Articles | Volume 17, issue 23
Atmos. Chem. Phys., 17, 14785–14810, 2017

Special issue: Coupled chemistry–meteorology modelling: status and...

Atmos. Chem. Phys., 17, 14785–14810, 2017

Research article 12 Dec 2017

Research article | 12 Dec 2017

Modeling the radiative effects of biomass burning aerosols on carbon fluxes in the Amazon region

Demerval S. Moreira1,2, Karla M. Longo3,a, Saulo R. Freitas3,a, Marcia A. Yamasoe4, Lina M. Mercado5,6, Nilton E. Rosário7, Emauel Gloor8, Rosane S. M. Viana9, John B. Miller10, Luciana V. Gatti11,12, Kenia T. Wiedemann13, Lucas K. G. Domingues11,12, and Caio C. S. Correia11,12 Demerval S. Moreira et al.
  • 1Universidade Estadual Paulista (UNESP), Faculdade de Ciências, Bauru, SP, Brazil
  • 2Centro de Meteorologia de Bauru (IPMet), Bauru, SP, Brazil
  • 3Centro de Previsão de Tempo e Estudos Climáticos, Instituto Nacional de Pesquisas Espaciais (INPE), Cachoeira Paulista, SP, Brazil
  • 4Departamento de Ciências Atmosféricas do Institudo de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo (USP), São Paulo, SP, Brazil
  • 5Geography, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
  • 6Centre for Ecology and Hydrology (CEH), Wallingford, UK
  • 7Universidade Federal de São Paulo (UNIFESP), Campus Diadema, Diadema, SP, Brazil
  • 8School of Geography, University of Leeds, Woodhouse Lane, Leeds, UK
  • 9Departamento de Matemática, Universidade Federal de Viçosa (UFV), Viçosa, MG, Brazil
  • 10Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration (NOAA), Boulder, Colorado 80305, USA
  • 11Centro de Ciências do Sistema Terrestre, Instituto Nacional de Pesquisas Espaciais (INPE), São José dos Campos, SP, Brazil
  • 12Instituto de Pesquisas Energéticas e Nucleares (IPEN), Comissão Nacional de Energia Nuclear (CNEN), São Paulo, Brazil
  • 13Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA
  • anow at: Universities Space Research Association/Goddard Earth Sciences Technology and Research (USRA/GESTAR), Global Modeling and Assimilation Office, NASA Goddard Space Flight Center, Greenbelt, MD, USA

Abstract. Every year, a dense smoke haze covers a large portion of South America originating from fires in the Amazon Basin and central parts of Brazil during the dry biomass burning season between August and October. Over a large portion of South America, the average aerosol optical depth at 550 nm exceeds 1.0 during the fire season, while the background value during the rainy season is below 0.2. Biomass burning aerosol particles increase scattering and absorption of the incident solar radiation. The regional-scale aerosol layer reduces the amount of solar energy reaching the surface, cools the near-surface air, and increases the diffuse radiation fraction over a large disturbed area of the Amazon rainforest. These factors affect the energy and CO2 fluxes at the surface. In this work, we applied a fully integrated atmospheric model to assess the impact of biomass burning aerosols in CO2 fluxes in the Amazon region during 2010. We address the effects of the attenuation of global solar radiation and the enhancement of the diffuse solar radiation flux inside the vegetation canopy. Our results indicate that biomass burning aerosols led to increases of about 27 % in the gross primary productivity of Amazonia and 10 % in plant respiration as well as a decline in soil respiration of 3 %. Consequently, in our model Amazonia became a net carbon sink; net ecosystem exchange during September 2010 dropped from +101 to −104 TgC when the aerosol effects are considered, mainly due to the aerosol diffuse radiation effect. For the forest biome, our results point to a dominance of the diffuse radiation effect on CO2 fluxes, reaching a balance of 50–50 % between the diffuse and direct aerosol effects for high aerosol loads. For C3 grasses and savanna (cerrado), as expected, the contribution of the diffuse radiation effect is much lower, tending to zero with the increase in aerosol load. Taking all biomes together, our model shows the Amazon during the dry season, in the presence of high biomass burning aerosol loads, changing from being a source to being a sink of CO2 to the atmosphere.

Short summary
Fire in the Amazon forest produces a large amount of smoke that is released into the atmosphere and covers a large portion of South America for about 3 months each year. The smoke affects the energy and CO2 budgets. Using a numerical atmospheric model, we demonstrated that the smoke changes the forest from a source to a sink of CO2 to the atmosphere. The smoke ultimately acts to at least partially compensate for the forest carbon lost due to fire emissions.
Final-revised paper