AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Aerosol Optical Properties of Biomass Smoke from Southwestern U.S. Fuels
JARED LAM, Christian Carrico, Samantha Bixler, Dian Romonosky, Allison Aiken, Thom Rahn, Manvendra Dubey, New Mexico Institute of Mining and Technology
Abstract Number: 761 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract Biomass burning aerosol emissions are a critical driver of the climate system and have atmospheric effects on visibility and human health. Here we investigated physical and optical properties of smoke from flaming and smoldering combustion from both native and invasive plant species. A 3-wavelength total-backscatter nephelometer (TSI Model 3563) measured total and backscatter coefficients at wavelengths of 450nm, 550nm, and 750nm. Integrating parallel measurements from light absorption and extinction techniques, the extinction budget was dominated by light scattering by particles (smoldering cases) and had a larger light absorption by particles (flaming cases). Intensive aerosol optical properties measured here include the Ångström exponent (Å) and backscatter fraction (b) which parameterize aerosol effects on climate. Replicate experiments (n=10) showed considerable variation in the magnitudes of extensive optical properties such as light extinction coefficient, though nearly identical temporal profiles when normalized to the peak. In testing repeatability, intensive parameters including Å and b were much more tightly constrained with coefficient of variance values around 0.02. The wavelength dependence of optical properties was very steep due to the size distributions of emissions, with mean diameters from approximately 25 to 150nm and driven by combustion phase. Across all burns, flaming fuels typically generate Å ~ 2.4-2.5 while smoldering fuels generate Å greater than 3. Typical backscatter fractions were 0.16-0.19 and 0.20-0.24 respectively. Filter samples of sub-micrometer smoke composition and fuel species influence are under investigation. The measurements provide key aerosol parameters and enhance our understanding of biomass burning aerosols in our atmosphere and their climate significance.