## 3 Results
### Evaluation of DIMONA PB Model Performance  
The statistics of linear regressions of simulated on observed ecosystem GPP, as well as RMSE and Willmott's d values, are summarized for the 2000-2004 period and for each individual year for VBSall_WT (Table 3), VBSall_NS (Table 4), and the other runs listed in Table 2 (Table 5). For the entire 2000-2004 period, slopes varying between 1.01 and 1.02 for _DIMONA_ hourly WT-driven model runs (Tables 3 and 5) and between 0.94 and 0.97 for hourly near-surface \(\theta\)-driven model runs (Tables 4 and 5) are comparable to previous modelling studies with _ecosys_[10]. However, the corresponding intercepts in this study are larger by \(\sim\)1 umol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-1}\). Respectively, R\({}^{2}\) varying between 0.67 and 0.69 and Willmott's d varying between 0.86 and 0.88 for _DIMONA_ hourly WT-driven and near-surface \(\theta\)-driven model runs are only slightly lower than those for _ecosys_[10], where the RMSE for modelled GPP was not reported. The values of R\({}^{2}\) and Willmott's d improved for both VBall_WT and VBall_NS when individual years were analyzed, reaching 0.72 and 0.92, respectively (Tables 3 and 4). A slight decrease in intercepts was accompanied by a slight increase in slopes. However, the overestimation of simulated GPP was less than that reported for other models, varying between 20% and 61% [50], or even greater overestimations with satellite-derived GPP [51; 52]. The slopes for the daily linear regressions with VBall_WT and VBall_NS were even larger (Tables 3 and 4), and artifacts of daily aggregations from hourly EC-derived GPP possibly played some role. Daily R\({}^{2}\) and Willmott's d values for VBall_WT and VBall_NS varied between 0.82 and 0.84 and between 0.87 and 0.91, respectively, for 2000-2004, with maximum values of 0.91 and 0.95, respectively, for individual years (Tables 3 and 4). These results suggest reasonable model performance at a daily time scale and no significant hourly autocorrelation. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Model Run Name** & **Period** & **Time Step** & **a** & **b** & **R\({}^{2}\)** & **RMSE** & **d** \\ \hline VBall\_NS & 2000–2004 & hourly & 0.94 & 1.39 & 0.69 & 1.70 & 0.88 \\ \hline VBall\_NS & 2000 & hourly & 0.98 & 1.77 & 0.64 & 2.30 & 0.83 \\ \hline VBall\_NS & 2001 & hourly & 1.02 & 1.19 & 0.71 & 2.10 & 0.88 \\ \hline VBall\_NS & 2002 & hourly & 1.11 & 1.27 & 0.66 & 2.67 & 0.83 \\ \hline VBall\_NS & 2003 & hourly & 1.07 & 1.31 & 0.72 & 2.07 & 0.86 \\ \hline VBall\_NS & 2004 & hourly & 0.87 & 1.24 & 0.72 & 2.24 & 0.92 \\ \hline VBall\_NS & 2000–2004 & daily & 1.17 & 0.27 & 0.84 & 0.84 & 0.91 \\ \hline VBall\_NS & 2000 & daily & 1.25 & 0.36 & 0.82 & 0.89 & 0.87 \\ \hline VBall\_NS & 2001 & daily & 1.28 & 0.22 & 0.84 & 0.84 & 0.87 \\ \hline VBall\_NS & 2002 & daily & 1.16 & 0.12 & 0.85 & 0.72 & 0.93 \\ \hline VBall\_NS & 2003 & daily & 1.28 & 0.23 & 0.89 & 0.71 & 0.90 \\ \hline VBall\_NS & 2004 & daily & 1.03 & 0.24 & 0.87 & 0.83 & 0.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistics for estimating the performance of the representative model run driven by the near-surface soil water content (\(\theta\)) as a hydrological driver, including slope a (unitless), intercept b (umol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-1}\) for hourly time step, g C m\({}^{-2}\) d\({}^{-1}\) for daily time step), and coefficient of determination, R\({}^{2}\) (unitless), of the linear regressions of simulated on eddy covariance (EC)-derived ecosystem GPP, root mean square error, RMSE (umol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-1}\) for hourly time step, g C m\({}^{-2}\) d\({}^{-1}\) for daily time step), and [PERSON]’s index of agreement d (unitless).