Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 μm

Abstract

A data library is developed containing the scattering, absorption, and polarization properties of ice particles in the spectral range from 0.2 to 100 μm. The properties are computed based on a combination of the Amsterdam discrete dipole approximation (ADDA), the T-matrix method, and the improved geometric optics method (IGOM). The electromagnetic edge effect is incorporated into the extinction and absorption efficiencies computed from the IGOM. A full set of single-scattering properties is provided by considering three-dimensional random orientations for 11 ice crystal habits: droxtals, prolate spheroids, oblate spheroids, solid and hollow columns, compact aggregates composed of eight solid columns, hexagonal plates, small spatial aggregates composed of 5 plates, large spatial aggregates composed of 10 plates, and solid and hollow bullet rosettes. The maximum dimension of each habit ranges from 2 to 10 000 μm in 189 discrete sizes. For each ice crystal habit, three surface roughness conditions (i.e., smooth, moderately roughened, and severely roughened) are considered to account for the surface texture of large particles in the IGOM applicable domain. The data library contains the extinction efficiency, single-scattering albedo, asymmetry parameter, six independent nonzero elements of the phase matrix (P11, P12, P22, P33, P43, and P44), particle projected area, and particle volume to provide the basic single-scattering properties for remote sensing applications and radiative transfer simulations involving ice clouds. Furthermore, a comparison of satellite observations and theoretical simulations for the polarization characteristics of ice clouds demonstrates that ice cloud optical models assuming severely roughened ice crystals significantly outperform their counterparts assuming smooth ice crystals.

G band atmospheric radars: new frontiers in cloud physics

“…Scattering properties of ice particles are now consistently inferred over the electromagnetic spectrum from the ultraviolet through to the far-infrared, whose lower boundary is conventionally assumed at 300 GHz (Yang et al, 2013). Scattering libraries complementary to these are available in the microwave regime (Kim et al, 2007;Hong, 2007b;Liu, 2008a).…”

Dimensions and aspect ratios of natural ice crystals

“…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).…”

“…Since initial work that identified crystal shapes using in situ ob-servations of ice clouds (e.g., Weickmann, 1948, and studies summarized by Dowling and Radke, 1990, and by Heymsfield and McFarquhar, 2002), much effort has been devoted to quantify the microphysical and scattering properties of ice crystals. One important finding is that ambient atmospheric conditions (e.g., temperature and humidity) govern the growth and morphological properties of ice crystals (e.g., aufm Kampe et al, 1951;Lamb and Scott, 1974;Gonda, 1980;Fukuta and Takahashi, 1999;Bacon et al, 2003;Bailey and Hallett, 2002, 2012Korolev et al, 2004) upon which the corresponding scattering properties depend (e.g., Takano and Liou, 1995;Macke et al, 1996;Yang and Liou, 1998;Baran et al, 2001Baran et al, , 2005Yang et al, 2005Yang et al, , 2013Um and McFarquhar, 2007.…”

Photopolarimetric retrievals of snow properties

“…Ice crystals are found to vary within a virtually countless set of shapes, but, limited by the lack of constraints on the correct optical properties, very few studies have departed from the common practice of assuming spherical shapes for the snow grains, an approximation which can negatively impact the quality of the albedo products (Tedesco and Kokhanovsky, 2007;Aoki et al, 2000). Among the available optical models for non-spherical grains are for example those of Baum et al (2011Baum et al ( , 2014 and Yang et al (2013). Incidentally, Räisänen et al (2015) recently attempted to fit measured phase functions of blowing snow by using phase functions of several complex habits provided by Yang et al (2013) in addition to phase functions of other habits.…”