Refractive index of aerosol particles over the Amazon tropical forest during LBA-EUSTACH 1999

Guyon, P, Boucher O, Graham B, Beck J, Mayol-Bracero OL, Roberts GC, Maenhaut W, Artaxo P, Andreae MO.  2003.  Refractive index of aerosol particles over the Amazon tropical forest during LBA-EUSTACH 1999. Journal of Aerosol Science. 34:883-907.

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absorption, aerosol, aerosol optical properties, biomass, brazil, burning, carbon, coefficient, in-situ, mineral, optical particle counter, optical-properties, particulate matter, scattering coefficient, size distribution, size distributions, smoke particles, transport


Optical properties of aerosol particles were characterized during two field campaigns at a remote rainforest site in Rond (o) over cap nia, Brazil, as part of the project European Studies on Trace Gases and Atmospheric Chemistry, a contribution to the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA-EUSTACH). The measurements included background (wet season), biomass burning (dry season), and transition period conditions. Optical measurements of light scattering and absorption were combined with data on number/size distributions in a new iterative method, which retrieves the effective imaginary refractive index of the particles at a wavelength of 545 nm. For ambient relative humidities lower than 80%, background aerosols exhibited an average refractive index of 1.42 - 0.006i. Biomass burning aerosols displayed a much larger imaginary part, with an average refractive index of 1.41 - 0.013i. Other climate-relevant parameters were estimated from Mie calculations. These include single-scattering albedos of 0.93 +/- 0.03 and 0.90 +/- 0.03 (at ambient humidity), asymmetry parameters of 0.63 +/- 0.02 and 0.70 +/- 0.03, and backscatter ratios of 0.12 +/- 0.01 and 0.08 +/- 0.01 for background and biomass burning aerosols, respectively. (C) 2003 Published by Elsevier Ltd.