MODIS Version 2 Ice Cloud Scattering Models
These 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. A number of improvements were made to the methodology used for the Version 1 models:
- Size distributions are based on 45 size bins (particle size ranges from 2 to 9500 microns), while the Version 1 models were based on 5 size bins.
- Use of an ice particle habit distribution that varies as a function of maximum dimension.
- New sets of ice crystal scattering properties calculated for a variety of habits, including plates, hollow and solid columns, 3-D bullet rosettes, and aggregates.
- Each model contains the mean and standard deviation of each microphysical and optical property, including ice water content, mean mass diameter, single scatter albedo, asymmetry factor, fraction of delta transmitted energy, extinction efficiency, and the scattering phase function.
In situ Microphysical Ice Cloud Data
More complete descriptions of the in situ data are provided in the following links.
Description of the field experiments and data sources
Particle size distributions
Ice crystal habit "recipe" implemented for these models
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
MODIS Narrowband Models:
A tar file has been prepared for each of the MODIS bands noted below. Each tar file contains a set of 18 models, with effective diameters (De) spanning a range from 10 to 180 microns in increments of 10 microns.
Naming convention of individual files: The band number and effective diameter is in the file name. For example, a file named MODIS_mix1_b06_d080.dat means this: habit mixture 1 as described above, MODIS band 6 (1.6 micron wavelength), and a De of 80 microns.
These new models incorporate a significant update in scattering libraries detailed in Yang et al. (2005), with the full reference below. These new models tend to have a higher asymmetry factor and a lower single scattering albedo than the previous models. The changes in the scattering phase function are minimal. There is no delta transmission energy in these new models, as this is primarily only important at shorter wavelengths. To make these new models distinguishable from the previous ones that we had available prior to 4/10/2006, the file naming convention has been changed so that prefix 'b' for band is now 'ch' for channel. Thus, a file named MODIS_mix1_ch20_d080.dat means this: habit mixture 1 as described above, MODIS channel 20 (3.75 micron wavelength), and a De of 80 microns.