Abstract:
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.

Author Keywords:
aerosol optical properties, scattering coefficient, absorption coefficient, size distribution, optical particle counter, biomass burning

KeyWords Plus:
SIZE DISTRIBUTIONS, OPTICAL-PROPERTIES, PARTICULATE MATTER, MINERAL AEROSOL, SMOKE PARTICLES, IN-SITU, TRANSPORT, BRAZIL, CARBON, ABSORPTION

Addresses:
Guyon P, Max Planck Inst Chem, Dept Biogeochem, POB 3060 Biogeochem, D-55020 Mainz, Germany
Max Planck Inst Chem, Dept Biogeochem, D-55020 Mainz, Germany
Max Planck Inst Chem, Dept Atmospher Chem, Mainz, Germany
USTL, CNRS, Opt Atmospher Lab, Villeneuve Dascq, France
State Univ Ghent, Inst Nucl Sci, Ghent, Belgium
Univ Sao Paulo, Inst Phys, Sao Paulo, Brazil

Publisher:
PERGAMON-ELSEVIER SCIENCE LTD, THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND

IDS Number:
703VK

ISSN:
0021-8502