## 3 Results and Discussion  
_Rainfall, Temperature and Radiation_  
The choice of the years 2009 and 2012 was based on previous analyses by [18], which identified these two years as having rainfall extremes. Specifically, 2009 exhibited a rainfall anomaly of approximately +400 mm while 2012 had an anomaly of approximately \(-400\) mm in the ESEC-Serido region. The selection of these years was primarily motivated by the influence of rainfall on energy and mass exchange (water vapor and CO\({}_{2}\)) in tropical regions, as demonstrated by studies conducted by [10; 20; 21]. Differences in rainfall amount and distribution were observed between the two study years (Figure 2). Annual rainfall in 2009 and 2012 were 1019.6 mm and 198.2 mm, respectively, while the mean annual climatological precipitation is 758 mm [32]. \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Parameters**} & \multicolumn{3}{c}{**Wet Season**} & **Dry Season** & \\ \cline{2-5}  & **Initial** & **CO\({}_{2}\) Flux Calibrated** & & \\ \hline Specific leaf area (sla) & 13.0 & 14.5 & 23.5 & [32; 43] \\ typical dimension of leaves (du) & 0.072 & 0.056 & 0.032 & [32; 44] \\ typical dimension of stems (ds) & 0.1 & 0.05 & 0.05 & [32; 44] \\ Leaf width (w) & 0.1 & 0.06 & 0.03 & [32; 44] \\ Stomatal conductance coefficient (m) & 10.0 & 8.0 & 4.0 & [17; 32; 43; 45] \\ Maximum capacity of the Rubisco enzyme (Vmax) & \(75\times 10^{-6}\) & \(90\times 10^{-6}\) & \(50\times 10^{-6}\) & [32; 43; 46] \\ Initial soil moisture fraction (\(\theta\)g/@d) & 0.36 & 0.225 & 0.105 & [32; 36; 47] \\ \hline \end{tabular}
\end{table} 
Table 1: Calibrated parameters: specific leaf area (sla, m\({}^{2}\) leaf kg\({}^{-1}\) C), typical dimension of leaves (du, m), typical dimension of stems (ds, m), leaf width (w, m), stomatal conductance coefficient (m, dimensionless), maximum capacity of the Rubisco enzyme (Vmax, \(\mu\)mol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-1}\)), and initial soil moisture fraction (\(\theta\)g/@d, dimensionless). \(\theta\)g is the mass-based soil water content expressed in gravimetric soil moisture content, \(\theta\)d is soil moisture content. Figure 2: Average monthly rainfall (mm) observed during the years 2009 and 2012 in Serido-RN. The months from February to May showed the highest volumes and a greater regularity in 2009 (857 mm--84% of total rainfall) and 2012 (98.60 mm--50% of total rainfall). In the dry season (from July to December), rainfall rarely occurs, with negligible values recorded in 2009 (102.20 mm--10% of total rainfall) and 2012 (2.20 mm--1% of total rainfall). Figure 3 illustrates the hourly cycle of global radiation (Rg) over the two years. It can be observed that Rg exhibited a similar behavior in both years. However, it is noteworthy that Rg was slightly higher in 2012 (490.20 Wm\({}^{-2}\)) compared to 2009 (466.50 Wm\({}^{-2}\)), which is likely associated with lower cloud cover in 2012. This is supported by the fact that rainfall in 2012 was substantially below both the climatological average and that of the year 2009 [18]. As expected, the air temperature in 2012 was also higher than in 2009 (Figure 4). The hourly cycle reveals that not only was the average temperature observed in 2012 higher than in 2009, but the minimum and maximum temperatures were also higher (23.6 \({}^{\circ}\)C and 35 \({}^{\circ}\)C, respectively) compared to 2009 (23.3 \({}^{\circ}\)C and 32 \({}^{\circ}\)C, respectively). This difference in air temperature is probably associated with the difference in rainfall between the two years. The daily cycle of meteorological variables is primarily influenced by Earth's rotation and, consequently, the daily cycle of solar radiation. However, the daily cycle of air temperature is also affected by longwave radiation, specifically ter  
Figure 4: Hourly cycle of mean air temperature (\({}^{\circ}\)C) observed during the years 2009 and 2012 in Seridó-RN. Figure 3: Annual mean hourly cycle of global solar radiation (Wm\({}^{-2}\)) observed during the years 2009 and 2012 in Seridó-RN. radiation.