## 3 Results and Discussion
### Daily Variations and Seasonal Dynamics of Simulated Energy Fluxes
For details on the calibrated parameters of simulation U, see Table 2.  
Figure 3: Simulations without calibration (dashed blue lines), simulations with calibration (dashed red lines, simulation V) and eddy covariance observations (solid black lines) of mean daily cycle of energy fluxes during the wet season of 2014. Net radiation (Rn; (**A**)), sensible heat flux (H; (**B**)), latent heat flux (LE; (**C**)) and soil heat flux (G, (**D**)). Vertical bars indicate the standard deviation of fluxes. For details on the calibrated parameters of simulation V, see Table 2.  
The differences found between observed and simulated LE and H values during the day may be due to the fact that the model does not consider the daily variations of some parameters inherent to the ecosystem, such as the fraction of soil moisture. In the Caatinga biome, soil moisture decreases during the day, as reported by others [39; 65; 66]. This may explain the slight overestimation of LE after 12h00 in the wet season (Figure 3C). Similar difficulties when adjusting the hourly data variability was reported in flux simulations using the SITE model in a tropical semi-deciduous forest in the southern Amazon Basin [53] and also using other models, such as the Noah-MP, over a forest site in the Amazon [67] and integrated biosphere simulator (IBIS) for a Brazilian semiarid region [68]. The mean monthly values of the energy fluxes are presented in Figures 5 and 6. Table 4 shows the mean seasonal values of observed (and simulated) for the years 2014 and 2015 of the components of the energy balance. Mean seasonal Rn values ranged from 164.6 W m\({}^{-2}\) (172.5 W m\({}^{-2}\)) and 162.6 W m\({}^{-2}\) (173.5 W m\({}^{-2}\)) in the wet season of 2014 and 2015 to 168.7 W m\({}^{-2}\) (167.4 W m\({}^  
The mean simulated H fluxes in the wet season (58.8 W m\({}^{-2}\) in 2014 and 67.8 W m\({}^{-2}\) in 2015) were similar to observed values (59.7 W m\({}^{-2}\) in 2014 and 64.6 W m\({}^{-2}\) in 2015) (Table 4). There was a statistically significant difference between the means of H fluxes during the dry period, in which the simulated mean value was 91.9 W m\({}^{-2}\) in 2014 and 94.4 W m\({}^{-2}\) in 2015 while the observed value was 113.7 W m\({}^{-2}\) and 120.0 W m\({}^{-2}\), respectively for 2014 and 2015 (Table 4). Minimum (maximum) H (LE) values occurred during the wet season, while maximum (minimum) values occurred in the dry season. This reduction in LE and increased in H during the dry period is attributed to lower water availability in the soil due to the absence of rainfall over the Caatinga biome. In addition, we verified a statistically significant difference between simulated and observed LE mean values in the dry period (Table 4). Table 3 shows that the error statistics of H and LE between eddy covariance observations and simulations with the parameters set after calibration for the years 2014 and 2015 (values in parenthesis) presented a MAE value of 50.52(46.94), RMSE 68.83(71.97), \(r\) 0.85(0.91) and \(d\) 0.89(0.89) for H, and MAE value of 29.97(24.25), RMSE 65.99(53.48), \(r\) 0.69(0.74) and \(d\) 0.72(0.74) for LE. In general, mean seasonal G values were low, less than 10.0 W m\({}^{-2}\) and with a monthly variability similar to that featured by H. The highest G values occurred during the dry season, period in which leaf senescence occurs in the Caatinga and the soil is more exposed to radiation. The analysis of G fluxes simulated by the model showed no statistically significant difference between simulated and observed values (Table 4). Both the underestimation and overestimation of H and LE retrieved using the non-calibrated model (dashed blue lines, Figure 5) were greatly reduced with the adjustment of the SITE model according to specific wet season and dry season parameters (Figures 5 and 6). The model was run twice, and the specific forecasts of each season were merged.