ResumoO objetivo desse trabalho é avaliar a distribuição dos componentes do balanço de água e da reciclagem de precipitação na bacia amazônica, abordando os mecanismos físicos associados ao processo de reciclagem. De forma geral, a bacia amazônica se comporta como um sumidouro de umidade da atmosfera, recebendo vapor d'água tanto do transporte de origem oceânica quanto da evaportranspiração da floresta por meio do processo de reciclagem de precipitação. Em escala regional, a Amazônia representa uma importante fonte de umidade para outras regiões da América do Sul, contribuindo para o regime da precipitação em outras áreas do continente. Na média, a reciclagem de precipitação é da ordem de 20% na bacia amazônica, com valores variando entre 15% na porção norte e 40% na porção sul. Dessa forma, do total da precipitação na bacia, aproximadamente, 20% é decorrente do processo de evapotranspiração local; indicando que, a contribuição local para a precipitação total representa um percentual significativo no balanço de água regional e desempenha um importante papel no ciclo hidrológico amazônico. Entretanto, as variabilidades e mudanças no sistema climático devido tanto às variações naturais quanto antropogênicas (aumento na emissão de gases estufa e desflorestamento) podem afetar a reciclagem e o ciclo hdrológico regional. Palavras-chave: Amazônia, reciclagem de precipitação, transporte de umidade, interação biosfera-atmosfera, reanálises Era-Interim. Precipitation Recycling in the Amazon Basin: The Role of Moisture Transport and Surface Evapotranspiration AbstractThe objective of this study is to evaluate the distribution of water budget components and precipitation recycling in the Amazon basin addressing the physical mechanisms involved in the recycling process. In general, the Amazon basin acts as a sink for atmospheric moisture, receiving water vapor transported from the ocean and from precipitation recycled from evapotranspiration by the forest. At the regional scale, the Amazon basin is an important source of water vapor, contributing to precipitation in other remote locations of South America. Here we show, on average, 20% of precipitation in the Amazon basin is recycled, varying between 15% in the northern portion and 40% in the southern portion. Thus, approximately 20% of the total rainfall in the basin is derived from local evapotranspiration processes indicating that the local contribution to the total precipitation represents a significant contribution to the regional water budget and plays an important role in the Amazon hydrological cycle. However, the variability and changes in the climate system due to both natural and anthropogenic forcings (such as the increase in the concentration of greenhouse gases in the atmosphere and changes in land use and land cover -deforestation) can affect the precipitation recycling and regional hydrologic cycle.

The Brazilian Regional Atmospheric Modeling System (BRAMS) coupled with the dynamic vegetation scheme known as General Energy and Mass Transport Model (GEMTM) and land cover scenarios in the Amazon Basin and greenhouse gas concentration increase scenarios produced by Community Climate System Model of the National Center for Atmospheric Research are used to evaluate the impacts on the hydrological cycle of the Amazon Basin. The 2050 estimates of deforestation and the greenhouse gas concentration scenarios (A2) impact significantly the energy and moisture budgets. The dynamic structure of the atmosphere and consequently the moisture and mass convergence in the region are projected to be significantly different in 2050. The changes are more intense in the simulations with the combined effect of deforestation and greenhouse gas increase. In the deforestation scenario, a positive feedback is established in which changes in the regional circulation reduced the moisture convergence and precipitation in the region. In the increased greenhouse gas concentration scenario, with and without deforestation, a negative (positive) feedback is established in the rainy (dry) season in which the regional circulation changes (moisture convergence) are responsible for the reduction of precipitation. The results indicate that rapid destruction of the forest and the climate changes due to human activity can become irreversible, and that changes on hydrological cycle and perturbation in the complex relation between soil, plant and atmosphere can trigger significant changes in the ecosystems in the Amazon, once these systems do not present resilience or capacity to adapt to the magnitude of changes in the climate.Key words: Amazon basin, Deforestation, GHG Scenarios, IPCC-AR4, BRAMS. IMPACTOS NA COBERTURA VEGETAL E NAS MUDANÇAS DE CONCENTRAÇÃO DE GASES DE EFEITO ESTUFA (GEE) NO CICLO HIDROLÓGICO DA BACIA AMAZÔNICA: UM MODELO DE ESTUDO CLIMÁTICO REGIONAL RESUMO:O modelo regional BRAMS (Brazilian Regional Atmospheric Modeling System) acoplado ao esquema de vegetação dinâmica General Energy and Mass Transport Model (GEMTM) e cenários de usos da terra na Amazônia e de aumento na concentração dos gases do efeito estufa na atmosfera produzidos a partir das simulações climáticas do Modelo de Circulação Geral Community Climate System Model (CCSM3), do National Center for Atmospheric Research (NCAR), são utilizados para avaliar os impactos no ciclo hidrológico da _________________Revista Brasileira de Climatologia_________________ ISSN: 1980-055x (Impressa) 2237 Ano 10 -Vol. 15 -JUL/DEZ 2014 8 bacia amazônica. A projeção de desflorestamento para o ano de 2050 e cenário de emissão dos gases do efeito estufa (A2) afetam de forma significativa os balanços de energia e de água, a estrutura dinâmica da atmosfera e, consequentemente, a convergência de umidade e massa na bacia. As mudanças são mais intensas na simulação que existe o efeito combinando do desflorestamento e aumento dos gases do efeito estufa. No cenário de desflorestamento, o m...

The objective of this study is to evaluate the water budget components and to address the physical mechanisms involved in precipitation recycling in the Amazon basin using the European Centre reanalysis for Medium-Range Weather Forecasts – ECMWF for period 1980-2005. Precipitation recycling refers to the feedback mechanism between the Earth’s surface and the atmosphere wherein the amount of water that is evapotranspired from a given region of the surface returns to the same area in the form of precipitation. Here we show, on average, 20% of the total rainfall in the basin is derived from local evapotranspiration processes indicating that the local contribution to the total precipitation represents a significant contribution to the regional water budget and plays an important role in the Amazon water cycle. However, the changes in the climate system due to anthropogenic forcings such as the increase in the concentration of greenhouse gases in the atmosphere and changes in land use and land cover (i.e. deforestation) can affect the precipitation recycling. Although the results presented here have produced new knowledge about the interactions between surface processes and the hydrologic cycle, the effects of anthropogenic climate change on the precipitation recycling in the Amazon basin requires further investigation.