File naming convention

The AIRS product files are named in accordance to the following convention:

AIRS.yyyy.mm.dd.ggg.Lev.productType.vm.m.r.b.GproductionTimeStamp.hdf

Where:

• yyyy = 4 digit year number [2002 – ]
• mm = 2 digit month number [01–12]
• dd = day of month [01–31]
• ggg = granule number [1–240] the “.ggg” only applies to Level 1 and Level 2 data. Level 3 data do not have this field
• Lev = processinglevel[“L1A”,”L1B”,”L1C”,”L2”,or“L3”]
• productType: see Product Type strings in the tables below.
• m.r.b = algorithm version identifier is made up of major version, minor version, release version and build number respectively.
• productionTimeStamp = file creation time stamp. Starts off with a letter G for GES DISC processing facility, followed by yydddhhmmss.
  • yy: year number without century;
  • ddd: day of a year [1–366];
  • hhmmss: hours, minutes and seconds UTC time.

Example of a Level 2 standard file name:

AIRS.2019.01.28.120.L2.RetStd_IR.v7.0.1.0.G20071160428.hdf

The version numbers that appear in the AIRS Product Files are slightly different, depending upon the product due to a staged delivery of processing code to the GES DISC. They are:

• Level 1B AMSU-A and HSB Products: v5.0.0.0
• Level 1B AIRS Products: v5.0.x.0
• Level 1B Calibration Subset Product: v5.0.x.0 is still available. It will be superseded at some point in the future.
• Level 1C: v6.7.2.0
• Level 2 Products:
  • Level 2 IR-Only, AIRS+AMSU and AIRS+AMSU+HSB, standard, support, and cloud-cleared radiance products: v7.0.2.0
  • Level 2 CO2; V5.4.11.0
• Level 3 Products:
  • Level 3 Level 2 IR-Only, AIRS+AMSU and AIRS+AMSU+HSB, standard, and support products: v7.0.3.0
  • Level 3 CO2; V5.9.14.0

CLIMCAPS-Aqua product files follow a slightly different naming convention.  Their naming is consistent with other products for which the NASA Sounder Science Investigator-led Processing Systems (SIPS) are responsible for.  They include the following tokens separated by the delimiter '.':

 <Sounder_SIPS_ID>.<platform>.<inst_ID>.<gran_ID>.<product_granularity>.<granule_number>.<product_type>.<variant>.<version>.<production_location>.<prod_timestamp>.<extension>

Example file name for a CLIMCAPS Level 2 AIRS+AMSU product file:

SNDR.AQUA.AIRS_IM.20160114T2359.m06.g240.L2_CLIMCAPS_RET.std.v02_39.G.201104032757.nc

For further details about file naming for CLIMCAPS products, see the NASA CLIMCAPS L2 Format Definition V2 and NASA CLIMCAPS L3 Format Definition V2.

Level 1 Products

Geolocated and calibrated radiances. Files contain six-minute granules, generally 240 per day, of data (except the calibration subset which is produced once per day). There are level 1B data files from each instrument in the AIRS suite as well as a quality assurance subset for the infrared and visible instruments and the daily calibration subset. Level 1C data include various enhancements. Unlike all routine products, L1C files are only stored for 30 days.

AIRS-team Level 2 Products

Geophysical products (temperature, water vapor, clouds, trace gases). Files contain six-minute granules, generally 240 per day, of data. There are standard, support and cloud cleared radiance files for three instrument combinations.

CLIMCAPS-Aqua Level 2 Products

Geophysical products (temperature, water vapor, clouds, trace gases). Files contain six-minute granules, generally 240 per day, of data. Cloud cleared radiances are provided in separate product files. Both types of files are available with data from either AIRS-only or AIRS+AMSU instruments.

AIRS-team Level 3 Products

Gridded statistical summaries of the AIRS geophysical variables. The Level 3 products are averaged over daily and monthly time spans for each of the three instrument combinations of Level 2 standard and support products.

CLIMCAPS-Aqua Level 3 Products

Gridded statistical summaries of the geophysical variables. The Level 3 products are averaged over daily and monthly time spans for both AIRS-only and AIRS+AMSU Level 2 products. Each of the resulting product types is available with either specific or comprehensive quality control (see the 'Data Organization' section of this document or NASA CLIMCAPS L2 Format Definition V2).

AIRS Near Real Time Products

The AIRS Near Real Time (NRT) products are available for Level-1B, Level-1C and Level-2 and stored on a rolling archive for 7 days. The AIRS NRT products are only produced for the AIRS-Only flavor and the NRT product files are listed by short name in the following table. Access to the AIRS NRT data is free but requires prior user registration. AIRS NRT products are produced by the same core science algorithms as in the routine science data production, but using predicted ephemeris in place of definitive ephemeris and the NRT processing proceeds whether or not the previous or subsequent Level 1B granules are present or whether the forecast surface pressure is present.

The advantage of NRT data is its fast turnaround time, generally available within 3 hours of observations globally. They can be utilized in regional weather forecast models as well as in support of field campaigns. The differences between the AIRS NRT and Routine products are described in a memo:

Note that CLIMCAPS V2 products are not available in NRT because they are dependent on MERRA2, which has a latency of ~1 month. This means CLIMCAPS V2 products are primarily suitable for long term studies of Earth system processes.

AIRS Carbon Dioxide Products

The spatial resolution of the AIRS CO₂ Level 2 products is ~ 90 km x 90 km so the files have dimensions of 15 x 22. The Version 5 CO2 Level 3 files have 2-degree latitude x 2.5-degree longitude grid boxes (dimensions of those files are 91 degrees latitude x 144 degrees longitude). CO₂ products using AIRS-Only are only provided up to February, 2017. CO₂ products using AIRS+AMSU are only provided up to February, 2012.

Aqua AIRS Level 2G Precipitation Estimate

The precipitation estimate from the AIRS Level 2 Support product is combined into one daily “Level 2G” global grid with dimensions (24x1440x720). The short name is “AIRG2SSD” and the filename string is “L2G.Precip_Est.” Every hour is a "layer" in the daily file, and the resulting spatial grid cell size is 0.25 degree (~25 km). Thus the grid size is made to fit TRMM products. Since the AIRS precipitation is retrieved at the AMSU footprint resolution, which is about 45 km at nadir, many cells in this 0.25-deg grid are empty. The data are stored such that the first line is the South Pole. The geolocation information for every hour-layer is also provided in the file. Further information about this product can be found at the GES DISC dataset landing page:

https://search.earthdata.nasa.gov/portal/idn/search?q=airg2ssd&ac=true.