a polarimetric scattering database for non-spherical ice...

A Polarimetric Scattering Database for Non-spherical Ice Particles at Microwave Wavelengths

Zhiyuan Jiang1, Yinghui Lu1,2, Kültegin Aydin1, Johannes Verlinde1, Eugene E. Clothiaux1, and Giovanni Botta1,31The Pennsylvania State University, 2Now at Lawrence Berkeley National Lab, 3Now at Google

Introduction & Motivation

Description of Database

Results from the Database

Summary

Single scattering albedo

Asymmetry parameter

Backscattering cross section

Extinctioncross section

Absorption cross section

Scattering cross section

Amplitudescattering matrices

References:Liu, G., 2008: A database of microwave single-scattering properties for nonspherical ice particles.Bull. Amer. Meteor. Soc., 89, 1563–1570, doi:10.1175/2008BAMS2486.1.

Acknowledgements: We would like to thank Department of Energy (DOE) Atmospheric RadiationMeasurement (ARM) Program for hosting the database. Development of the database wassupported primarily by NSF Grant AGS-128180. Eugene E. Clothiaux’s contributions to the databasewere supported by DOE Grant DE-FG02-05ER64058. The authors would like to acknowledge high-performance computing support from Yellowstone provided by NCAR’s Computational andInformation Systems Laboratory. Portions of this research were conducted with AdvancedCyberInfrastructure computational resources provided by the Institute for CyberScience at ThePennsylvania State University.

Scattering properties of ice particles at microwave frequencies are necessary to• retrieve ice-particle physical properties from radar and radiometer

observations,• evaluate model microphysics by application of forward operators to their

outputs and comparison to observations, and• assimilate active and passive microwave observations in numerical models.Motivated by and complementing previous databases of ice-particle scatteringproperties, we developed a database containing polarimetric single-scatteringproperties of aggregates, branched planar crystals, plates, columns, and conicalgraupel at X- (9.4GHz), Ku- (13.4GHz), Ka- (35.6GHz), W- (94.0GHz) bandwavelengths.

UnitsRange

agg. den. plate column graupel

Incident polar angles

degrees

min 0 0 0 0 0max 180 90 90 90 180inc. 10 10 10 10 10

Incident azimuth anglesmin 0 0 0 0 0max 340 30 30 90 0inc. 20 30 30 10 0

Scattering polar anglesmin 0max 180inc. 1

Scattering azimuth anglesmin 0max 355inc. 5

Database is available at: http://dx.doi.org/10.5439/1258029

Figure 1. Examples of a) an aggregate composed of stellar monomers, b) anaggregate composed of column monomers, c) a branched planar crystal, d) aplate, e) a column and f) a conical graupel particle.

Table 2. Matrix of incident and scattered radiation directions for scattering property calculations of different types of ice particles.

Table 1. Scattering properties stored in the database.

A function of incident directionA function of incident & scattered direction

Polarization dependent

Figure 2. Database branched planar crystal (a1,b1) scattering cross sections, (a2,b2)backscattering cross sections and (a3,b3) asymmetry parameters for incident h-polarizedradiation versus size parameter 2πre/λ, where λ is the wavelength of the incidentradiation and re is the radius of a solid (0.917 g/cm

3) ice sphere with mass equal to that ofthe crystal. The solid lines represent the results for (blue) sector snowflakes and (red)dendrite snowflakes from Liu (2008).

Figure 3.a) Morphology of a branched planar example crystal in the database.b) The phase function p (grey dots) of the example crystal as a function of scattering polarangle θsca for incident radiation with θp

inc=60º and ϕpinc=0º; for each scattering polar angle

θsca there are 72 grey dots, representing values for each of the 72 different scatteringazimuth angles ϕsca. The phase function averaged over the 72 values of ϕsca isrepresented by the solid red line. The dashed red and blue lines represent the phasefunctions of the sector snowflake and dendrite snowflake from Liu (2008) with a similarmaximum dimension.c) The phase function p of the example crystal for (blue) θsca=60º and (red) θsca=120º as afunction of scattering azimuth angle ϕsca for incident radiation with θp

inc=60º and ϕpinc=0º.

d) The phase functions p (averaged over scattering azimuth angle ϕsca) of the examplecrystal as a function of scattering polar angle θsca for radiation with incident polar anglesθp

inc=0º, 30º, 60º, and 90º and with incident azimuth angle ϕpinc=0º. The scattering results

were obtained at the W-band wavelength.

A database of single-scattering properties of ice particles at millimeter tocentimeter wavelengths is presented. Branched planar crystals, plates, columns,aggregates, and conical graupel are generated and their single-scattering propertiescalculated. In addition to the scattering properties of each ice particle, includingtheir amplitude scattering matrices as a function of incident and scattereddirections that provide full polarization information, the database also contains thephysical properties of each ice particle, including the location of each ice particlecomponent, together with imagery of it.

Total number

Aggregates: 660

Branched planars: 405

Plates: 44

Columns: 30

Graupel: 640

Detailed physical properties of each ice particle are stored in the database.

Incident and Scattered Directions

x x

z z

y y

x x x xy y y y

z z z z

a) b)

c) f)e)d)

Manuscript is available at: http://www.atmos-meas-tech-discuss.net/amt-2016-228/#discussion