Version 3: Models for Polar and Geostationary Imagers

Ice cloud bulk single-scattering property models are now available for 35 imagers (just added 4 more on April 30, 2012) from both polar-orbiting and geostationary platforms. This 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. The models are based on the assumption of severely roughened particles.

We are providing these models so that ice cloud properties can be obtained more consistently from various imagers, which should in turn help scientists assess products during sensor comparison least the ice cloud products can be based on ice models built consistently from sensor to sensor.

The files are in NetCDF format, with a single file per imager. The properties are developed first for a set of discrete wavelengths (i.e., spectral models); subsequently the imager band-averaged single-scattering properties are obtained through integration over each imager's spectral response functions (SRF), also called radiance spectral response (RSR) functions.

Properties are provided for each imager band as a function of imager channel and effective diameter, and includes the asymmetry parameter, single-scattering albedo, scattering phase function at 498 angles (also provided), the average ice water content inferred from idealized habits and the microphysical data used to generate the models (provided for eneral information), and the extinction coefficient (β) divided by the IWC. The person who asked me to include this parameter has since retired, but perhaps someone else will find it useful. To help me keep organized, an average wavenumber is provided for each channel - this may be slightly different from the central wavenumber you may be used to stating, but is simply derived from taking an average of the wavelengths for each of the spectral models employed i n the development of the band averaged models.

Because the particle scattering properties are based on severe surface roughening, the phase functions will be much s moother (e.g., no haloes) and the asymmetry parameters will be lower in the shortwave region than those based on smooth-faceted particles. We anticipate that if shortwave channels are used to infer optical thickness and effective radius/diameter, the optical thicknesses based on these roughened particles will be lower and the effective radius/diameter will be larger than if smooth particles are assumed.

This list can be expanded to other sensors by request, but it may take a bit of time. For me to build additional models, you will need to provide me with the response functions for each band. Thanks to Richard Siddans (Rutherford Appleton Lab), we now have the response functions for ATSR-1/2 and AATSR, enabling me to build models for these sensors. MISR is now included too.

The AVHRR imagers on NOAA 4-8 and NOAA 10 have 4 channels, while those on NOAA 9 and NOAA 11-14 have 5 channels; the AVHRR imagers on NOAA 15-19 and MetOp-A/B have 6 channels.

The imager models are combined in a tar file - for access to the compressed (gzip) tar file, click on the "Download Models" button at the top of the page.

The version number of the models (currently at 3.5) and the creation date are in the NetCDF files. The tar file is about 10 MB and has the date of its creation in the filename so you can always find out if y ou have the current models. Note that if you pulled over this file before April 30, 2012, it will not have the most up-to-date listing.

Important note: The availability of these models does not in any way imply that they might be used operationally by one team or another. The models used for MODIS C6 are different from those offered here.

Polar-orbiting imagers: AVHRR on MetOp-B AVHRR on MetOp-A AVHRR on NOAA-5 AVHRR on NOAA-6 AVHRR on NOAA-7 AVHRR on NOAA-8 AVHRR on NOAA-9 AVHRR on NOAA-10 AVHRR on NOAA-11 AVHRR on NOAA-12 AVHRR on NOAA-14 AVHRR on NOAA-15 AVHRR on NOAA-16 AVHRR on NOAA-17 AVHRR on NOAA-18 AVHRR on NOAA-19 MODIS on Terra platform MODIS on Aqua platform VIIRS imager on Suomi-NPP platform Imaging Infrared Radiometer on the CALIPSO platform

These 4 imagers were added on April 30, 2012: MISR on the EOS Terra platform AATSR (7 channels) ATSR-1 (4 channels) ATSR-2 (7 channels)

Geostationary imagers: METEO SG-1 METEO SG-2 future GOES-R Advanced Baseline Imager GOES-8 imager GOES-9 imager GOES-10 imager GOES-11 imager GOES-12 imager GOES-13 imager MTSAT-1 MTSAT-2