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STAR / SMCD / VIIRS Aerosol Calibration and Validation

VIIRS Aerosol Granule Visualization

The VIIRS Aerosol Granule Visualization tool plots single-granule aerosol data in HDF5 format. It is written in the Interactive Data Language (IDL).

The tool can display, for a single VIIRS granule, the

  • aerosol Environmental Data Record (EDR) ( optical thickness at 550 nm and at VIIRS M bands, Angstrom exponent, suspended matter )
  • aerosol Intermediate Product (IP) ( optical thickness at 550 nm, Angstrom exponent, aerosol model, small- and large-mode aerosol models over ocean and their fraction )
  • geometry ( zenith angles, azimuth angles, scattering angle, surface height )
  • VIIRS Sensor Data Record (SDR) ( RGB true color image, radiances and reflectances in 16 VIIRS M bands )
  • VIIRS Cloud Mask (VCM) IP ( cloud detection confidence, cloud shadow, cloud adjecency, fire, sun glint, snow/ice, quality flags, results of various cloud detection tests, etc. )
  • associated quality flags.

Plots of EDR and IP data filtered by their corresponding quality flags can also be plotted in "Combination Plots".


Current IDPS version is 1.0.1, released 09/17/2014.

Version History

Version 1.0.1: Released 09/17/2014.

  • Bugfix: Starting times in the granule selection menu are displayed incorrectly when more than one granule for a given day is present.

Version 1.0: Released 09/03/2014.

  • Initial release

Current Enterprise version is 1.0.1, released 07/01/2021.

Version History

Version 1.0.1: Released 07/01/2021.

  • Bugfix: Allow the granule after year 2020 to be displayed.
  • Handle the change of AOD overall quality flag: [no retrieval, low, medium, high] before 02/13/2018 16:09:01 UTC; [high, medium, low, no retrieval] afterward.

Version 1.0: Released 09/12/2017.

  • Initial release

Current ABI version is 1.0, released 09/12/2017.

Version History

Version 1.0: Released 09/12/2017.

  • Initial release: check readme file for the granule selection and data preparation (different from the IDPS version)


IDL 8.2 or above must be installed. A valid IDL licence is required for compiling the source codes. To use the IDL binary save (.sav) file the IDL Virtual Machine (IDL VM) is needed. The IDL VM is a runtime version of IDL that can execute IDL '.sav' files, but it does not require a license to run, so it is free to use. (See the Exelis site for more information.)

The tool has been tested on Windows (Vista, Win 7) and Linux platforms.


Extract the contents of the downloaded .zip archive file into a directory of your choice.

Extraction from the IDL source code archive file ( results in the following files:,,,,,,, viirs_aer_data.h, viirs_aer_granule.h, color_curve.dat.

Extraction from the IDL binary save file archive file ( produces the following files:

    viirs_aer_granule-32.sav, viirs_aer_granule-64.sav, color_curve.dat

In addition to the source/save files the folder DATA is also created. The DATA folder contains the subfolder 2014198 that has the aerosol EDR (VAOOO...) file and the corresponding geolocation (GAERO...) file for a VIIRS granule with start time 12:01:39 UTC on July 17 (day 198), 2014.

Tool Execution

    NOTE: Before you can display a particular VIIRS aerosol granule files corresponding to that granule must be made available to the tool. VIIRS aerosol granule data can be obtained from NOAA CLASS. The pages EDR Data Access and IP Data Access provides instructions for downloading data from CLASS. As a minimum, the aerosol EDR file (VAOOO) and the geolocation file (GAERO) must be downloaded.

    The VIIRS aerosol granule files should be placed inside the DATA folder. In the DATA folder create a subfolder with the name YYYYDDD, where YYYY is the four-digit year, DDD is the three-digit day of year of the granule (for example, YYYYDDD=2013252 for 9/9/2013), and place the files there. (The supplied sample subfolder has two files, the aerosol EDR (VAOOO) file and the corresponding geolocation (GAERO) file, for a VIIRS granule with start time 12:01:39 UTC on July 17 (day 198), 2014. These files allow you to test the installation and a limited exploration of the tool. With these files you can display only the EDRs, associated quality flags and geometries.)

If you are using the IDL source code:

  1. Start IDL.
  2. Change directory to where you have placed the source codes of the VIIRS aerosol visualization tool.
  3. Type viirs_aer_granule at the IDL prompt to start the visualization tool.

If you are using the IDL binary save file:

  1. Depending on whether your have a 32-bit or a 64-bit platform rename the file viirs_aer_granule.sav.32 or viirs_aer_granule.sav.64, respectively, to viirs_aer_granule.sav
  2. Click (or double-click) on the .sav file (Windows and Macintosh), or start the IDL Virtual Machine (VM). On Windows, select Start > Programs > IDL x.x > (Tools >) IDL Virtual Machine. On UNIX, enter idl -vm at the UNIX command line.
  3. If in step 2 you started the IDL VM navigate to the folder where the IDL binary save file viirs_aer_granule.sav resides, select it and click OK.

  • After the IDL display window appears, select a granule from the menu Granule->Select. Choose the Year, Month, Day and Starting Time, and click the Submit button. An image of the 550nm AOT EDR will be displayed by default.
  • To display a different parameter, select it from the Display drop-down menu.
  • You can change the color of the image, continent lines, missing value and the data range from the Options menu.
  • The current display can be saved into an image file by selecting the menu item File->Save as... and choosing an image format.
  • By selecting the menu item Values->Show Values and by clicking inside the image you can display, in the window Pixel Retrieval Values, the values for a large number of parameters for the pixel selected by clicking inside the image. Information displayed in this window updates when a different pixel in the image is clicked on. The information shown in the Pixel Retrieval Values window can be saved to an ASCII file by selecting Save->To Ascii File menu item in the Pixel Retrieval Values window.
  • To terminate the tool select File->Quit.


To report bugs please contact the author, Dr. Hongqing Liu.