Changes in South American Hydroclimate under Projected Amazonian Deforestation

Continued deforestation in the Amazon forest impacts the subsurface/surface and atmospheric branches of the hydrologic cycle. In the coupled land-atmosphere system, the sign and magnitude of the changes depends on the complex interactions between the water/energy and momentum budgets. To understand these changes, a set of two Weather Research and Forecast Water Vapor Tracers tool (WRF-VT) eulerian simulations have been run covering the South American continent throughout the period 2004-2013 with a spatial resolution of ~ 20 km. The water vapor tracers allow us to isolate the changes in atmospheric moisture. Simulation number 1 is a control simulation with the current temporally-varying MODIS-based conditions of land use for the Amazon basin. In simulation number 2, a modification of the MODIS land use has been carried out to simulate a deforestation scenario projected by the LC-14 "business-as-usual" by 2050.

Results project important changes in evapotranspiration, particularly in March, April and May for precipitation and June, July and August for evaporation. In the simulations, some deforested areas experience changes of -25% in total amount of both precipitation and evapotranspiration. By contrast, other regions will undergo the opposite change, and will see equivalent but positive anomalies in both variables when compared to current conditions. Changes in both evapotranspiration and precipitation are not limited to deforested grid points or surrounding areas. Alterations in land use result in alteration of the thermodynamic conditions of the entire continent, which translate, for example, into the enhancement of precipitation in the La Plata river basin.

Generally speaking, the northern and southern regions of the Amazon basin show a different response to deforestation. This differences can be mostly explained by the unequal behavior of the seasonal cycles of precipitation and evapotranspiration between both sectors.