The Future of the Amazon Basin Hydroclimatology

State-of-the art socio-economic scenarios of land-cover change in the Amazon Basin for the years 2030 and 2050 are used together with the Regional Atmospheric Modeling System (RAMS) to anticipate the hydrometeorological changes caused by deforestation expansion in that region assuming a four-year sequence (1997-2000) of meteorological conditions that include both El Niño and La Niña events. The basin-average rainfall decreases progressively with the increase of deforestation from the current state to 2030, 2050 and on to total deforestation. However, the spatial distribution of rainfall is significantly affected by the land-cover type, topography, and the predominant climate regime. While the massively deforested region experiences an important decrease of precipitation, the areas at the edge of that region and at elevated regions receive more rainfall. Propagating squall-lines over the massively deforested region dissipate before reaching the western part of the basin, causing a significant decrease of rainfall in that region. During El Niño events, the basin suffers a stronger decrease in rainfall as deforestation increases. The horizontal gradient of surface heat fluxes created by the deforestation pattern generates important circulations that are not resolved by global climate models (GCMs). An analysis of convergence and net energy shows that GCMs are more sensitive to deforestation than RAMS, mostly because of this lack of feedback.