scholarly journals Oriented Ice Crystals: A Single-Scattering Property Database for Applications to Lidar and Optical Phenomenon Simulations

2019 ◽  
Vol 76 (9) ◽  
pp. 2635-2652 ◽  
Author(s):  
Masanori Saito ◽  
Ping Yang
Keyword(s):  
Optical Properties ◽  
Probability Distribution ◽  
Radiative Transfer ◽  
Single Scattering ◽  
Ice Crystals ◽  
Invariant Imbedding ◽  
Maximum Dimension ◽  
Ice Clouds ◽  
Optical Phenomenon ◽  
Tilting Angle

Abstract A database (TAMUoic2019) of the scattering, absorption, and polarization properties of horizontally oriented hexagonal plates (HOPs) and horizontally oriented hexagonal columns (HOCs) at three wavelengths (355, 532, and 1064 nm) is developed for applications to radiative transfer simulations and remote sensing implementations involving oriented ice crystals. The maximum dimension of oriented ice crystals ranges from 50 to 10 000 μm in 165 discrete size bins. The database accounts for 94 incident directions. The single-scattering properties of oriented ice crystals are computed with the physical-geometric optics method (PGOM), which is consistent with the invariant-imbedding T-matrix method for particles with size parameters larger than approximately 100–150. Note that the accuracy of PGOM increases as the size parameter increases. PGOM computes the two-dimensional phase matrix as a function of scattering polar and azimuth angles, and the phase matrix significantly varies with the incident direction. To derive the bulk optical properties of ice clouds for practical radiative transfer applications, the optical properties of individual HOPs and HOCs are averaged over the probability distribution of the tilting angle of oriented ice crystals based on the use of the TAMUoic2019 database. Simulations of lidar signals associated with ice clouds based on the bulk optical properties indicate the importance of the fraction of oriented ice crystals and the probability distribution of the tilting angle. Simulations of optical phenomena caused by oriented ice crystals demonstrate that the computed single-scattering properties of oriented ice crystals are physically rational.

scholarly journals On the Use of Scattering Kernels to Calculate Ice Cloud Bulk Optical Properties

2012 ◽  
Vol 29 (1) ◽  
pp. 50-63 ◽  
Author(s):  
Xiaodong Liu ◽  
Shouguo Ding ◽  
Lei Bi ◽  
Ping Yang
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Size Distribution ◽  
Conventional Method ◽  
Single Scattering ◽  
Ice Crystals ◽  
Efficient Computation ◽  
Ice Clouds ◽  
Ice Cloud ◽  
Bulk Scattering

Abstract Nonspherical ice crystal optical properties are of fundamental importance to atmospheric radiative transfer through an ice cloud and the remote sensing of its properties. In practice, the optical properties of individual ice crystals need to be integrated over particle size distributions to derive the bulk optical properties of ice clouds. Given a particle size distribution represented in terms of size bins, the conventional approach uses the microphysical and optical properties of ice crystals at the bin centers as approximations to the bin-averaged values. However, errors are incurred when the size bins are large. To reduce the potential errors, a kernel technique is utilized to calculate the bulk optical properties of ice clouds by computing the bin-averaged values instead of using the bin-center values. Comparisons between the solutions based on the conventional method and the kernel technique for different numbers of size bins from in situ measurements demonstrate that the results computed from the kernel technique are more accurate. The present study illustrates that, for a given size distribution, 40 or more size bins should be used to calculate the bulk optical properties of ice clouds by the conventional method. Although the accuracy of bulk-scattering properties can be improved by using fine bin resolutions in the single-scattering property computation, the advantage of using a precomputed database of scattering kernels allows efficient computation of ice cloud bulk optical properties without losing the accuracy.

scholarly journals Derivation of physical and optical properties of midlatitude cirrus ice crystals for a size-resolved cloud microphysics model

2016 ◽  
Author(s):  
A. M. Fridlind ◽  
R. Atlas ◽  
B. van Diedenhoven ◽  
J. Um ◽  
G. M. McFarquhar ◽  
...  
Keyword(s):  
Optical Properties ◽  
Asymmetry Parameter ◽  
Near Infrared ◽  
Single Scattering ◽  
Cloud Microphysics ◽  
Single Scattering Albedo ◽  
Ice Crystals ◽  
Projected Area ◽  
Maximum Dimension ◽  
Plate Aspect Ratio

Abstract. Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 μm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by ~ 0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from ~ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution and g are sensitive to assumed ice properties.

scholarly journals Derivation of physical and optical properties of mid-latitude cirrus ice crystals for a size-resolved cloud microphysics model

2016 ◽  
Vol 16 (11) ◽  
pp. 7251-7283 ◽  
Author(s):  
Ann M. Fridlind ◽  
Rachel Atlas ◽  
Bastiaan van Diedenhoven ◽  
Junshik Um ◽  
Greg M. McFarquhar ◽  
...  
Keyword(s):  
Optical Properties ◽  
Asymmetry Parameter ◽  
Near Infrared ◽  
Single Scattering ◽  
Cloud Microphysics ◽  
Single Scattering Albedo ◽  
Ice Crystals ◽  
Projected Area ◽  
Maximum Dimension ◽  
Plate Aspect Ratio

Abstract. Single-crystal images collected in mid-latitude cirrus are analyzed to provide internally consistent ice physical and optical properties for a size-resolved cloud microphysics model, including single-particle mass, projected area, fall speed, capacitance, single-scattering albedo, and asymmetry parameter. Using measurements gathered during two flights through a widespread synoptic cirrus shield, bullet rosettes are found to be the dominant identifiable habit among ice crystals with maximum dimension (Dmax) greater than 100 µm. Properties are therefore first derived for bullet rosettes based on measurements of arm lengths and widths, then for aggregates of bullet rosettes and for unclassified (irregular) crystals. Derived bullet rosette masses are substantially greater than reported in existing literature, whereas measured projected areas are similar or lesser, resulting in factors of 1.5–2 greater fall speeds, and, in the limit of large Dmax, near-infrared single-scattering albedo and asymmetry parameter (g) greater by  ∼  0.2 and 0.05, respectively. A model that includes commonly imaged side plane growth on bullet rosettes exhibits relatively little difference in microphysical and optical properties aside from  ∼ 0.05 increase in mid-visible g primarily attributable to plate aspect ratio. In parcel simulations, ice size distribution, and g are sensitive to assumed ice properties.

scholarly journals Analysis and evaluation of WRF microphysical schemes for deep moist convection over Southeastern South America (SESA) using microwave satellite observations and radiative transfer simulations

2017 ◽  
Author(s):  
Victoria Sol Galligani ◽  
Die Wang ◽  
Milagros Alvarez Imaz ◽  
Paola Salio ◽  
Catherine Prigent
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
South America ◽  
Single Scattering ◽  
Equal Mass ◽  
Systematic Evaluation ◽  
Transfer Model ◽  
Moist Convection ◽  
Variable Nature ◽  
Deep Moist Convection

Abstract. In the present study, three meteorological events of extreme deep moist convection, characteristic of Southeastern South America (SESA), are considered to conduct a systematic evaluation of the microphysical parameterizations available in the Weather Research and Forecasting (WRF) model by undertaking a direct comparison between satellite-based simulated and observed microwave radiances. A research radiative transfer model, the Atmospheric Radiative Transfer Simulator (ARTS), is coupled with WRF under three different microphysical parameterizations (WSM6, WDM6 and Thompson). Since the main difficulty encountered in the characterization of the microwave scattering signal arises from the complex and variable nature of microphysics properties of frozen hydrometeors, the present study further aims at improving the understanding of their optical properties. The bulk optical properties are computed by integrating the single scattering properties of the Liu (2008) DDA single scattering database across the particle size distributions parametrized by the different WRF schemes in a consistent manner, introducing the equal-mass pproach. The equal mass approach consists in describing the optical properties of the WRF snow and graupel hydrometeors with the optical properties of habits in the DDA database whose dimensions might be different (D'max) but whose mass is conserved. The performance of the radiative transfer simulations is evaluated by comparing the simulations with the available coincident microwave observations up to 190 GHz (with observations from TMI, MHS, and SSMI/S) using the Chi-square test. Good greement is obtained with all observations provided special care is taken to represent the scattering properties of the snow and graupel species.

A comprehensive database of the optical properties of irregular aerosol particles for radiative transfer simulations

2021 ◽  
Author(s):  
Masanori Saito ◽  
Ping Yang ◽  
Jiachen Ding ◽  
Xu Liu
Keyword(s):  
Optical Properties ◽  
Radiative Transfer ◽  
Aerosol Particle ◽  
Volcanic Ash ◽  
Aerosol Particles ◽  
Single Scattering ◽  
Dust Aerosol ◽  
Index Of Refraction ◽  
Particle Sizes

AbstractA database (TAMUdust2020) of the optical properties of irregular aerosol particles is developed for applications to radiative transfer simulations involving aerosols, particularly dust and volcanic ash particles. The particle shape model assumes an ensemble of irregular hexahedral geometries to mimic complex aerosol particle shapes in nature. State-of-the-art light scattering computational capabilities are employed to compute the single-scattering properties of these particles for wide ranges of values of the size parameter, the index of refraction, and the degree of sphericity. The database therefore is useful for various radiative transfer applications over a broad spectral region from ultraviolet to infrared. Overall, agreement between simulations and laboratory/in-situ measurements is achieved for the scattering phase matrix and backscattering of various dust aerosol and volcanic ash particles. Radiative transfer simulations of active and passive spaceborne sensor signals for dust plumes with various aerosol optical depths and the effective particle sizes clearly demonstrate the applicability of the database for aerosol studies. In particular, the present database includes, for the first time, robust backscattering of nonspherical particles spanning the entire range of aerosol particle sizes, which shall be useful to appropriately interpret lidar signals related to the physical properties of aerosol plumes. Furthermore, thermal infrared simulations based on in-situ measured refractive indices of dust aerosol particles manifest the effects of the regional variations of aerosol optical properties. This database includes a user-friendly interface to obtain user-customized aerosol single-scattering properties with respect to spectrally dependent complex refractive index, size, and the degree of sphericity.

scholarly journals A Flexible Parameterization for Shortwave and Longwave Optical Properties of Ice Crystals and Derived Bulk Optical Properties for Climate Models

2020 ◽  
Vol 77 (4) ◽  
pp. 1245-1260 ◽  
Author(s):  
Bastiaan van Diedenhoven ◽  
Brian Cairns
Keyword(s):  
Optical Properties ◽  
Aspect Ratio ◽  
Asymmetry Parameter ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Ice Crystals ◽  
Reference Database ◽  
Extinction Efficiency ◽  
Aspect Ratios ◽  
Asymmetry Parameters

Abstract We provide a parameterization of the extinction efficiency, single-scattering albedo, and asymmetry parameter of single ice crystals with any combination of particle volume, projected area, component aspect ratio, and crystal distortion at any wavelength between 0.2 and 100 μm. The parameterization is an extension of the one previously published by van Diedenhoven et al. In addition, the parameterized optical properties are integrated over size distributions yielding bulk extinction efficiencies, single-scattering albedos, and asymmetry parameters for large ranges of effective radii, particle component aspect ratios, and crystal distortion values. The parameterization of single-particle optical properties is evaluated with a reference database. The bulk optical properties are evaluated against the ice model selected for the Moderate Resolution Imaging Spectroradiometer (MODIS) collection 6 products, for which accurate optical properties are available. Mean absolute errors in parameterized extinction efficiency, asymmetry parameter, and single-scattering albedo are shown to be 0.0272, 0.008 90, and 0.004 68, respectively, for shortwave wavelengths, while they are 0.0641, 0.0368, and 0.0200 in the longwave. Shortwave and longwave asymmetry parameters and single-scattering albedos are shown to vary strongly with particle component aspect ratio and distortion, resulting in substantial variation in shortwave fluxes, but relatively small variations in longwave cloud emissivity. The parameterization and bulk optical properties are made publicly available.

scholarly journals Bulk microphysical properties of semi transparent cirrus from AIRS: a six years global climatology and statistical analysis in synergy with CALIPSO and CloudSat

2011 ◽  
Vol 11 (9) ◽  
pp. 24671-24725
Author(s):  
A. Guignard ◽  
C. J. Stubenrauch ◽  
A. J. Baran ◽  
R. Armante
Keyword(s):  
Statistical Analysis ◽  
General Circulation ◽  
General Circulation Models ◽  
Single Scattering ◽  
Ice Crystals ◽  
Effective Diameter ◽  
Ice Crystal ◽  
Ice Clouds ◽  
Microphysical Properties ◽  
Ice Water

Abstract. This article presents a retrieval method and a statistical analysis of the bulk micropysical properties of semi-transparent ice clouds using the Atmospheric Infrared Sounder (AIRS). Global and long-term coverage provides information on the effective diameter (De) and habits of ice crystals in relation with their environment, ice water path (IWP) and temperature. The method relies on spectral absorption differences between 8 and 12 μm that depend on ice crystal properties. Using single scattering properties for column-like or aggregate-like ice crystals, the method is sensitive to De of up to 85 μm and IWP of up to 120 g m−2. Uncertainties due to the hypotheses on atmospheric parameters and ice crystal single scattering properties as well as horizontal heterogeneities have been demonstrated to be small. The behaviour of bulk microphysical properties as a function of temperature demonstrates that pure ice clouds only occur when Tcld<230 K. On a global scale, these clouds represent practically 25 % of all high clouds and are mainly encountered in the mid-latitudes during winter and in the tropics. Colocated Radar-Lidar Geometrical Profiling (GEOPROF) data reveal an increase in the vertical extent of these cloud layers during mid-latitude winter but which does not significantly impact ice crystal characteristics. A comparative study with bulk microphysical properties from the TIROS-N Operational Vertical Sounder (TOVS) reveals improvements, especially for optically thin and thick semi-transparent ice clouds. Finally, we investigated parametrizations of De as a function of IWP or Ice Water Content (IWC), which could be useful for modelling cirrus in General Circulation Models.

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