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The image with orbital track date of 02/11/1994 shown the lowest value of H (69.7 W m-2) for bare soil (Figure 5b). This low value may have been occurred due to an above average annual precipitation in the region in addition to a cumulative precipitation of 17.83 mm occurred in the previous 20 days (Table 1). Values of H were below 300 W m-2 in most images. It was observed that H averages for bare soil areas were higher than those of the irrigated areas. According to Arraes (2010), such a fact is explained by the absence of vegetal cover in this area, with almost all available energy being used for air and soil heating.

Figure 5 The image with orbital track date of 02/11/1994 shown the lowest value of H (69.7 W m-2) for bare soil (Figure 5b). This low value may have been occurred due to an above average annual precipitation in the region in addition to a cumulative precipitation of 17.83 mm occurred in the previous 20 days (Table 1). Values of H were below 300 W m-2 in most images. It was observed that H averages for bare soil areas were higher than those of the irrigated areas. According to Arraes (2010), such a fact is explained by the absence of vegetal cover in this area, with almost all available energy being used for air and soil heating.

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The EB components were obtained using the SEBAL algorithm and a Fortran 90 language program was developed to retrieve data of the study area. The climate of the region is of AW type, rainy tropical, with maximum and = minimum average temperatures of 34 °C and 18 °C, and maximum and minimum average relative humidity of 80% and 49% respectively (RAMOS; SANTOS, 1993). According to Mont'Alverne (1996), the rainy season is comprised between January and May and the dry season between September and November, with an average annual rainfall of 1,033 mm.
The EB components were obtained using the SEBAL algorithm and a Fortran 90 language program was developed to retrieve data of the study area. The climate of the region is of AW type, rainy tropical, with maximum and = minimum average temperatures of 34 °C and 18 °C, and maximum and minimum average relative humidity of 80% and 49% respectively (RAMOS; SANTOS, 1993). According to Mont'Alverne (1996), the rainy season is comprised between January and May and the dry season between September and November, with an average annual rainfall of 1,033 mm.
Figure 2. Annual precipitation values obtained at FUNCEME at the Barbalha-CE station
Figure 2. Annual precipitation values obtained at FUNCEME at the Barbalha-CE station
Figure 3 (b) shows that Rn average values for bare soil areas fluctuates between 538.7 and 638.2 W m-2. The reduced vegetal cover provides a lower capacity to reduce surface temperature and directly affects the surface net radiation.
Figure 3 (b) shows that Rn average values for bare soil areas fluctuates between 538.7 and 638.2 W m-2. The reduced vegetal cover provides a lower capacity to reduce surface temperature and directly affects the surface net radiation.
Figure 4 - Time distribution of heat flux in the soil between 1993 and 2014 for irrigated area (a) and exposed soil (b). The G estimations in the bare soil areas ranged from 52.9 to 94.9 W m-2 (figure 4b). Silva and Bezerra (2006), studying energy balance components in semi-arid regions, obtained averaged values
Figure 4 - Time distribution of heat flux in the soil between 1993 and 2014 for irrigated area (a) and exposed soil (b). The G estimations in the bare soil areas ranged from 52.9 to 94.9 W m-2 (figure 4b). Silva and Bezerra (2006), studying energy balance components in semi-arid regions, obtained averaged values
Figura 6 - Distribvicdo temporal do fluxo calor latente no periodo entre 1993 a 2014 para drea irrigada (a) e solo exposto (b). The averages of latent heat flux component (LE) for bare soil are shown in Figure 6b. A decrease in the average values of LE was observed during the period and it may be related to deforestation processes and_ intensification of agricultural exploitation that the plateau has been suffering over the years. The highest LE average was 479.3 W m-2 at 02/11/1994. Such value can be justified by the occurrence of a cumulative precipitation of 17.3mm.
Figura 6 - Distribvicdo temporal do fluxo calor latente no periodo entre 1993 a 2014 para drea irrigada (a) e solo exposto (b). The averages of latent heat flux component (LE) for bare soil are shown in Figure 6b. A decrease in the average values of LE was observed during the period and it may be related to deforestation processes and_ intensification of agricultural exploitation that the plateau has been suffering over the years. The highest LE average was 479.3 W m-2 at 02/11/1994. Such value can be justified by the occurrence of a cumulative precipitation of 17.3mm.
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