Preprints
https://doi.org/10.5194/acp-2022-530
https://doi.org/10.5194/acp-2022-530
08 Aug 2022
08 Aug 2022

Strong particle production and condensational growth in the upper troposphere sustained by biogenic VOCs from the canopy of the Amazon Basin

Yunfan Liu1, Hang Su2, Siwen Wang1, Chao Wei2, Wei Tao2, Mira L. Pöhlker2,6,7, Christopher Pöhlker2, Bruna A. Holanda2, Ovid O. Krüger2, Thorsten Hoffmann5, Manfred Wendisch7, Paulo Artaxo8, Ulrich Pöschl2, Meinrat O. Andreae3,4, and Yafang Cheng1 Yunfan Liu et al.
  • 1Minerva Research Group, Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 2Multiphase Chemistry Department, Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 3Max Planck Institute for Chemistry, 55128 Mainz, Germany
  • 4Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA
  • 5Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany
  • 6Experimental Aerosol and Cloud Microphysics Department, Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 7Faculty of Physics and Earth Sciences, Leipzig Institute for Meteorology, Leipzig University, Leipzig, Germany
  • 8Institute of Physics, University of São Paulo, São Paulo, Brazil

Abstract. Nucleation and condensation associated with biogenic volatile organic compounds (BVOCs) are important aerosol formation pathways, yet their contribution to the upper tropospheric aerosols remains inconclusive, hindering the understanding of aerosol climate effects. Here, we develop new schemes describing these organic aerosol formation processes in the WRF-Chem model and investigate their impact on the abundance of cloud condensation nuclei (CCN) in the upper troposphere (UT) over the Amazon Basin. We find that the new schemes significantly increase the simulated CCN number concentrations in the UT (e.g., up to ~400 cm-3 at 0.52 % supersaturation) and greatly improve the agreement with the aircraft observations. Organic condensation enhances the simulated CCN concentration by 90 % through promoting particle growth, while organic nucleation, by replenishing new particles, contributes an additional 14 %. Deep convection determines the rate of these organic aerosol formation processes in the UT through controlling the upward transport of biogenic precursors (i.e., BVOCs). This finding emphasizes the importance of the biosphere-atmosphere coupling in regulating upper tropospheric aerosol concentrations over the tropical forest and calls for attention to its potential role in anthropogenic climate change.

Journal article(s) based on this preprint

Yunfan Liu et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-530', Anonymous Referee #1, 23 Aug 2022
  • RC2: 'Comment on acp-2022-530', Eimear Dunne, 09 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision
AR by Lixia Liu on behalf of the Authors (12 Nov 2022)  Author's response    Author's tracked changes    Manuscript
ED: Referee Nomination & Report Request started (15 Nov 2022) by Martina Krämer
RR by Anonymous Referee #1 (15 Nov 2022)
RR by Eimear Dunne (22 Nov 2022)
ED: Publish as is (30 Nov 2022) by Martina Krämer
ED: Publish as is (30 Nov 2022) by James Allan(Executive Editor)

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-530', Anonymous Referee #1, 23 Aug 2022
  • RC2: 'Comment on acp-2022-530', Eimear Dunne, 09 Sep 2022

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision
AR by Lixia Liu on behalf of the Authors (12 Nov 2022)  Author's response    Author's tracked changes    Manuscript
ED: Referee Nomination & Report Request started (15 Nov 2022) by Martina Krämer
RR by Anonymous Referee #1 (15 Nov 2022)
RR by Eimear Dunne (22 Nov 2022)
ED: Publish as is (30 Nov 2022) by Martina Krämer
ED: Publish as is (30 Nov 2022) by James Allan(Executive Editor)

Journal article(s) based on this preprint

Yunfan Liu et al.

Yunfan Liu et al.

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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.

Executive editor
Traditionally, the interactions between aerosols, clouds, weather and climate has focused on sulphate aerosols. However, in the last 20 years it has become apparent that secondary organic aerosols are also highly abundant in the troposphere. These could represent a major coupling in the earth system between the biosphere and the atmosphere, and thus climate because forests are known to emit large quantities of biogenic VOCs that are known to produce secondary organic aerosols. However selectively studying their influence on the free troposphere is difficult as it requires in situ measurements aboard scientific aircraft. This study observes the role of biogenic secondary organic aerosols on the abundance of cloud condensation nuclei in the upper troposphere above the Amazon, and compares it with a state-of-the-art predictive model. This further supports the importance of these processes in earth system models and gives confidence that the current level of understanding will produce accurate predictions.
Short summary
The origins of the abundant cloud condensation nuclei (CCN) in the upper troposphere (UT) of the Amazon remain unclear. With model developments of new secondary organic aerosol schemes and constrained by observation, we show that the UT aerosol formation triggered by biogenic organics shapes the UT aerosols, and organic condensation is key for UT CCN production. This UT CCN-producing mechanism may prevail over broader vegetation canopies and deserves emphasis in aerosol-climate feedback.
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