Ice particle habit and surface roughness derived from PARASOL polarization measurements

Cole, B. H.; Yang, Ping; Baum, Bryan A.; Riédi, J.; C.‐Labonnote, Laurent

doi:10.5194/acp-14-3739-2014

Cited by 62 publications

(76 citation statements)

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“…Surface roughness is applied only in the IGOM computation (D max > 10 µm). The column aggregate shape is chosen because the most extensive previous study on a global scale (Cole et al, 2014) implies that this habit produces the most consistent agreement with observations. In addition, this habit is used in the retrieval scheme for the operational MODIS Collection 6 cloud products.…”

Section: Selection Of Retrieval Parametersmentioning

confidence: 74%

“…This particle shape is an aggregate of eight column elements that are solid hexagonal particles with slightly different particle aspect ratios (originally defined in Liou, 1996, see Yang et al, 2013, for geometric parameters). A gamma particle size distribution with an effective size (diameter) of 60 µm and an effective variance of 0.1 is used in this study since we expect little impact on our analysis due to this size distribution selection (Cole et al, 2014).…”

Section: Selection Of Retrieval Parametersmentioning

confidence: 99%

“…These measurements have been used to infer both particle habit (Chepfer et al, 1998;C.-Labonnote et al, 2001;Masuda et al, 2002;Knap et al, 2005;Baran and C.-Labonnote, 2007) and surface roughness (Baran and C.-Labonnote, 2006;Cole et al, 2013Cole et al, , 2014. Since polarized reflectivity saturates at relatively small optical thickness (generally about τ = 5, Masuda and Takashima, 1992), the conventional "best-fit" approach to this problem computes the residual sum of squares (RSS) from the multi-angle observations of polarized reflectivity and reflectivity simulations, and selects the ice particle model that minimizes the RSS when τ > 5.…”

Section: Introductionmentioning

confidence: 99%

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Degree of ice particle surface roughness inferred from polarimetric observations

et al. 2016

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Abstract. The degree of surface roughness of ice particles within thick, cold ice clouds is inferred from multidirectional, multi-spectral satellite polarimetric observations over oceans, assuming a column-aggregate particle habit. An improved roughness inference scheme is employed that provides a more noise-resilient roughness estimate than the conventional best-fit approach. The improvements include the introduction of a quantitative roughness parameter based on empirical orthogonal function analysis and proper treatment of polarization due to atmospheric scattering above clouds. A global 1-month data sample supports the use of a severely roughened ice habit to simulate the polarized reflectivity associated with ice clouds over ocean. The density distribution of the roughness parameter inferred from the global 1-month data sample and further analyses of a few case studies demonstrate the significant variability of ice cloud singlescattering properties. However, the present theoretical results do not agree with observations in the tropics. In the extratropics, the roughness parameter is inferred but 74 % of the sample is out of the expected parameter range. Potential improvements are discussed to enhance the depiction of the natural variability on a global scale.

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Section: Selection Of Retrieval Parametersmentioning

confidence: 74%

Section: Selection Of Retrieval Parametersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Degree of ice particle surface roughness inferred from polarimetric observations

et al. 2016

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“…This is because they consist of ice particles with various microphysical characteristics, e.g. a wide range of habits and sizes Forster et al, 2007;Baran et al, 2007;Cole et al, 2014;Yang et al, 2015). Different ice particle habits have varying single-scattering characteristics, resulting in different radiative properties.…”

Section: Introductionmentioning

confidence: 99%

Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission

et al. 2016

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Abstract. In this study, various ice particle habits are investigated in conjunction with inferring the optical properties of ice clouds for use in the Global Change Observation Mission-Climate (GCOM-C) satellite programme. We develop a database of the single-scattering properties of five ice habit models: plates, columns, droxtals, bullet rosettes, and Voronoi. The database is based on the specification of the Second Generation Global Imager (SGLI) sensor on board the GCOM-C satellite, which is scheduled to be launched in 2017 by the Japan Aerospace Exploration Agency. A combination of the finite-difference time-domain method, the geometric optics integral equation technique, and the geometric optics method is applied to compute the single-scattering properties of the selected ice particle habits at 36 wavelengths, from the visible to the infrared spectral regions. This covers the SGLI channels for the size parameter, which is defined as a single-particle radius of an equivalent volume sphere, ranging between 6 and 9000 µm. The database includes the extinction efficiency, absorption efficiency, average geometrical cross section, single-scattering albedo, asymmetry factor, size parameter of a volume-equivalent sphere, maximum distance from the centre of mass, particle volume, and six nonzero elements of the scattering phase matrix. The characteristics of calculated extinction efficiency, single-scattering albedo, and asymmetry factor of the five ice particle habits are compared. Furthermore, sizeintegrated bulk scattering properties for the five ice particle habit models are calculated from the single-scattering database and microphysical data. Using the five ice particle habit models, the optical thickness and spherical albedo of ice clouds are retrieved from the Polarization and Directionality of the Earth's Reflectances-3 (POLDER-3) measurements, recorded on board the Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar (PARASOL) satellite. The optimal ice particle habit for retrieving the SGLI ice cloud properties is investigated by adopting the spherical albedo difference (SAD) method. It is found that the SAD is distributed stably due to the scattering angle increases for bullet rosettes with an effective diameter (D eff ) of 10 µm and Voronoi particles with D eff values of 10, 60, and 100 µm. It is confirmed that the SAD of small bullet-rosette particles and all sizes of Voronoi particles has a low angular dependence, indicating that a combination of the bullet-rosette and Voronoi models is sufficient for retrieval of the ice cloud's spherical albedo and optical thickness as effective habit models for the SGLI Published by Copernicus Publications on behalf of the European Geosciences Union. 12288H. Letu et al.: Investigation of ice particle habits to be used for ice cloud remote sensing sensor. Finally, SAD analysis based on the Voronoi habit model with moderate particle size (D eff = 60 µm) is compared with the conventional general habit mixture mode...

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“…Ice clouds consist almost exclusively of non-spherical ice crystals with various shapes (i.e., habits) and sizes (e.g., Liou, 1986). To determine the influences of ice clouds on solar and infrared radiation as required for numerical models and remote sensing retrievals, knowledge of single-scattering properties of ice crystals is required (e.g., Fu, 1996Fu, , 2007McFarquhar et al, 2002;Baum et al, 2011;Baran, 2012;DeVore et al, 2012;Yang et al, 2013;Yi et al, 2013;Um and McFarquhar, 2013;Cole et al, 2014;van Diedenhoven et al, 2014a).…”

Section: Introductionmentioning

confidence: 99%

Dimensions and aspect ratios of natural ice crystals

McFarquhar

Hong

et al. 2015

Atmos. Chem. Phys.

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Abstract. During the 2006 Tropical Warm Pool InternationalCloud Experiment (TWP-ICE) in the tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPAR-TICUS) campaign at mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures (T ) between −87 and 0 • C. The projected maximum dimension (D ), length (L ), and width (W ) of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured. Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. The dimensions and aspect ratios (AR, the dimension of the major axis divided by the dimension of the minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus.Dimensions of crystals generally increased with temperature. Columns and bullets had larger dimensions (i.e., W ) of the minor axis (i.e., a axis) for a given dimension (i.e., D or L ) of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50 ± 1.35 during three campaigns and 6.32 ± 1.34 (5.46 ± 1.34; 4.95 ± 1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and IS-DAC at −67 < T < −35 • C and at −40 < T < −15 • C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. The L-W relationships of columns derived using current data exhibited a strong dependence on temperature; similar relationships determined in previous studies were within the range of the current data.

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Ice particle habit and surface roughness derived from PARASOL polarization measurements

Cited by 62 publications

References 50 publications

Degree of ice particle surface roughness inferred from polarimetric observations

Degree of ice particle surface roughness inferred from polarimetric observations

Investigation of ice particle habits to be used for ice cloud remote sensing for the GCOM-C satellite mission

Dimensions and aspect ratios of natural ice crystals

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