Abstract View
Ground-based in Situ Hyperspectral Optical Measurements of Smoke Aerosols during FIREX-AQ, Relating Spectral Characteristics to Aerosol Composition, Fuels, and Fire State
CAROLYN JORDAN, Bruce Anderson, John Barrick, Kathleen Brunke, Jiajue Chai, Gao Chen, Ewan Crosbie, Jack Dibb, Ann Dillner, Emily Gargulinski, Jackson Kaspari, Robert Martin, Richard Moore, Rachel O'Brien, Claire Robinson, Gregory Schuster, Taylor Shingler, Michael Shook, Amber Soja, Kenneth Thornhill, Andrew Weakley, Elizabeth Wiggins, Edward Winstead, Luke Ziemba, et al., NASA
Abstract Number: 378
Working Group: Wildfire Aerosols
Abstract
A recent study from the Korea – United States Ocean Color (KORUS-OC) field campaign explored using two-dimensional mapping of in situ aerosol hyperspectral (300-700 nm) characteristics to provide additional discrimination between differing ambient aerosol populations than can be provided by the use of Ångström exponents alone. Here, we apply that methodology to smoke aerosol samples collected from the NASA Langley Research Center’s (LaRC) Mobile Aerosol Characterization (MACH-2) laboratory during the western portion of the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign in July and August of 2019. MACH-2 traveled over 7000 miles sampling 8 fires in 6 states. Here, we report hyperspectral absorption coefficients measured in a liquid waveguide capillary cell from deionized water and methanol extracts of aerosols collected on Teflon filters from 5 of those fires: Williams Flats in Washington state, Nethker in Idaho, Little Bear in Utah, Castle in Arizona, and 204 Cow in Oregon. We also report commensurate mean in situ hyperspectral extinction coefficients for those filter samples obtained from our custom spectral extinction instrument (SpEx). Second order polynomials were used to fit each of the logarithmically transformed spectra, along with the traditional linear fits known as Ångström exponents. Samples from each fire mapped into distinct regions in the two-parameter (a1,a2) fit space of the second order polynomial fit coefficients. Variations in aerosol composition deriving from differing biomass fuels, fire state, and atmospheric processing are explored to interpret the separation found in (a1,a2) space. In addition, residuals (the difference between the fit and measured spectrum) from the second order polynomials more clearly reveal individual spectral features than are evident from residuals from the linear fits. These features provide specific wavelength targets for further exploration of relationships to physicochemical aerosol properties.