1 CIMSS/SSEC Effort on the Fast IR Cloudy Forward Model Development A Fast Parameterized Single Layer Infrared Cloudy Forward Model Status and Features Hung-Lung Allen Huang & Colleagues CIMSS/SSEC, Univ. of WI-Madison & Ping Yang, Texas A&M 2 nd Workshop on Advanced High Spectral Resolution Infrared Observations Ravello, Italy May 2004

2 UW Hyperspectral Sounder Simulator & Processor (HSSP) Simulator – Clear, Clouds, and Haze Radiances

3 Computing techniques: FDTD: the finite-difference time- domain method IGOM: Improved geometric optics method SSPM: Stretched scattering potential method Composite method: A combination of FDTD or other method (such as the T-matrix) with the weighted summation of approximate solutions for obtaining the single-scattering properties for small size parameters to large size parameters. Parameterization: Based on the effective size of in-situ particle size distribution Sensitivity study Effective particle size Visible optical thickness Simultaneous retrieval of the optical thickness and effective particle size of cirrus clouds UW HSSP Cloudy Fast Model Development

4 Radiative Transfer Approximation Cloud Reflectivity and Transmittance Parameterization

5 The typical ice crystal habits for tropical (left), midlatitude (middle), and polar (right) cirrus cloud system. Data courtesy of A. Heymsfield and his colleagues (NCAR), S. Warren (University of Washington), and P. Lawson (SPEC). Ice Crystal Habits

6 Ice Crystal Single-Scattering Property Database Shapes of ice crystals Aggregates, solid hexagonal columns, Spheres, Bullet-rosettes, Droxtals, Hollow columns, Plates, and Spheroids Wavelengths: 49 Wavelengths from 3.08 µm to 100 µm Size bins: 38 Size bins from 2 µm to 3100 µm in terms of particle maximum dimension

7 Refractive index(real and imaginary parts) of ice The circles indicate the wavelengths where the scattering computations were carried out.

8 Ice Crystal Single-Scattering Property Computation Methods The finite difference time domain (FDTD) code (Yang and Liou, 1996a, Yang et al. 2000, 2004) for small particles with size parameters up to 20. The T-matrix method (Mishchenko 1989) for small spheroids. A combination of an improved geometric optics method (IGOM) (Yang and Liou, 1996b) and the method of Lorenz-Mie Equivalent spheres (equivalence in volume for plates and hollow columns, or in terms of the ratio of volume to project area for other shapes) for medium to large particle sizes.

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