Potential precipitation reductions in the northwest U.S. in response to the large-scale deforestation of the Amazon

Wednesday, 16 December 2015: 15:10
2008 (Moscone West)
David Medvigy1, Robert L Walko2, Roni Avissar2 and Martin J Otte3, (1)Princeton University, Geosciences, Princeton, NJ, United States, (2)University of Miami, Miami, FL, United States, (3)Environmental Protection Agency Research Triangle Park, Research Triangle Park, NC, United States
Numerical models have long predicted that the deforestation of the Amazon would lead to large regional changes in precipitation and temperature, but the extratropical effects of deforestation have been a matter of controversy. Here, we use a numerical model to simulate the potential effects of deforestation on the northwest United States December–February climate. Integrations are carried out using the Ocean–Land Atmosphere Model (OLAM), run as a variable-resolution atmospheric GCM. When the Amazon is simulated at < 50 km resolution, deforestation causes a redistribution of precipitation within the Amazon, accompanied by vorticity and thermal anomalies. These anomalies set up Rossby waves that propagate into the extratropics and impact western North America. Ultimately, Amazon deforestation results in 10%–20% precipitation reductions for the coastal northwest United States and the Sierra Nevada. However, when the Amazon is simulated at coarse resolution, this mechanism is not resolved and precipitation is not reduced in the northwest United States. These results highlight the need for adequate model resolution in modeling the impacts of Amazon deforestation. It is concluded that the deforestation of the Amazon may act as a driver of regional climate change in the extratropics, including areas of the western United States that are agriculturally important. Such ecoclimate teleconnections warrant further investigation.