## 3 Results
### GPP Validation
#### 3.1.2 Seasonal GPP
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Site**} & \multirow{2}{*}{**Comparison**} & \multirow{2}{*}{**R\({}^{2}\)**} & \multicolumn{2}{c}{**Mean (SD)**} & \multicolumn{2}{c}{**Bias**} & \multirow{2}{*}{**RMSE (\%)**} & \multirow{2}{*}{**RE (\%)**} \\  & & & **(gC\(\cdot\) m\({}^{-2}\cdot\)8-day\({}^{-1}\))** & & & & \\ \hline \multirow{6}{*}{CB8} & Flux\_Tower vs. MOD\_NCEP & 0.76 ** & 29(30) vs. 24(25) & \(-5\) & 54 & 60 \\  & Flux\_Tower vs. MOD\_Tower & 0.83 ** & 29(30) vs. 16(19) & \(-13\) & 68 & 59 \\  & Flux\_Tower vs. NCEP\_GLASS & 0.84 ** & 29(30) vs. 28(30) & \(-1\) & 42 & 62 \\  & Flux\_Tower vs. Tower\_GLASS & 0.92 ** & 29(30) vs. 19(202) & \(-10\) & 50 & 58 \\ \hline \multirow{6}{*}{QYZ} & Flux\_Tower vs. MOD\_NCEP & 0.52 ** & 38(18) vs. 32(20) & \(-6\) & 41 & 34 \\  & Flux\_Tower vs. NOD\_Tower & 0.66 ** & 38(18) vs. 20(15) & \(-18\) & 55 & 54 \\  & Flux\_Tower vs. NCEP\_GLASS & 0.81 ** & 38(18) vs. 36(18) & \(-2\) & 22 & 18 \\  & Flux\_Tower vs. Tower\_GLASS & 0.87 ** & 38(18) vs. 28(15) & \(-16\) & 45 & 48 \\ \hline \multirow{6}{*}{DHS} & Flux\_Tower vs. MOD\_NCEP & 0.30 ** & 30(10) vs. 38(24) & 8 & 73 & 68 \\  & Flux\_Tower vs. MOD\_Tower & 0.42 ** & 30(10) vs. 27(19) & \(-3\) & 51 & 45 \\  & Flux\_Tower vs. NCEP\_GLASS & 0.55 ** & 30(10) vs. 55(15) & 25 & 90 & 95 \\  & Flux\_Tower vs. Tower\_GLASS & 0.75 ** & 30(10) vs. 36(17) & 6 & 39 & 27 \\ \hline \multirow{6}{*}{XSBN} & Flux\_Tower vs. MOD\_NCEP & - & 60(21) vs. 54(18) & \(-6\) & 49 & 41 \\  & Flux\_Tower vs. MOD\_Tower & - & 60(21) vs. 41(17) & \(-19\) & 55 & 38 \\  & Flux\_Tower vs. NCEP\_GLASS & 0.10 ** & 60(21) vs. 62(11) & 2 & 34 & 35 \\  & Flux\_Tower vs. Tower\_GLASS & 0.07 ** & 60(21) vs. 46(13) & \(-14\) & 43 & 31 \\ \hline \multirow{6}{*}{YC} & Flux\_Tower vs. MOD\_NCEP & 0.81 ** & 37(39) vs. 19(18) & \(-18\) & 80 & - \\  & Flux\_Tower vs. MOD\_Tower & 0.80 ** & 37(39) vs. 15(15) & \(-22\) & 93 & - \\  & Flux\_Tower vs. NCEP\_GLASS & 0.79 ** & 37(39) vs. 15(20) & \(-14\) & 72 & - \\  & Flux\_Tower vs. Tower\_GLASS & 0.77 ** & 37(39) vs. 21(19) & \(-16\) & 78 & - \\ \hline \multirow{6}{*}{HB} & Flux\_Tower vs. MOD\_NCEP & 0.95 ** & 12(16) vs. 12(17) & 0 & 31 & - \\  & Flux\_Tower vs. MOD\_Tower & 0.94 ** & 12(16) vs. 5(8) & \(-7\) & 92 & - \\  & Flux\_Tower vs. NCEP\_GLASS & 0.91 ** & 12(16) vs. 14(19) & 2 & 52 & - \\  & Flux\_Tower vs. Tower\_GLASS & 0.94 ** & 12(16) vs. 6(9) & \(-6\) & 84 & - \\ \hline \multirow{6}{*}{NMG} & Flux\_Tower vs. MOD\_NCEP & 0.73 ** & 59(9) vs. 8(10) & 3 & 124 & - \\  & Flux\_Tower vs. NMOD\_Tower & 0.75 ** & 5(9) vs. 7(9) & 2 & 106 & - \\ \cline{1-1}  & Flux\_Tower vs. NCEP\_GLASS & 0.65 ** & 5(9) vs. 6(8) & 1 & 112 & - \\ \cline{1-1}  & Flux\_Tower vs. Tower\_GLASS & 0.64 ** & 5(9) vs. 6(8) & 1 & 110 & - \\ \hline \multirow{6}{*}{DX} & Flux\_Tower vs. MOD\_NCEP & 0.89 ** & 4(6) vs. 24(4) & \(-2\) & 74 & - \\ \cline{1-1}  & Flux\_Tower vs. NOD\_Tower & 0.89 ** & 4(6) vs. 3(4) & \(0\) & 46 & - \\ \cline{1-1}  & Flux\_Tower vs. NCEP\_GLASS & 0.86 ** & 4(6) vs. 3(4) & \(-1\) & 65 & - \\ \cline{1-1}  & Flux\_Tower vs. Tower\_GLASS & 0.88 ** & 4(6) vs. 5(6) & 1 & 48 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of eight-day GPP derived from the tower estimates with those derived from the MODIS algorithms (MOD_NCEP GPP, MOD_Tower GPP, NCEP_GLASS GPP, and Tower_GLASS GPP) at eight sites. The full name for each site is listed in Table 1.  
underestimated by the MOD_NCEP GPP, MOD_Tower GPP and Tower_GLASS GPP algorithms (\(-143\) gC\(\cdot\) m\({}^{-2}\)\(\cdot\) 3-month\({}^{-1}\), \(-254\) gC\(\cdot\) m\({}^{-2}\)\(\cdot\) 3-month\({}^{-1}\) and \(-161\) gC\(\cdot\) m\({}^{-2}\)\(\cdot\) 3-month\({}^{-1}\), respectively) was that the measurements for CBS, QYZ, XSBN and YC were considerably underestimated (Figure 5a,b,d). * 3.