Articles | Volume 16, issue 4
Atmos. Chem. Phys., 16, 2155–2174, 2016

Special issue: South AMerican Biomass Burning Analysis (SAMBBA)

Atmos. Chem. Phys., 16, 2155–2174, 2016

Research article 25 Feb 2016

Research article | 25 Feb 2016

On the vertical distribution of smoke in the Amazonian atmosphere during the dry season

Franco Marenco1, Ben Johnson2, Justin M. Langridge3, Jane Mulcahy4, Angela Benedetti5, Samuel Remy6, Luke Jones5, Kate Szpek3, Jim Haywood2,7, Karla Longo8, and Paulo Artaxo9 Franco Marenco et al.
  • 1Satellite Applications, Met Office, Exeter, UK
  • 2Earth System and Mitigation Science, Met Office Hadley Centre, Exeter, UK
  • 3Observational Based Research, Met Office, Exeter, UK
  • 4Earth System Core Development Group, Met Office Hadley Centre, Exeter, UK
  • 5European Centre for Medium-range Weather Forecasts, Reading, UK
  • 6Laboratoire de Météorologie Dynamique, UPMC/CNRS, Paris, France
  • 7College of Engineering, Maths and Physical Sciences, University of Exeter, Exeter, UK
  • 8Instituto Nacional de Pesquisas Espaciais, São José dos Campos, Brazil
  • 9Institute of Physics, University of São Paulo, São Paulo, Brazil

Abstract. Lidar observations of smoke aerosols have been analysed from six flights of the Facility for Airborne Atmospheric Measurements BAe-146 research aircraft over Brazil during the biomass burning season (September 2012). A large aerosol optical depth (AOD) was observed, typically ranging 0.4–0.9, along with a typical aerosol extinction coefficient of 100–400 Mm−1. The data highlight the persistent and widespread nature of the Amazonian haze, which had a consistent vertical structure, observed over a large distance ( ∼ 2200 km) during a period of 14 days. Aerosols were found near the surface; but the larger aerosol load was typically found in elevated layers that extended from 1–1.5 to 4–6 km. The measurements have been compared to model predictions with the Met Office Unified Model (MetUM) and the ECMWF-MACC model. The MetUM generally reproduced the vertical structure of the Amazonian haze observed with the lidar. The ECMWF-MACC model was also able to reproduce the general features of smoke plumes albeit with a small overestimation of the AOD. The models did not always capture localised features such as (i) smoke plumes originating from individual fires, and (ii) aerosols in the vicinity of clouds. In both these circumstances, peak extinction coefficients of the order of 1000–1500 Mm−1 and AODs as large as 1–1.8 were encountered, but these features were either underestimated or not captured in the model predictions. Smoke injection heights derived from the Global Fire Assimilation System (GFAS) for the region are compatible with the general height of the aerosol layers.

Short summary
A widespread and persistent smoke layer was observed in the Amazon region during the biomass burning season, spanning a distance of 2200 km and a period of 14 days. The larger smoke content was typically found in elevated layers, from 1–1.5 km to 4–6 km. Measurements have been compared to model predictions, and the latter were able to reproduce the general features of the smoke layer, but with some differences which are analysed and described in the paper.
Final-revised paper