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Optical Modeling of Single Asian Dust and Marine Air Particles: A Comparison with Geometric Particle Shapes for
Joseph M Conny1, Robert D Willis2, Diana L Ortiz-Montalvo1
1Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD, 20899-8372 U.S.
Journal of Quantitative Spectroscopy & Radiative Transfer
|April 3, 2024
Summary
This study reveals that tetrahedral shapes best approximate the optical properties of atmospheric dust and marine particles. These findings improve aerosol models for remote sensing applications.
Area of Science:
- Atmospheric Science
- Optical Physics
- Geochemistry
Background:
- Accurate representation of atmospheric particle optical properties is crucial for climate modeling and remote sensing.
- Previous studies often used simplified geometric shapes, potentially leading to inaccuracies in aerosol optical models.
Purpose of the Study:
- To compare the optical properties (extinction and backscatter fraction) of various geometric shapes with real atmospheric particles.
- To evaluate the suitability of different shapes for parameterizing aerosol models.
Main Methods:
- Collected Asian dust and marine background air particles at Mauna Loa Observatory.
- Acquired 3D particle representations using focused ion-beam (FIB) tomography and scanning electron microscopy.
- Calculated optical properties using the discrete dipole approximation method for various geometric shapes (ellipsoids, cuboids, pyramids).
Main Results:
- Most geometric shapes underestimated extinction and overestimated backscatter fraction compared to real particles.
- Tetrahedron and triangular pyramid shapes showed the closest optical properties to actual atmospheric particles.
- Particle surface roughness generally decreased backscatter fraction, with larger surface areas of pyramids accounting for enhanced forward scattering.
Conclusions:
- Tetrahedral shapes offer a more accurate representation of atmospheric particle optical properties than simpler shapes like spheres or cubes.
- The use of tetrahedra in aerosol models can simplify parameterization by eliminating the need for aspect ratio distributions.
- Findings contribute to improved accuracy in remote sensing and climate modeling of atmospheric aerosols.
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