## 4 Results
### Attribution of Detected High XCO\({}_{2}\) Units by Surface Extremes  
We attribute extreme high XCO\({}_{2}\) units to local reduced carbon uptake and/or increased carbon release, within at least a portion of the region identified. Some potential local drivers, including temperature, drought index, BA and GPP, are used to discuss the possible local extreme climate over detected extreme XCO\({}_{2}\) units. Monthly mean values of parameters and its normal value (calculated with all data in a given month during the study period) over the detected extreme high XCO\({}_{2}\) units from 2009 to 2016 are shown in Figures 4 and 5. The statistics of the driver anomalies during detected extreme periods and its comparison to the overall fluctuation is shown in Table 2.  
Figure 3: Temporal change of spatial mean dXCO\({}_{2}\) (red line) and XCO\({}_{2}\) (black line) over the covered area, with influenced time more than 15 days, for the ten largest events from June 2009 to May 2016. Extreme high XCO\({}_{2}\) is characterized with dXCO\({}_{2}\). The duration of the extreme events are highlighted with dashed vertical lines. (**a**) Ex-1: Forest and Cropland; (**b**) Ex-2: Sparse Shrub-land; (**c**) Ex-3: Savanna and Shrub-land; (**d**) Ex-4: Savanna; (**e**) Ex-5: Bare land; (**f**) Ex-6: Grassland and Shrub-land; (**g**) Ex-7: Forest; (**h**) Ex-8: Shrub-land and Savanna; (**i**) Ex-9: Forest and Shrub-land; (**j**) Ex-10: Forest and cropland. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & **Period** & **Grids NUM (Location)** & **dXCO\({}_{2}\) (ppm)** & **Z Score** & **\(\Delta\)Temp (IO)** & **\(\kappa\)PDSI** & **\(\Delta\)RA (Z/grid)** & **\(\Delta\)GFP (G/cm\({}^{3}\))** \\ \hline E-k: Forest and Ceopland & 10 July-10 October & 11361 & \(1.7\pm 0.39\) & \(2.4\pm 0.39\) & \(1.22\pm 1.60\) & \(-1.11\pm 0.18\) & \(8.77\pm 7.82\) & \(-5.85\pm 4.94\) \\  & & 21-34\% & & & & & & \\ \hline Ex-2: Sparse Strunk-lund & 16 January–16 April & 11-35\% & \(1.28\pm 0.21\) & \(2.31\pm 0.30\) & \(1.88\pm 0.70\) & \(-1.68\pm 0.14\) & \(-1.21\pm 20.39\) & \(-5.99\pm 3.32\) \\  & & & & & & & & \\ \hline Ex-3: Savanna and Strunk-lund & 1 February–16 May & \((5\)-35\% & \(1.37\pm 0.27\) & \(2.38\pm 0.36\) & \(1.93\pm 0.96\) & \(-2.10\pm 0.02\) & \(1.63\pm 2.43\) & \(-19.15\pm 13.64\) \\  & & & & & & & & \\ \hline Ex-k: Savanna & 15 November–16 May & \((5\)-25\% & \(1.40\pm 0.23\) & \(2.32\pm 0.33\) & \(1.56\pm 1.84\) & \(-1.31\pm 0.46\) & \(1.64\pm 2.82\) & \(-26.66\pm 18.97\) \\  & & & & & & & & \\ \hline Ex-k: Rare land & 16 March-16 May & \((26\)-47\% N & \(1.49\pm 0.30\) & \(2.37\pm 0.34\) & \(0.56\pm 0.86\) & \(0.63\pm 0.13\) & \(7.32\pm 19.17\) & \(-0.37\pm 0.72\) \\  & & & & & & & & \\ \hline Ex-6: Grassland and Strunk-lund & 16 February–16 May & \((17\)-35\% & \(1.30\pm 0.27\) & \(2.48\pm 0.42\) & \(0.54\pm 1.84\) & \(1.53\pm 0.19\) & \(-0.71\pm 0.58\) & \(-16.02\pm 6.15\) \\  & & & & & & & & \\ \hline Ex-7: Forest & 10 August–10 October & \((11\)-5\% & \(1.68\pm 0.34\) & \(2.32\pm 0.27\) & \(1.13\pm 1.11\) & \(-0.71\pm 0.21\) & \(-0.01\pm 0.03\) & \(-4.99\pm 9.74\) \\  & & & & & & & & \\ \hline Ex-8: Strunk-lund and Swanna & 9 September–9 December & \((21\)-35\% & \(1.39\pm 0.25\) & \(2.36\pm 0.34\) & \(1.78\pm 0.80\) & \(-1.96\pm 0.44\) & \(57.47\pm 106.69\) & \(-11.50\pm 5.31\) \\  & & & & & & & & \\ \hline Ex-9: Forest and Strunk-lund & 13 April–13 July & \((29\)-40\% N & \(1.40\pm 0.25\) & \(2.31\pm 0.31\) & \(-0.39\pm 0.85\) & \(-0.65\pm 0.28\) & \(15.35\pm 21.58\) & \(-2.87\pm 2.15\) \\  & & & & & & & & \\ \hline Ex-10: Forest and copeland & 16 March-16 May & \((6\)-28\% N & \(1.61\pm 0.29\) & \(2.31\pm 0.29\) & \(2.55\pm 1.07\) & \(-0.94\pm 0.10\) & \(-3.62\pm 25.08\) & \(-26.91\pm 20.88\) \\  & & & & & & & & \\ \hline \end{tabular}
\end{table} 
Table 2: Time and space features of detected extreme units (Ex) 1 through 10.