Aerosol characteristics and particle production in the upper troposphere over the Amazon Basin

Autor(en)

Meinrat O. Andreae, Armin Afchine, Rachel Albrecht, Bruna Amorim Holanda, Paulo Artaxo, Henrique M. J. Barbosa, Stephan Bormann, Micael Amore Cecchini, Anja Costa, Maximilian Dollner, Daniel Fütterer, Emma Järvinen, Tina Jurkat, Thomas Klimach, Tobias Konemann, Christoph Knote, Martina Krämer, Trismono Krisna, Luiz A. T. Machado, Stephan Mertes, Andreas Minikin, Christopher Pöhlker, Mira L. Pöhlker, Ulrich Pöschl, Daniel Rosenfeld, Daniel Sauer, Hans Schlager, Martin Schnaiter, Johannes Schneider, Christiane Schulz, Antonio Spanu, Vinicius B. Sperling, Christiane Voigt, Adrian Walser, Jian Wang, Bernadett Weinzierl, Manfred Wendisch, Helmut Ziereis

Abstrakt

Airborne observations over the Amazon Basin showed high aerosol particle concentrations in the upper troposphere (UT) between 8 and 15 km altitude, with number densities (normalized to standard temperature and pressure) often exceeding those in the planetary boundary layer (PBL) by one or two orders of magnitude. The measurements were made during the German-Brazilian cooperative aircraft campaign ACRIDICON-CHUVA on the German High Altitude and Long Range Research Aircraft (HALO). The campaign took place in September/October 2014, with the objective of studying tropical deep convective clouds over the Amazon rainforest and their interactions with atmospheric trace gases, aerosol particles, and atmospheric radiation.

 

Aerosol enhancements were observed consistently on all flights during which the UT was probed, using several aerosol metrics, including condensation nuclei (CN) and cloud condensation nuclei (CCN) number concentrations and chemical species mass concentrations. The UT particles differed in their chemical composition and size distribution from those in the PBL, ruling out convective transport of combustion-derived particles from the BL as a source. The air in the immediate outflow of deep convective clouds was depleted in aerosol particles, whereas strongly enhanced number concentrations of small particles (< 90 nm diameter) were found in UT regions that had experienced outflow from deep convection in the preceding 5–72 hours. We also found elevated concentrations of larger (> 90 nm) particles in the UT, which consisted mostly of organic matter and nitrate and were very effective CCN.

 

Our findings suggest a conceptual model, where production of new aerosol particles takes place in the UT from volatile material brought up by deep convection, which is converted to condensable species in the UT. Subsequently, downward mixing and transport of upper tropospheric aerosol can be a source of particles to the PBL, where they increase in size by the condensation of biogenic volatile organic carbon (BVOC) oxidation products. This may be an important source of aerosol particles in the Amazonian PBL, where aerosol nucleation and new particle formation has not been observed. We propose that this may have been the dominant process supplying secondary aerosol particles in the pristine atmosphere, making clouds the dominant control of both removal and production of atmospheric particles.

Organisation(en)

Aerosolphysik und Umweltphysik

Externe Organisation(en)

Forschungszentrum Jülich, Universidade Federal de São Paulo, Max-Planck-Institut für Chemie (Otto-Hahn-Institut), University of California, San Diego, Instituto Nacional de Pesquisas Espaciais (INPE), Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Ludwig-Maximilians-Universität München, Universität Leipzig, Leibniz-Institut für Troposphärenforschung, Brookhaven National Laboratory, Karlsruher Institut für Technologie, Hebrew University Jerusalem, Johannes Gutenberg-Universität Mainz

Journal

Atmospheric Chemistry and Physics

Band

18

Seiten

921-961

Anzahl der Seiten

41

ISSN

1680-7316

DOI

https://doi.org/10.5194/acp-18-921-2018

Publikationsdatum

2017

Peer-reviewed

Ja

ÖFOS 2012

103037 Umweltphysik, 103039 Aerosolphysik, 105206 Meteorologie

Schlagwörter

ASJC Scopus Sachgebiete

Atmospheric Science

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/2358dc5f-abb4-41ba-a8c8-d2ca3f1cf0e2