 1.56 \(\pm\) 0.14 \\ SHR & 4 & 2.16 \(\pm\) 0.33 & 57.59 \(\pm\) 14.18 & 1.26 \(\pm\) 0.23 & 2.02 \(\pm\) 0.32 & 58.01 \(\pm\) 14.23 & 1.24 \(\pm\) 0.23 \\ WET & 9 & 3.10 \(\pm\) 0.19 & 59.66 \(\pm\) 5.15 & 1.40 \(\pm\) 0.08 & 2.96 \(\pm\) 0.18 & 59.71 \(\pm\) 5.17 & 1.41 \(\pm\) 0.07 \\ C3 Crop & 3 & 3.57 \(\pm\) 0.29 & 60.55 \(\pm\) 5.18 & 1.34 \(\pm\) 0.18 & 3.27 \(\pm\) 0.19 & 62.63 \(\pm\) 4.75 & 1.37 \(\pm\) 0.18 \\ C4 Crop & 4 & 4.81 \(\pm\) 0.35 & 50.28 \(\pm\) 5.74 & 1.52 \(\pm\) 0.14 & 4.47 \(\pm\) 0.30 & 51.12 \(\pm\) 5.70 & 1.54 \(\pm\) 0.15 \\ \hline \end{tabular}
\end{table} 
Table 1: The mean value and standard deviations of estimated parameters for revised EC-LUE model at 30 m spatial resolution (Landsat) and 500 m spatial resolution (MODIS).