PLEASE NOTE: This program is no longer active and has been archived in SSEC Research History as of 6/5/18: More info

Version 3: Ice Cloud Bulk Single-Scattering Property Spectral Models From the Ultraviolet through the Far-Infrared

Ice cloud bulk single-scattering properties are now available at 445 individual wavelengths ranging from 0.2 to 100 µm. The models assume that the ice particles are severely roughened and randomly oriented. Spectral models are available both with and without the full phase matrix based on three habit assumptions as follows.

(1) One set of models is based on a general habit mixture (GHM) involving a set of 9 habits: solid/hollow bullet rosettes, solid/hollow columns, plates, droxtals, small/large aggregate of plates, and an aggregate of solid columns.

(2) Another set of models assumes the use of severely roughened solid columns. This is the habit adopted to date by the CERES team, but our models assume severe roughening. One should assume that these models will be different from the models used by CERES and should contact Pat Minnis at NASA Langley Research Center for more information regarding the operational CERES ice models.

(3) A third set of models is based on the severely roughened aggregate of solid columns, the same particle adopted for use in MODIS Collection 6 products. While the spectral models are based on the same habit, they may not be identical to those used in MODIS operations. For more information and access to the models used for MODIS Collection 6 products, contact Steve Platnick at NASA Goddard Space Flight Center.

There is a single file for each habit assumption as noted above; each file is in NetCDF format and contains the 445 individual spectral models.

If you want properties at a different wavelength than what is provided, you can simply interpolate between two wavelengths to get them.

The single-scattering properties are a function of effective diameter ranging from 10 µm to 120 µm in increments of 5 µm for a total of 23 values. Properties include the asymmetry parameter, single-scattering albedo, extinction efficiency, and the 6 components of the full phase matrix, each at 498 angles (also provided). The phase matrix includes P11, -P12/P11, P22/P11, P33/P11, P43/P11, and P44/P11. The models include total volume and total projected area as a function of effective diameter.

The average ice water content as a function of effective diameter is included for general information; this was inferred from the idealized habits and the microphysical data used to generate the models. By request, we also include the extinction coefficient (β) divided by the IWC, which may be of interest to modelers.

Access to the Models:

The "Download Models" button at the top of the page provides access to the models. Note that there is a new system in place at SSEC and we now ask that you register before downloading data - all we ask for is your name and email address. Since there will be updates in the future, we hope that you will permit us to include you on an email list so that we can send a brief note with what has changed in each subsequent version. So when you register, there will be a box that asks you whether you want to be on an email list - it is voluntary on your part.

Documentation of the Models:

The microphysical data are documented in Heymsfield et al. (2013). The derivation of single scattering properties for individual ice habits from 0.2 to 100 µm is discussed in Yang et al. (2013). The derivation of ice cloud bulk optical property models from 0.2 to 100 µm is discussed in Baum et al. (2014), although an earlier paper (Baum et al. 2011) describes more limited progress on this topic.

Heymsfield, A. J., C. Schmitt, and A. Bansemer, 2013: Ice cloud particle size distributions and pressure dependent terminal velocities from in situ observations at temperatures from 0˚ to -86˚C. J. Atmos. Sci., 70, 4123-4154.

Yang, P., L. Bi, B. A. Baum, K.-N. Liou, G. Kattawar, and M. Mishchenko, 2013: Spectrally consistent scattering, absorption, and polarization properties of atmospheric ice crystals at wavelengths from 0.2 µm to 100 µm. J. Atmos. Sci., 70, 330-347.

Baum, B. A., P. Yang, A. J. Heymsfield, A. Bansemer, A. Merrelli, C. Schmitt, and C. Wang, 2014: Ice cloud bulk single-scattering property models with the full phase matrix at wavelengths from 0.2 to 100 µm. Submitted to J. Quant. Spectrosc. Radiant. Transfer, Special Issue ELS-XIV.

Baum, B. A., P. Yang, A. J. Heymsfield, C. Schmitt, Y. Xie, A. Bansemer, Y. X. Hu, and Z. Zhang, 2011: Improvements to shortwave bulk scattering and absorption models for the remote sensing of ice clouds. J. Appl. Meteor. Clim., 50, 1037-1056.

Note: if you have questions or find problems, please let me know (send email to Bryan Baum) so I can look into the issue. If there is a problem, I want to get it fixed.