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Instituto Nacional de Pesquisas Espaciais (INPE) 2013

Avaliação dos impactos das mudanças dos usos e cobertura da terra no clima da região semiárida do Brasil

Amaral Cunha Ana Paula Martins do

Titre : Avaliação dos impactos das mudanças dos usos e cobertura da terra no clima da região semiárida do Brasil

Auteur : Amaral Cunha Ana Paula Martins do

Institution de soutenance : Instituto Nacional de Pesquisas Espaciais (INPE)

Grade : Tesis de doctorado 2013

Résumé
The continental surface vegetal cover has been considerably changed by human activities, mainly through natural vegetation conversion in grasslands and farming areas. Such changes in surface cover may impact the regional and global climates, through of the changes in biophysical processes and CO2 exchanges between vegetation and atmosphere. Based on that, the main objective of this work was to investigate the impacts of such land cover and land use changes (LCLUC) on surface processes and on the climate of Brazil´s semiarid region. As the first step, the IBIS calibration for the semiarid natural caatinga was performed, by the use of a multi-objective calibration algorithm, named OPTIS. The new set of calibrated parameters was applied in the second step´s simulation of this work. In this second step, three experiments were performed using offline IBIS, considering the conversion from caatinga (natural vegetation) to agroecosystem and to degraded caatinga. The experiments results show that the observed changes, mainly concerning the surface albedo (increasing), have modified the components of energy balance. Besides that, the changes in roughness length and in vegetation stomatic properties strengthen the changes observed in turbulent and CO2 exchange between surface and atmosphere. In the third and last part of this work, with the objective of evaluating the LCLUC responses on surface processes, considering the atmospheric feedbacks, two experiments of vegetal cover conversion were performed, using the AGCM/CPTEC/IBIS. The first one, named “CURRENT” was performed to evaluate the impacts on farming activities spreading in semiarid. The second one, named “ FUTURE” had the objective of studying the impacts of a degraded caatinga associated with a farming spreading scenario. In general, the simulation results showed that the LCLUC, due to the changes in relevant surface variables, has caused alterations in local and neighborhood regions climate. The natural vegetation conversion (forests and caatinga) to agroecosystem leads to increase in the annual mean of rainfall in the rainy season and to a decrease in the dry season. In degraded caatinga conversion, it was observed a rainfall decreasing in annual mean as in seasonal means. The most distinct impacts from LCLUC on temperature near to surface has occurred on the conversion from the forest to the agroecosystem, where the temperature has decreased 1.2ºC, in annual mean. From natural caatinga to agroecosystem conversion, the temperature near to surface has decreased 0.2ºC. In the degraded caatinga scenario, this temperature has increased 0.2ºC. The simulation results also pointed that the forests to agroecosystem conversion as well as the degraded caatinga strengthens the decreasing of raw primary productivity and, as consequence, the decreasing of net primary productivity. The opposite was observed in the natural caatinga to degraded caatinga conversion. Finally, this current study has opened a path to the better understanding of biophysical processes changes and CO2 changes due to ther surface cover modification, which may cause large scale alterations in energy balance, water and carbon in NEB region.

Mots clés : mudanças dos usos da terra modelos Climáticos nordeste do Brasil semiárido land use change climate models Brazil northeast semi-arid Meteorologia

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Page publiée le 26 janvier 2015, mise à jour le 4 juillet 2017