Laboratory and Ambient Comparison of Hygroscopicity and Optical Properties of Aerosols

We report humidified optical measurements taken in Houston during DOE ARM's TRACER-CAT campaign in July 2022. An increase in aerosol scattering and extinction and single scatter albedo with humidity are quantified and related to their composition. Changes in absorption with humidity are more complex and depend on the composition of the mixed aerosols. Humidity effects that rely on aerosol size, composition, hygroscopicity, and refractive index are computed in models by assuming a mixing state (e. g. external, internal or core-shell) of and the component properties. We compare the humidified optical properties with the collocated HT-DMA and CCNc measurements to understand the water's impact on the physicochemical properties.