Black Carbon Aerosols Properties for Remote Sensing and Radiative Forcing Applications
HANS MOOSMÜLLER, Greg Schuster, Eduard Chemyakin, Snorre Stamnes, Jacek Chowdhary,
Desert Research Institute Abstract Number: 516
Working Group: Aerosols, Clouds and Climate
AbstractMaterial and morphological properties of light absorbing particles in the atmosphere determine their single scattering albedo, asymmetry parameter, and direct radiative forcing, thereby affecting climate change predictions and mitigation. A quantitative understanding of aerosol optical properties is also needed for their global quantification through satellite and ground-based remote sensing. The dominant light absorbing aerosol is black carbon (BC) that has non-spherical, fractal-like shapes that complicate the determination of its optical properties. Here we discuss the basic material and morphological properties of BC aerosols as needed to understand, measure, and calculate their optical properties with a focus on recent progress and remaining gaps in obtaining and using these properties.
For BC aerosols, the complex refractive index outside of the visible spectrum is still poorly constrained, probability distribution functions for parameters of fractal-like shape models and their evolution during atmospheric aging are inadequately defined, and complex refractive indices of atmospheric BC coatings are also insufficiently known. In addition, DDA calculations for coated fractal-like chain aggregates, as needed for modeling the optical properties of atmospheric BC aerosols, are computationally very costly. While such calculations for coated BC particles have made great progress (Liu et al., 2022), extension to size-averaged ensemble calculations with more random realization of morphology types are still needed. These knowledge gaps greatly limit BC radiative transfer evaluation and satellite retrievals. Here, we further outline these knowledge gaps and discuss research efforts needed to fill them.
This work has been supported in part by NSF grant No. OIA-2148788 and NASA ROSES grant 80NSSC20M0205 (PACE SAT Project: PACE UV ROAD).
Reference: Liu, L., G. L. Schuster, H. Moosmüller, S. Stamnes, B. Cairns, and J. Chowdhary (2022). Optical Properties of Morphologically Complex Black Carbon Aerosols: Effects of Coatings. J. Quant. Spectrosc. Radiat. Transfer, 281, 108080 (11 pages), doi.org/ 10.1016/j.jqsrt.2022.108080.