The models provided through this web page are intended for use in the retrieval of ice cloud properties in the visible (VIS) to shortwave infrared (SWIR) spectral region. The models are provided over the spectral range from 0.4 to 2.2 microns at 0.01 micron resolution. While there are a few spectral gaps, bulk scattering models are available for 144 wavelengths. The difference between this set of models and those provided for specific imagers such as MODIS is that these models are provided at specific wavelengths, whereas those for the imagers have been integrated over each imager channel's spectral response function.
The bulk scattering models are the result of a multiyear team effort to derive new ice cloud scattering models based on reanalysis of in-situ data from a variety of midlatitude and tropical ice cloud field experiments. Here are a few details about the models:
More complete descriptions of the in situ data are provided in the following links.
The percentage of each habit used in the integration of a given property over a particle size distribution is based on the particle's maximum dimension.
D < 60 microns:
60 microns < D < 1000 microns:
15% 3D bullet rosettes
50% solid columns
1000 microns < D < 2500 microns:
45% hollow columns
45% solid columns
2500 microns < D < 9500 microns
97% 3D bullet rosettes
VIS-SWIR Spectral Models:
A set of 18 text files have been prepared, each one specific to a given effective diameter (De). The De span a range from 10 to 180 microns in increments of 10 microns. Each file contains entries for each of the 144 wavelengths for which properties are available. The habit mixture as described above is used for all calculations of microphysical and optical properties.
Each of these files contains the following properties.
Microphysical properties provided once per file as they are not wavelength dependent:
- Ice Water Content (IWC)
- Total ice particle projected area
- Total ice particle volume
- Median mass diameter
Mean and standard deviation of optical properties for each wavelength.
- Asymmetry factor (g)
- Single scattering albedo (omega)
- Extinction efficiency (Qe)
- Scattering cross section (sig_scat)
- Extinction cross section (sig_ext)
Note: the files provided above do NOT contain scattering phase functions (both means and standard deviations). The scattering phase files are provided in a tar file through the link below; a file is available for each individual wavelength within the tar file.
Scattering Phase Functions- tar file
Note: Format of scattering phase function files:
Within each of the (ascii) files, the first line is wavelength; the 2nd line provides column titles. Beginning with the 3rd line, you have the following:
1st column: scattering angle (from 0 to 180 degrees with 498 angles)
2nd column: mean value of scattering phase function at De = 10 microns
3rd column: standard deviation of phase function at De = 10 microns
4th column: mean value of scattering phase function at De = 20 microns
5th column: standard deviation of phase function at De = 20 microns
and so forth for the rest of the De values up to 180 microns
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