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Nature. 2016 Nov 17;539(7629):416-419. doi: 10.1038/nature19819. Epub 2016 Oct 24.

Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall.

Author information

1
Environmental and Climate Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
2
Department of Applied Environmental Science and Analytical Chemistry, Stockholm University, Stockholm 10691, Sweden.
3
University of São Paulo, São Paulo 05508-900, Brazil.
4
Biogeochemistry and Multiphase Chemistry Departments, Max Planck Institute for Chemistry, 55128 Mainz, Germany.
5
School of Atmospheric Sciences, Nanjing University, and Collaborative Innovation Center for Climate Change, Jiangsu Province, 210023, Nanjing, China.
6
Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
7
Department of Biogeochemical Systems, Max Planck Institute for Biogeochemistry, 07745 Jena, Germany.
8
Department of Physics, University of Helsinki, PO Box 64, FI-00014 Helsinki, Finland.
9
Amazonas State University, Amazonas 69050-020, Brazil.
10
Department of Chemistry, University of California, Irvine, California 92697, USA.
11
National Institute for Space Research, São José dos Campos, São Paulo 12227-010, Brazil.
12
Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093, USA.
13
School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.

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 atmosphere. 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 conditions, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear. 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.

PMID:
27776357
DOI:
10.1038/nature19819
[Indexed for MEDLINE]

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