10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
UV-Vis-IR Spectral Complex Refractive Indices and Optical Properties of Brown Carbon Aerosol from Biomass Burning
YULI W. HEINSON, Benjamin Sumlin, Nishit Shetty, Apoorva Pandey, Brent Williams, Rajan K. Chakrabarty, Washington University in Saint Louis
Abstract Number: 984 Working Group: Carbonaceous Aerosol
Abstract BrC aerosols have a significant uncertainty on radiative forcing and climate models. Constraining the complex refractive indices, optical properties and size of brown carbon (BrC) aerosols is a vital endeavor for improving climate models and satellite retrieval algorithms. Smoldering peatlands have been identified as a major emission source of these aerosol. The fuel parameters such as moisture content, source depth, geographic origin, and fuel packing density of the wildland fuels could influence the properties of emitted aerosol. We measured in situ spectral (375-1047 nm) optical properties of BrC aerosols emitted from smoldering combustion of Boreal and Indonesian peatlands across a range of the fuel parameters. Inverse Lorenz-Mie algorithms used these optical measurements along with simultaneously measured particle size distributions to retrieve the aerosol complex refractive indices (m=n+iκ). Our results show that the real part n is constrained between 1.5 and 1.7 with no obvious functionality in wavelength (λ), moisture content, source depth, or fuel packing density (FPD). With increasing λ from 375 to 532 nm, κ decreased from 0.014 to 0.003 following the Kramers-Kronig dispersion relation for the damped simple harmonic oscillator, with a corresponding increase in single scattering albedo (SSA) from 0.93 to 0.99. For λ ≥ 532 nm, both κ and SSA show no spectral dependency.