Accurate simulation of the optical properties of atmospheric ice crystals with the invariant imbedding T-matrix method

Bi, Lei; Yang, Ping

doi:10.1016/j.jqsrt.2014.01.013

Cited by 173 publications

(112 citation statements)

References 68 publications

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“…One possible method to facilitate such a study is the shape matrix method by Petrov et al (2006), which allows relatively fast computations for different refractive indices and sizes, once the shape-dependent shape matrix has been solved. Another suitable recent development is the invariant imbedding T-matrix method, which allows for fast optical calculations of various scatterers, such as ice crystals and dust particles (Bi and Yang, 2014). Additionally, it would be tremendously helpful to be able to predict scattering errors from model shape differences.…”

Section: Discussionmentioning

confidence: 99%

Retrieving microphysical properties of dust-like particles using ellipsoids: the case of refractive index

et al. 2015

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Abstract. Distributions of ellipsoids are often used to simulate the optical properties of non-ellipsoidal atmospheric particles, such as dust. In this work, the applicability of ellipsoids for retrieving the refractive index of dust-like target model particles from scattering data is investigated. This is a pure modeling study, in which stereogrammetrically retrieved model dust shapes are used as targets. The primary objective is to study whether the refractive index of these target particles can be inverted from their scattering matrices using ellipsoidal model particles. To achieve this, first scattering matrices for the target model particles with known refractive indices are computed. First, a non-negative least squares fitting is performed, individually for each scattering matrix element, for 46 differently shaped ellipsoids by using different assumed refractive indices. Then, the fitting error is evaluated to establish whether the ellipsoid ensemble best matches the target scattering matrix elements when the correct refractive index is assumed. Second, we test whether the ellipsoids best match the target data with the correct refractive index, when a predefined (uniform) shape distribution for ellipsoids is assumed, instead of optimizing the shape distribution separately for each tested refractive index. The results show not only that for both of these approaches using ellipsoids with the true refractive index produces good results but also that for each scattering matrix element even better results are acquired by using wrong refractive indices. In addition, the best agreement is obtained for different scattering matrix elements using different refractive indices. The findings imply that retrieval of refractive index of non-ellipsoidal particles whose single-scattering properties have been modeled with ellipsoids may not be reliable. Furthermore, it is demonstrated that the differences in single-scattering albedo and asymmetry parameter between the best-match ellipsoid ensemble and the target particles may give rise to major differences in simulated aerosol radiative effects.

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Section: Discussionmentioning

confidence: 99%

Retrieving microphysical properties of dust-like particles using ellipsoids: the case of refractive index

et al. 2015

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“…(b) Orientation of the scattered radiation, and hence the scattering plane, in the scattering coordinate system. particle orientations is use of the invariant embedding (Johnson, 1988;Bi and Yang, 2014) or superposition (Mackowski and Mishchenko, 1996;Mackowski, 2014) T-matrix methods. In these approaches the T-matrix for an ice particle can be computed once and then used to calculate efficiently the single-scattering properties averaged over a range of iceparticle orientations.…”

Section: Conical Graupelmentioning

confidence: 99%

“…Examples of numerical methods capable of calculating singlescattering properties of ice particles with arbitrary shapes are the discrete dipole approximation (DDA; Purcell and Pennypacker, 1973;Draine and Flatau, 1994;Yurkin and Hoekstra, 2011), the finite-difference time domain method (FDTD; Yee, 1966;Tavlove and Hagness, 2005), the pseudo-spectral time domain method (Liu et al, 2012), the generalized multiparticle Mie method (GMM; Xu, 1995), and the recently developed invariant embedding (Bi and Yang, 2014) and superposition (Mackowski and Mishchenko, 1996;Mackowski, 2014) T-matrix methods. Though accurate, these methods are often computationally expensive and are not yet practical in running online calculations.…”

Section: Introductionmentioning

confidence: 99%

A polarimetric scattering database for non-spherical ice particles at microwave wavelengths

Jiang

Aydin

et al. 2016

Atmos. Meas. Tech.

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Abstract. The atmospheric science community has entered a period in which electromagnetic scattering properties at microwave frequencies of realistically constructed ice particles are necessary for making progress on a number of fronts. One front includes retrieval of ice-particle properties and signatures from ground-based, airborne, and satellite-based radar and radiometer observations. Another front is evaluation of model microphysics by application of forward operators to their outputs and comparison to observations during case study periods. Yet a third front is data assimilation, where again forward operators are applied to databases of ice-particle scattering properties and the results compared to observations, with their differences leading to corrections of the model state.Over the past decade investigators have developed databases of ice-particle scattering properties at microwave frequencies and made them openly available. Motivated by and complementing these earlier efforts, a database containing polarimetric single-scattering properties of various types of ice particles at millimeter to centimeter wavelengths is presented. While the database presented here contains only single-scattering properties of ice particles in a fixed orientation, ice-particle scattering properties are computed for many different directions of the radiation incident on them. These results are useful for understanding the dependence of iceparticle scattering properties on ice-particle orientation with respect to the incident radiation. For ice particles that are small compared to the wavelength, the number of incident directions of the radiation is sufficient to compute reasonable estimates of their (randomly) orientation-averaged scattering properties.This database is complementary to earlier ones in that it contains complete (polarimetric) scattering property information for each ice particle -44 plates, 30 columns, 405 branched planar crystals, 660 aggregates, and 640 conical graupel -and direction of incident radiation but is limited to four frequencies (X-, Ku-, Ka-, and W-bands), does not include temperature dependencies of the single-scattering properties, and does not include scattering properties averaged over randomly oriented ice particles. Rules for constructing the morphologies of ice particles from one database to the next often differ; consequently, analyses that incorporate all of the different databases will contain the most variability, while illuminating important differences between them. Publication of this database is in support of future analyses of this nature and comes with the hope that doing so helps contribute to the development of a database standard for ice-particle scattering properties, like the NetCDF (Network Common Data Form) CF (Climate and Forecast) or NetCDF CF/Radial metadata conventions.

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“…To compute the scattering phase matrices of these models with specific sizes at CASPOL wavelength, we apply socalled improved geometric optics method (IGOM) for particle with relatively large size and the invariant imbedding T-matrix method (II-TM) for particles with relatively small sizes (Yang and Liou, 1996;Bi et al, 2013;Bi and Yang, 2014;Johnson, 1988). The combination of these two methods is chosen because of the different size parameters of the aerosol and ice crystal populations.…”

Section: Modeling the Depolarization Ratio Of Water Droplets Aerosolmentioning

confidence: 99%

Using depolarization to quantify ice nucleating particle concentrations: a new method

Zenker

Collier

et al. 2017

Atmos. Meas. Tech.

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Abstract. We have developed a new method to determine ice nucleating particle (INP) concentrations observed by the Texas A&M University continuous flow diffusion chamber (CFDC) under a wide range of operating conditions. In this study, we evaluate differences in particle optical properties detected by the Cloud and Aerosol Spectrometer with POLarization (CASPOL) to differentiate between ice crystals, droplets, and aerosols. The depolarization signal from the CASPOL instrument is used to determine the occurrence of water droplet breakthrough (WDBT) conditions in the CFDC. The standard procedure for determining INP concentration is to count all particles that have grown beyond a nominal size cutoff as ice crystals. During WDBT this procedure overestimates INP concentration, because large droplets are miscounted as ice crystals. Here we design a new analysis method based on depolarization ratio that can extend the range of operating conditions of the CFDC. The method agrees reasonably well with the traditional method under non-WDBT conditions with a mean percent error of ±32.1 %. Additionally, a comparison with the Colorado State University CFDC shows that the new analysis method can be used reliably during WDBT conditions.

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Accurate simulation of the optical properties of atmospheric ice crystals with the invariant imbedding T-matrix method

Cited by 173 publications

References 68 publications

Retrieving microphysical properties of dust-like particles using ellipsoids: the case of refractive index

Retrieving microphysical properties of dust-like particles using ellipsoids: the case of refractive index

A polarimetric scattering database for non-spherical ice particles at microwave wavelengths

Using depolarization to quantify ice nucleating particle concentrations: a new method

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