Optical Modeling of Single Asian Dust and Marine Air Particles: A Comparison with Geometric Particle Shapes for Remote Sensing

Conny, Joseph M.; Willis, Robert D.; Ortiz-Montalvo, Diana L.

doi:10.1016/j.jqsrt.2020.107197

i

Optical Modeling of Single Asian Dust and Marine Air Particles: A Comparison with Geometric Particle Shapes for Remote Sensing

2020
By Conny, Joseph M. ; Willis, Robert D. ; Ortiz-Montalvo, Diana L.

Details

Journal Title:

Journal of Quantitative Spectroscopy and Radiative Transfer
Personal Author:

Conny, Joseph M. ; Willis, Robert D. ; Ortiz-Montalvo, Diana L.
NOAA Program & Office:

NOAA General Documents
Description:

We compare the optical properties of various geometric shapes with single atmospheric Asian dust and marine background air particles collected at Mauna Loa Observatory. Three-dimensional representations of the particles were acquired with focused ion-beam (FIB) tomography, which involves FIB milling of individual particles followed by imaging and elemental mapping with scanning electron microscopy. Particles were heterogeneous with mainly dolomite or calcite and a minor amount of iron; marine air particles contained gypsum but no iron. Extinction and backscatter fraction were calculated with the discrete dipole approximation method. Geometric shapes were grouped as ellipsoids (sphere, spheroid, ellipsoid), cuboids (cube, square prism, rectangular prism), and pyramids (tetrahedron, triangular pyramid). Each group represented a progression of shapes with 1, 2, or 3 non-identical axes. Most shapes underestimated particle extinction and overestimated the backscatter fraction. Not surprisingly, extinction and the backscatter fraction of the sphere and cube were furthest from those of the particles. While the 3-axis ellipsoid and rectangular prism were closer dimensionally to the particles, extinction and the backscatter fraction for the 2-axis spheroid and square prism, respectively, were often closer to the particles. The extinction and backscatter fraction for the tetrahedron and triangular pyramid were closer on average to the actual particles than were the other shapes. Tetrahedra have the advantage that parameterization of an aerosol model for remote sensing would not require an aspect ratio distribution. Particle surface roughness invariably decreased the backscatter fraction. While surface roughness typically contributes a minor part to overall scattering, in some cases the larger surface area of the tetrahedron and triangular pyramid sufficiently accounted for enhanced forward scattering of particles from surface roughness.
Keywords:

Atomic And Molecular Physics, And Optics Radiation Spectroscopy Atomic And Molecular Physics, And Optics Atomic And Molecular Physics, And Optics
Source:

Journal of Quantitative Spectroscopy and Radiative Transfer, 254, 107197
DOI:

https://doi.org/10.1016/j.jqsrt.2020.107197
ISSN:

0022-4073
Format:

PDF
Publisher:

Elsevier BV
Document Type:

Journal Article
Rights Information:

Accepted Manuscript
Compliance:

Library
Main Document Checksum:

urn:sha256:59618a1509443078b5aca26246dd35b163959110ebe9ca9589cd07a0466a82e7
Download URL:

https://repository.library.noaa.gov/view/noaa/57629/noaa_57629_DS1.pdf
File Type:

[PDF - 3.12 MB ]

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