Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall
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Date
2016-10-24
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Citation of Original Publication
Wang, Jian, Radovan Krejci, Scott Giangrande, Chongai Kuang, Henrique M. J. Barbosa, Joel Brito, Samara Carbone, et al. “Amazon Boundary Layer Aerosol Concentration Sustained by Vertical Transport during Rainfall.” Nature 539, no. 7629 (October 24, 2016): 416–19. https://doi.org/10.1038/nature19819.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
The nucleation of atmospheric vapours is an important source of new aerosol particles that can subsequently grow to form cloud condensation nuclei in the atmosphere1. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref. 2) and, in consequence, aerosol processes in pristine, terrestrial environments remain poorly understood. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions3,4,5, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear6,7,8. Here we present aircraft- and ground-based measurements under clean conditions during the wet season in the central Amazon basin. We find that high concentrations of small aerosol particles (with diameters of less than 50 nanometres) in the lower free troposphere are transported from the free troposphere into the boundary layer during precipitation events by strong convective downdrafts and weaker downward motions in the trailing stratiform region. This rapid vertical transport can help to maintain the population of particles in the pristine Amazon boundary layer, and may therefore influence cloud properties and climate under natural conditions.