## 3 Results and Discussion
### Daily Variations and Seasonal Dynamics of Simulated Energy Fluxes
These discrepancies in the non-calibrated model happened mainly because under conditions of low water availability a higher portion of the net solar radiation is converted to H. Our results were consistent with observational analysis in a tropical semi-deciduous forest in the southern Amazon Basin performed according to the literature ([PERSON] et al., 2017). These authors reported that LE was overestimated by 40% and H was underestimated by 66%. The discrepancy between observed and simulated H and LE values was observed in other studies using the SITE model in the Amazon rainforest ([PERSON] et al., 2017) and also using other models in other ecosystems, such as temperate grasslands ([PERSON] et al., 2017). Figure 6: Simulations with calibration (solid red lines) for the wet season (simulation V) and dry season (simulation U) and eddy covariance observations (solid black lines) of monthly mean values of energy fluxes of 2015. Net radiation (Rn; (**A**)), sensible heat flux (H; (**B**)), latent heat flux (LE; (**C**)) and soil heat flux (G; (**D**)). For details on the calibrated parameters of simulations V and. As discussed in the literature [70], throughout the annual cycle, LE behaves as a function of annual mean rainfall due to water limitations observed in tropical savanna ecosystems during the dry season. In addition, the energy flux partition is directly associated to vegetation characteristics and land use changes [16; 33]. The occurrence of higher H values in arid and semiarid regions is a consequence of the reduction in water availability caused by low rainfall in these regions. Some studies show that in the Caatinga most of the available energy is converted into sensible heat flux in the dry season [33; 34]. A similar trend of decreasing LE during the dry season was reported in the literature [34], which studied energy balance components in a preserved Caatinga region. These mechanisms of LE variability were satisfactorily simulated in the present study. During the months with low water availability, the non-calibrated model greatly underestimates H. The default input parameters probably lead to the simulation of an ecosystem facing a higher water stress in relation to the Caatinga observational data. Thus, the use of specific parameters (e.g., reduced initial fraction of soil moisture--g/@d) during the calibration of the model was necessary to improve its performance in simulating LE. The same issue when adjusting variations in H and LE values during the dry season was reported for simulations of energy fluxes using the SITE model in a semi-deciduous tropical forest in the Amazon [53]. The seasonality of rainfall and light greatly affect leaf morphology and physiology in the Caatinga species. During the dry season, the Caatinga vegetation, which consists primarily of deciduous and semi-deciduous species, reaches its minimum level of physiological activity, which in turn is barely sufficient for the maintenance of leaves. Indeed, leaves become shorter, narrower and smaller, leading to a significant decrease in the specific leaf area [61; 63]. Under these conditions, transpiration rates in the Caatinga are very close zero [62; 71]. The direct effect of these characteristics is the reduction of LE, with Rn being mostly converted into H.