Following The Water that Evaporates from the Amazon Forest
Francina Dominguez1, Jorge Eiras-Barca1,2
1Department of Atmospheric Sciences, University of Illinois at Urbana-Champaign, IL.
2Environmental Physics Laboratory (EphysLab), Universidade de Vigo, Spain.
Precipitation recycling in the Amazon Forest has been the focus of research studies for more than four decades. It is now well established that a very large fraction of the precipitation within the Amazon originates from local evapotranspiration. However, only until recently have we been able to numerically “tag” Amazonian evapotranspiration at the high spatial and temporal scales necessary to better understand the variability of terrestrial moisture on the atmosphere and its interactions with the Andes Mountain Range. As deforestation continues to change the Amazon, it is critical to better understand the role of Amazonian evapotranspiration and how it might change as humans continue to modify land cover:
The Weather Research and Forecast (WRF) model, together with its Water Vapor Tracers (WVT) capability has been used to carry out two long-term 10-year (2004-2013) simulations of the South American continent with 20-km resolution. In the first simulation, we use satellite-derived land cover, while in the second simulation we use projected land use change for the year 2050 following a business as usual deforestation scenario. Throughout the simulations, the WVT tagged all evapotranspiration from the Amazon basin, providing the capacity to differentiate the ratio of local (Amazonian) water from total water. Thus, high-resolution recycling ratio average fields have been obtained for each season in the basin. The average recycling ratio for the Amazon is close to 30%, but substantial spatial variations highlight the importance of the Andes Mountain Range on the spatial distribution of water vapor of recycled origin. We find that deforestation dramatically influences all aspects of the Amazonian hydroclimate. Critically, total precipitation and precipitation of recycled origin decrease, during the wet season. Significant decrease in precipitation is particularly evident over the deforested regions. During the dry season, temperature shows the strongest signal, with higher temperatures over the deforested regions.