Evaluation of Arctic Aerosol Mass Scattering Efficiency using Airborne Observations

LUKE ZIEMBA, Matthew Brown, Josh DiGangi, Glenn Diskin, Eva-Lou Edwards, Francesca Gallo, Susan Mathai, Richard Moore, Amin Nehrir, Michael Shook, Armin Sorooshian, Jian Wang, Edward Winstead, NASA

     Abstract Number: 480
     Working Group: Remote and Regional Atmospheric Aerosol

Abstract
The climate impact of ambient aerosols depends on the composition, size, and vertical distribution of the particles in the atmosphere. To compute radiative effects, global climate models often need to translate between particle mass concentrations and optical properties using empirically- or theoretically-derived mass scattering (and absorption) efficiencies. But, inherent in this process are assumptions regarding the material properties of the aerosol mixture, the particle size distribution, and the vertical profile of aerosols in the atmosphere. Assessing the mass scattering efficiency is especially challenging in the Arctic, where mass concentrations are low and remote sensing validation is difficult. Here, we use airborne observations made from the NASA P3 aircraft during the ARCSIX (Arctic Radiation Cloud aerosol Surface Interaction Experiment) campaign in 2024 based at Pituffik Space Base in northwest Greenland. Speciated aerosol mass concentration and size distribution measurements, combined with measurements of scattering coefficient, are used to assess assumed mass scattering efficiencies. Measurements of particle refractive index are used to corroborate Mie Theory calculations. Seasonal differences (i.e., between spring and summer) and the vertical profile are discussed. Finally, sub-saturated hygroscopicity measurements are used to extrapolate dry measurements to ambient RH, and in-situ extinction profiles are compared to coincident lidar observations.