Dependence of Aerosol Single Scattering Albedo on Biomass Combustion Efficiency: Laboratory and Field Studies
Abstract
Biomass burning (BB) is a major source of aerosols that are known to affect the radiative balance of the atmosphere. Quantitative and predictive understanding of the radiative effects of BB aerosols requires accurate knowledge of the input optical parameters in radiative transfer models, which are currently associated with large uncertainties. To address this problem, we study the optical properties of BB aerosols produced from controlled laboratory combustions and wildfires, with a focus on aerosol single scattering albedo (SSA), a critical parameter that determines the magnitude and sign of aerosols' climate forcing. SSA of BB aerosols produced from laboratory burning of 30 types of biomass with 99 individual burns and two wildfires have been measured and compared at multiple wavelengths. The laboratory measurements show that SSA spans from 0.2 to 1, with the variation depending strongly on combustion conditions and weakly on fuel types. Specifically, SSA decreases sharply with increasing combustion efficiency for the flaming phase aerosols due to the dynamic change of relative magnitude of black carbon and light absorbing organic components. In contrast, the smoldering phase emissions that are dominated by organics have relatively constant SSA values of approximately 0.95. Moreover, SSA shows considerable spectral variation between mid-visible and near-infrared wavelengths, with larger spectral dependence at higher combustion efficiency. Parameterization of SSA as a function of modified combustion efficiency is derived and shown to agree with field observations, making it possible for efficient evaluation of the climate impacts of BB aerosols using radiative-transfer modeling.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.A14A..02L
- Keywords:
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- 0305 ATMOSPHERIC COMPOSITION AND STRUCTURE Aerosols and particles;
- 0360 ATMOSPHERIC COMPOSITION AND STRUCTURE Radiation: transmission and scattering