Application of modern radiative transfer tools to model laboratory quartz emissivity

Pitman, K. M.; Wolff, Michael; Clayton, Geoffrey C.

doi:10.1029/2005je002428

Cited by 36 publications

(46 citation statements)

References 45 publications

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“…Works in the past have attempted to capture the nonlinear behavior by building light scattering models [ Conel , ; Wald , ; Moersch and Christensen , ; Wald and Salisbury , ; Mustard and Hays , ; Pitman et al , ; Cheng et al , ]. In these works, the complex scattering of light by closely packed particles that are on the order of the wavelength of observed radiation are modeled using a combination of two theories: Mie theory and the theory of radiative transfer (RT).…”

Section: Introductionmentioning

confidence: 99%

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

2017

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Mid‐infrared spectroscopy is a useful tool for remotely sensing the composition of Earth and other planets. Quantitative mineralogical investigations are possible using remotely sensed data; however, the difficulty in modeling complex interactions of light with particles that are on the order of the wavelength limits the usefulness of the remote sensing data. As part of an effort to develop a more effective treatment of light scattering in planetary regolith, we explore the ability of T‐matrix and radiative transfer (RT) hybrid models to produce emissivity spectra that are consistent with laboratory measurements. Parameters obtained from T‐matrix calculations are used in three different RT models to construct emissivity spectra of enstatite particles of different sizes. Compared to the widely used Mie/RT hybrid models, the T‐matrix/RT hybrid models produce more consistent emissivity spectra for the finest particle size fraction (3.3 μm). Overall, T‐matrix hybrid models produce improved emissivity spectra, but larger particle sizes are still difficult to model. The improvement observed in T‐matrix/RT hybrid models is a result of the inclusion of multiple scattering in closely packed media, and it demonstrates the importance of the implementation of physically realistic factors in developing a more effective light scattering model for planetary regolith. Further development and implementation of this and similar hybrid models will result in an improvement in quantitative assessments of planetary particulate surfaces from mid‐infrared spectra.

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Section: Introductionmentioning

confidence: 99%

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

2017

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“…Mustard and Hayes 10 utilized a model similar to the best-performing model of Moersch and Christensen 8 , focusing on the impact of hyperfine particles on their reflectance spectra of quartz. Pittman et al 11 revisited the results of Moersch and Christensen 8 , attempting to improve the match between measurements and model by applying corrections to the Mie scattering computations of the single-particle scattering and extinction properties.…”

Section: Background and Approachmentioning

confidence: 98%

Radiative transfer modeling of surface chemical deposits

Reichardt

Kulp

2016

SPIE Proceedings

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Remote detection of a surface-bound chemical relies on the recognition of a pattern, or "signature," that is distinct from the background. Such signatures are a function of a chemical's fundamental optical properties, but also depend upon its specific morphology. Importantly, the same chemical can exhibit vastly different signatures depending on the size of particles composing the deposit. We present a parameterized model to account for such morphological effects on surface-deposited chemical signatures. This model leverages computational tools developed within the planetary and atmospheric science communities, beginning with T-matrix and ray-tracing approaches for evaluating the scattering and extinction properties of individual particles based on their size and shape, and the complex refractive index of the material itself. These individual-particle properties then serve as input to the Ambartsumian invariant imbedding solution for the reflectance of a particulate surface composed of these particles. The inputs to the model include parameters associated with a functionalized form of the particle size distribution (PSD) as well as parameters associated with the particle packing density and surface roughness. The model is numerically inverted via Sandia's Dakota package, optimizing agreement between modeled and measured reflectance spectra, which we demonstrate on data acquired on five size-selected silica powders over the 4-16 µm wavelength range. Agreements between modeled and measured reflectance spectra are assessed, while the optimized PSDs resulting from the spectral fitting are then compared to PSD data acquired from independent particle size measurements.

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“…Pitman et al 11 consider a hybrid modified-Mie/four-stream discrete ordinate model, treating the closepacking modifications to the Mie scattering via either the forward-peak subtraction used by Wald & Salisbury 16 (1995) or via a statistical static structure factor 27 approach. They report similar difficulties in being able to accurately predict the quartz LWIR spectra across all wavelengths and particle size distributions considered.…”

Section: The State Of Quantitative Predictionsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9][10][11][12] Size dependent spectral variations form the basis for estimating particle size distributions for atmospheric aerosols. 13 Taking into account particle size effects is essential for accurately interpreting the mineralogy of planetary regoliths from remote sensing data, while also allowing characterization of the regolith's physical properties.…”

Section: Introductionmentioning

confidence: 99%

Changes in apparent emissivity as a function of viewing geometry

2011

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We reiterate the fact that the apparent emissivity of a solid surface can depend on not only the composition and particle size distribution comprising the surface but also on view-angle relative to the bulk surface geometry. We report on experiments measuring the longwave infrared emissivity of quartz sand samples sorted by particle size and observed at a series of view angles up to 60 • away from the normal to the bulk sample surface. We show that particle-size and view-angle effects on the apparent emissivity of our quartz samples can mimic each other. In circumstances where significantly off-normal view-angles are unavoidable and characterizing surface qualities are desired, these two effects could be confused. We discuss the existing explanations for these effects. We argue that the view-angle emissivity dependence is intrinsically a bulk geometric effect, not due to a change in apparent particle-size (via coarse grains obscuring finer ones at larger view-angles). We summarize the predominant qualitative explanations of the particle-size effects and review the literature comparing quantitative models and observations. We argue that the existing quantitative models are inadequate for explaining the observations, pointing to a need for further work in this area.

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Application of modern radiative transfer tools to model laboratory quartz emissivity

Cited by 36 publications

References 45 publications

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

T‐matrix and radiative transfer hybrid models for densely packed particulates at mid‐infrared wavelengths

Radiative transfer modeling of surface chemical deposits

Changes in apparent emissivity as a function of viewing geometry

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