HR: 0800h
AN: A51A-0739    [Abstracts]
TI: Parameterization of radiative properties of cirrus clouds
AU: Zhang, Z
EM: zzbatmos@tamu.edu
AF: Department of Atmospheric Sciences, Texas A&M University, TAMU 3150,Texas A&M University, college station, TX 77843 United States
AU: * Yang, P
EM: pyang@ariel.met.tamu.edu
AF: Department of Atmospheric Sciences, Texas A&M University, TAMU 3150,Texas A&M University, college station, TX 77843 United States
AU: Baum, B
AF: NASA Langley Research Center, NASA Langley Research Center, Hampton, VA 23681 United States
AU: Heymsfield, A
AF: National Center for Atmospheric Research, National Center for Atmospheric Research, Boulder, CO 80307 United States
AU: Hu, Y
AF: NASA Langley Research Center, NASA Langley Research Center, Hampton, VA 23681 United States
AB: The goal of this work is to parameterize the bulk scattering properties of ice clouds in the spectral range from 0.2 to 99 microns, that is, from the ultraviolet to the far-infrared. To this end, a database has been developed of single scattering properties for six ice crystal habits (hexagonal solid and hollow columns, aggregates, plates, three-dimensional bullet rosettes, and droxtals). For ice crystals with size parameters smaller than 15, the scattering properties are computed by using the finite-difference time domain method. For larger ice crystals, the composite method is used, and is based on a combination of an improved geometric optics method and an equivalent Lorenz-Mie solution. Ice crystal habit mixtures are determined from analysis of in situ data obtained from several field campaigns. The in situ data consist of particle size distributions, ice water content, and median mass diameter. Instead of using a fixed habit mixture for all the size distributions obtained from in situ sampling, a habit mixture is determined for each size distribution to minimize differences between the calculated (from ice crystal models) and inferred (from in situ measurements) ice water content and median mass diameter values. Based on the inferred habit mixtures, a mean habit mixture ratio is formed. We will show that the statistical scattering properties of the habit mixture ratios for mid-latitude cirrus (FIRE-I, FIRE-II, and ARM IOP) are quite different from the ice clouds sampled during polar and tropical region field campaigns. Based upon these mixture ratio distributions and the single scattering property database, the radiative properties of ice clouds are parameterized as functions of effective size, ice water content and spectral band. Furthermore, the parameterization is implemented in several radiative transfer schemes commonly used in climate models.
DE: 0320 Cloud physics and chemistry
DE: 0360 Transmission and scattering of radiation
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting