Amazon boundary layer aerosol concentration sustained by vertical transport during rainfall
Rapid vertical transport of small aerosol particles from the free troposphere to the atmospheric boundary layer occurs during precipitation and maintains the population of aerosol particles over Amazonia. Aerosol particles over Amazonia The Amazon rainforest is one of the few continental regions whe...
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Published in | Nature (London) Vol. 539; no. 7629; pp. 416 - 419 |
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Main Authors | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
London
Nature Publishing Group UK
17.11.2016
Nature Publishing Group |
Subjects | |
Online Access | Get full text |
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Summary: | Rapid vertical transport of small aerosol particles from the free troposphere to the atmospheric boundary layer occurs during precipitation and maintains the population of aerosol particles over Amazonia.
Aerosol particles over Amazonia
The Amazon rainforest is one of the few continental regions where atmospheric aerosol processes 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 poorly understood. This paper reports rapid vertical transport of small aerosol particles 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 effect can help to maintain the population of aerosol particles in the pristine Amazon boundary layer, so may influence cloud properties and climate under natural conditions.
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
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. Most field studies of atmospheric aerosols over continents are influenced by atmospheric vapours of anthropogenic origin (for example, ref.
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) 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
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,
4
,
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, but the origin of small aerosol particles that grow into cloud condensation nuclei in the Amazon boundary layer remains unclear
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,
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,
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. 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. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 USDOE AC05-76RL01830 PNNL-SA-117828 |
ISSN: | 0028-0836 1476-4687 1476-4687 |
DOI: | 10.1038/nature19819 |