Chemical and optical aging of forest fire plumes
Abstract
During recent aircraft-based projects, we have penetrated fresh fire plumes, followed them for tens of kilometers, and sampled them thousands of kms from their sources. Chemical analysis with an Aerosol Mass Spectrometer (AMS) for non-refractory composition and a Single Particle Soot Photometer (SP2) alongside nephelometers and a Particle Soot Absorption Spectrometer (PSAP) for optical properties of the aerosol show consistent changes in particle properties as they age. We use BC to normalize for dilution and scavenging, as it is unlikely to be created outside of the fire. Chemical changes are rapid within the first 50 minutes as the organic matter becomes more oxygenated. Single Scatter Albedo rises concurrently which reflects increasing non-absorbing aerosol mass. Somewhat unexpectedly, the absorption Ăngstrom exponent (between 470 and 660 nm) also rises, indicating that the complex aromatic organic material, sometimes referred to as Brown Carbon, either takes some time to condense or has its absorption amplified as other material condenses upon it. At long range from the source, biomass burning plumes can be significant sources of CCN to remote areas even when diluted and scavenged to such an extent that direct optical effects are inconsequential.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.A23C..06H
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE / Aerosols and particles;
- 0322 ATMOSPHERIC COMPOSITION AND STRUCTURE / Constituent sources and sinks;
- 0368 ATMOSPHERIC COMPOSITION AND STRUCTURE / Troposphere: constituent transport and chemistry;
- 0478 BIOGEOSCIENCES / Pollution: urban;
- regional and global