Abstract View
Humidity Dependent Absorption Enhancements for Brown Carbon Surrogates
KYLE GORKOWSKI, James D. Lee, Christian Carrico, Tyler Capek, Claudio Mazzoleni, Allison Aiken, Manvendra Dubey, Los Alamos National Lab
Abstract Number: 398
Working Group: Carbonaceous Aerosol
Abstract
Large uncertainties remain with aerosol optical properties and their relative humidity (RH) dependence that impact atmospheric radiative transfer significantly. These uncertainties are especially challenging for the humidity dependence of light absorption by brown carbon aerosols. To address these challenges, we report on laboratory optical measurements of surrogate brown carbon species as a function RH and a model framework to interpret them.
We used an RH-controlled single scattering albedometer to measure in-situ aerosol light extinction and scattering. This custom instrument was built utilizing a cavity-attenuated phase shift-single scattering albedo PM monitor (CAPS-PMSSA, Aerodyne, Inc.) at 450nm. We sampled three brown carbon surrogates (Sunset Yellow, Sodium Fluorescein, and Para Red); each was aerosolized and size selected, comprised of a single molecular species, and had a different hygroscopicity. For each species, we performed a combined optical and hygroscopic closure analysis. We compared the resulting hygroscopic responses to available thermodynamic models. The protocols established in this laboratory work will be applied during the 2021 DOE-ARM TRACER field campaign in Houston, Texas, to examine the effects of humidity on convectively processed absorbing aerosols.