Studying the impact of biomass burning aerosol radiative and climate effects on the Amazon rainforest productivity with an Earth system model

Author(s)

Malavelle, Florent F. ^[1] ; Haywood, Jim M. ^{[2, 1]} ; Mercado, Lina M. ^{[3, 4]} ; Folberth, Gerd A. ^[2] ; Bellouin, Nicolas ^[5] ; Sitch, Stephen ^[4] ; Artaxo, Paulo ^[6]

Affiliation

^[1] Univ Exeter, CEMPS, Exeter EX4 4QE, Devon - England

^[2] UK Met Off Hadley Ctr, Exeter EX1 3PB, Devon - England

^[3] Ctr Ecol & Hydrol, Wallingford OX10 8BB, Oxon - England

^[4] Univ Exeter, CLES, Exeter EX4 4RJ, Devon - England

^[5] Univ Reading, Dept Meteorol, Reading RG6 6BB, Berks - England

^[6] Univ Sao Paulo, Inst Phys, Dept Appl Phys, Sao Paulo - Brazil

• Document type: Journal article
• Source: Atmospheric Chemistry and Physics; v. 19, n. 2, p. 1301-1326, JAN 31 2019.
• Web of Science Citations: 2

Abstract

Diffuse light conditions can increase the efficiency of photosynthesis and carbon uptake by vegetation canopies. The diffuse fraction of photosynthetically active radiation (PAR) can be affected by either a change in the atmospheric aerosol burden and/or a change in cloudiness. During the dry season, a hotspot of biomass burning on the edges of the Amazon rainforest emits a complex mixture of aerosols and their precursors and climate-active trace gases (e.g. CO2, CH4, NOx). This creates potential for significant interactions between chemistry, aerosol, cloud, radiation and the biosphere across the Amazon region. The combined effects of biomass burning on the terrestrial carbon cycle for the present day are potentially large, yet poorly quantified. Here, we quantify such effects using the Met Office Hadley Centre Earth system model HadGEM2-ES, which provides a fully coupled framework with interactive aerosol, radiative transfer, dynamic vegetation, atmospheric chemistry and biogenic volatile organic compound emission components. Results show that for present day, defined as year 2000 climate, the overall net impact of biomass burning aerosols is to increase net primary productivity (NPP) by +80 to +105 TgC yr(-1), or 1.9% to 2.7 %, over the central Amazon Basin on annual mean. For the first time we show that this enhancement is the net result of multiple competing effects: an increase in diffuse light which stimulates photosynthetic activity in the shaded part of the canopy (+65 to +110 TgC yr(-1)), a reduction in the total amount of radiation (-52 to -105 TgC yr(-1)) which reduces photosynthesis and feedback from climate adjustments in response to the aerosol forcing which increases the efficiency of biochemical processes (+67 to +100 TgC yr(-1)). These results illustrate that despite a modest direct aerosol effect (the sum of the first two counteracting mechanisms), the overall net impact of biomass burning aerosols on vegetation is sizeable when indirect climate feedbacks are considered. We demonstrate that capturing the net impact of aerosols on vegetation should be assessed considering the system-wide behaviour. (AU)

• FAPESP's process: 13/05014-0 - GoAmazon: interactions of the urban plume of Manaus with biogenic forest emissions in Amazonia
• Grantee: Paulo Eduardo Artaxo Netto
• Support Opportunities: Research Program on Global Climate Change - Thematic Grants
• FAPESP's process: 12/14437-9 - Study of physico-chemical properties of biomass burning aerosols and the radiative forcing at the SAMBBA experiment - the South American Biomass Burning Analysis
• Grantee: Paulo Eduardo Artaxo Netto
• Support Opportunities: Research Program on Global Climate Change - Regular Grants