AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Long Term Measurements of Aerosol Optical Properties in Amazonian
PAULO ARTAXO, Luciana Rizzo, Erik Swietlicki, Andrea Arana, Elisa Sena, Glauber Cirino, Alfred Wiedensohler, Institute of Physics, University of Sao Paulo
Abstract Number: 579 Working Group: Remote and Regional Atmospheric Aerosols
Abstract Aerosol physical and chemical properties were measured in two sites in Amazonia since January 2008. The clean site is at Central Amazonia (Manaus) and is located in a pristine Amazonian forest site. A second sampling site is located in Porto Velho, Rondonia, an area strongly affected by biomass burning emissions. Long term measurements, from February 2008 are being carried out in these two sites, as part of the EUCAARI and AEROCLIMA projects.
In the pristine Amazonian atmosphere, aerosol scattering coefficients ranged between 1 and 200 Mm-1 at 450 nm, while absorption ranged between 1 and 20 Mm-1 at 637 nm. A strong seasonal behavior was observed, with greater aerosol loadings during the dry season (Jul-Nov) as compared to the wet season (Dec-Jun). During the wet season in Manaus, aerosol scattering (450 nm) and absorption (637 nm) coefficients averaged, respectively, 14 and 0.9 Mm-1. Angstrom exponents for scattering were lower during the wet season (1.6) in comparison to the dry season (1.9), which is consistent with the shift from biomass burning aerosols, predominant in the fine mode, to biogenic and dust aerosols, predominant in the coarse mode. Single scattering albedo, calculated at 637 nm, did not show a significant seasonal variation, averaging 0.86. In Porto Velho, even in the wet season it was possible to observe a strong impact from anthropogenic sources. AOT values at 550 nm above 3 are frequently observed in Porto Velho with AERONET sunphotometers. Black Carbon was measured at 20 ug/m3 in the dry season, showing strong aerosol absorption.
This work presents a general description of the aerosol optical properties in Amazonia, both during the Amazonian wet season, when the aerosol population is dominated by particles of biogenic origin, and during the dry season, when there is a strong influence of biomass burning emissions.