Análise do controle ambiental nas trocas de energia, vapor d’água e CO2 em área de caatinga.

Abstract

The analyses made in this study were aimed at quantifying aspects of the dynamics of the water, energy and carbonic gas (CO2) in the caatinga bioma. The factorial analysis by principal components was chosen as the fundamental tool in the characterization of the dependence between the atmospheric conditions and the hydric availability, and the detection of patterns related to sources and sinks of CO2. Three physical factors dominated the processes of mass (CO2 and water vapour) and energy exchange between the caatinga and the atmosphere during daytime. The aggregate variables that emerged in the first factor have association with turbulent transports within the convective boundary layer generated mainly by the thermal effect, convective cells and water vapour concentration in the atmosphere. The variables with higher factor loadings in the second factor are indicative of the evapotranspiration processes and are highly influenced by the seasonal cycle since the water transfer to the atmosphere is controlled by the vegetation stomata or by the energy availability, depending on the period. The aggregate variables of the third factor indicate that the energy transfer to the atmosphere as sensible heat is modulated by the longwave radiation. The results obtained in the analysis of the evolution of the CO2 flux allowed the conclusion that, although with minima rates, the bioma acts as a source of CO2 during the dry period. Substantially higher values (negative) observed during the rainy period indicate an opposite behaviour in which the bioma acts as a sink of atmospheric CO2 (CO2 sequestration). This result reflects the importance of the caatinga conservation for global warming control.