Preprints
https://doi.org/10.5194/acp-2021-138
https://doi.org/10.5194/acp-2021-138

  24 Mar 2021

24 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

The Response of the Amazon Ecosystem to the Photosynthetically Active Radiation Fields: Integrating Impacts of Biomass Burning Aerosol and Clouds in the NASA GEOS ESM 

Huisheng Bian1,2, Eunjee Lee3,4, Randal D. Koster4, Donifan Barahona4, Mian Chin2, Peter R. Colarco2, Anton Darmenov2, Sarith Mahanama5,4, Michael Manyin5,4, Peter Norris3,4, John Shilling6, Hongbin Yu2, and Fanwei Zeng5,4 Huisheng Bian et al.
  • 1Joint Center for Environmental Technology UMBC, Baltimore, MD, 21250, USA
  • 2Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA
  • 3Goddard Earth Sciences Technology and Research, Universities Space Research Association, Columbia, MD 21046, USA
  • 4Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
  • 5Science Systems and Applications, Inc., Lanham, MD 20706, USA
  • 6Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA

Abstract. The Amazon experiences fires every year, and the resulting biomass burning aerosols, together with cloud particles, influence the penetration of sunlight through the atmosphere, increasing the ratio of diffuse to direct photosynthetically active radiation (PAR) reaching the vegetation canopy and thereby potentially increasing ecosystem productivity. In this study, we use the NASA Goddard Earth Observing System (GEOS) model running with coupled aerosol, cloud, radiation, and ecosystem modules to investigate the impact of Amazon biomass burning aerosols on ecosystem productivity, as well as the role of the Amazon’s clouds in tempering the impact. The study focuses on a seven-year period (2010–2016) during which the Amazon experienced a variety of dynamic environments (e.g., La Niña, normal years, and El Niño). The radiative impacts of biomass burning aerosols on ecosystem productivity – call here the aerosol light fertilizer effect – are found to increase Amazonian Gross Primary Production (GPP) by 2.6 % via a 3.8 % increase in diffuse PAR (DFPAR) despite a 5.4 % decrease in direct PAR (DRPAR) on multiyear average. On a monthly basis, this increase in GPP can be as large as 9.9 % (occurring in August 2010). Consequently, the net primary production (NPP) in the Amazon is increased by 1.5 %, or ~92 TgCyr−1– equivalent to ~37 % of the carbon lost due to Amazon fires over the seven years considered. Clouds, however, strongly regulate the effectiveness of the aerosol light fertilizer effect. The efficiency of the fertilizer effect is highest for cloud-free conditions and linearly decreases with increasing cloud amount until the cloud fraction reaches ~0.8, at which point the aerosol-influenced light changes from being a stimulator to an inhibitor of plant growth. Nevertheless, interannual changes in the overall strength of the aerosol light fertilizer effect are primarily controlled by the large interannual changes in biomass burning aerosols rather than by changes in cloudiness during the studied period.

Huisheng Bian et al.

Status: open (until 26 Jun 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-138', Anonymous Referee #1, 27 Apr 2021 reply
  • RC2: 'Comment on acp-2021-138', Anonymous Referee #2, 12 Jun 2021 reply

Huisheng Bian et al.

Huisheng Bian et al.

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Short summary
The study using the NASA Earth System Model shows ~2.6 % increase of burning season gross
primary production and ~1.5 % increase of annual net primary production across the Amazon
Basin during 2010–2016 due to the change of surface downward direct and diffuse
photosynthetically active radiation by biomass burning aerosols. Such aerosol effect is strongly
dependent on the presence of clouds. The cloud fraction at which aerosols switch from
stimulating to inhibiting plant growth occurs at ~0.8. 
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