Скачать или смотреть SoMAS / ITPA - Resolving the Local and Global Atmospheric Signatures of Amazon Deforestation

March 12 David Medvigy from the Department of Geosciences at Princeton University speaks to SoMAS on Wednesday, March 12, 2014.

Topic: "Resolving the Local and Global Atmospheric Signatures of Amazon Deforestation"

ABSTRACT: The Amazon River basin is the largest watershed in the world and plays an enormous role in local and global hydrological cycling. However, the Amazon rainforest has changed dramatically over the past few decades. Since the 1970s, about 20% of the Brazilian Amazon has been deforested. About 40% is expected to be deforested by 2050. Although numerical models have long predicted that the total deforestation of the Amazon would lead to basin-scale precipitation decreases and temperature increases, potential non-local effects of deforestation have been a matter of controversy. This talk will present some recent model simulations designed to highlight the impacts of Amazon deforestation on North American and South American climate. Our approach, which utilizes a variable resolution GCM, differs from previous studies that used uniform resolution GCMs or regional climate models. By using a variable resolution GCM, we are able to simulate regions of interest at high resolution, while simulating the rest of the world at a coarser, more computationally efficient resolution. Our analysis of North America focuses on the northwest United States. We find that 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 significant precipitation reductions for the coastal northwest United States and the Sierra Nevada during December-January-February. Meanwhile, in South America, we find that Amazon deforestation induces changes in the frequency and intensity of strong cold air incursions from the Pacific. Surprisingly, parts of southern South America that are far from the deforested area are significantly affected. Overall, our results highlight the need for adequate model resolution in modeling the impacts of Amazon deforestation and also suggest how Amazon deforestation might affect the climate of remote regions.