A number of datasets which provide observation data and/or background atmospheric estimates for WRFDA can be downloaded directly from the CISL Research Data Archive (RDA) web site. This page lists several useful datasets from that archive, as well as some other useful data sources. All data sets listed on this page are free for users to download.

CISL RDA Background datasets

These data sets can be used with the WRF Pre-processing System to generate first guess (background) files for use in WRFDA.
The details of each dataset (domain, timespan, etc.) may change, click the links to see the most up-to-date descriptions of each dataset.

• NCEP Final Analysis (FNL from GFS) (ds083.2)
  • 1 degree resolution
  • Global domain
  • Output every 6 hours
  • 1999-07-30 to present
• NCEP/NCAR Reanalysis (ds090.0)
  • 2.5 degree resolution
  • Global domain
  • Output every 6 hours
  • 1948-01-01 to present
• NCEP FNL Operational Model Global Tropospheric Analyses (ds083.0)
  • 2.5 degree resolution
  • Northern hemisphere only
  • Output every 12 hours
  • 1997-04-01 to 2007-06-30
• NCEP Eta/NAM model output (ds609.2)
  • 40 km resolution
  • Eta domain: Only a portion of North America
  • Forecasts initialized every 6 hours
  • 1995-04-30 to 2012-12-31

CISL RDA Observation datasets

The following observation data sets can be directly assimilated with WRFDA:

• NCEP ADP Global Upper Air Observational Weather Data (ds351.0)
  • LITTLE_R format (assimilated through OBSPROC)
  • 1999-09-30 to present
• NCEP ADP Global Upper Air and Surface Weather Observations (ds337.0)
  • Surface (METAR, SHIPS, etc.) and Upper-Air (RAOB, ACARS, etc.) data
  • PREPBUFR format (assimilated directly into WRFDA)
  • 1997-04-30 to present
• NCEP GDAS Satellite Radiance Data (ds735.0)
  • Raw radiance data from several instruments:
    • Atmospheric InfraRed Sounder (AIRS)
    • Advanced Microwave Sounding Unit-A (AMSU-A) and Unit-B (AMSU-B)
    • Advanced Tech Microwave Sounder (ATMS)
    • High resolution InfraRed Sounder-3 (HIRS-3) and 4 (HIRS-4)
    • Infrared Atmospheric Sounding Interferometer (IASI)
    • Microwave Humidity Sounder (MHS)
    • Spinning Enhanced Visible and InfraRed Imager (SEVIRI)
    • Special Sensor Microwave Imager/Sounder (SSMIS)
  • GPS Radio Occultation (GPSRO)
  • WMO BUFR format (assimilated directly into WRFDA utilizing a Radiative Transfer Model)
  • 2004 to present (AMSU-A, AIRS)
  • 2005-10-27 to present (HIRS-4, AIRS)
  • 2015-10-10 to present (ATMS, GPSRO, IASI, MHS, SEVIRI, SSMIS)
  • 2004-12-31 to 2014-06-06 (AMSU-B, HIRS3)
  • Note: This data repository is only a partial set of all data available through GDAS. For more instruments, see the next section.
• NCEP ADP Operational Global Surface Observations (ds351.0) and Upper Air Observations (ds353.4)
  • ADP format (converted to LITTLE_R format using a converter)
  • 1999-09-30 to present

Other radiance datasets

The following observation data sets are not maintained by NCAR groups, but can be assimilated directly by WRFDA without any preprocessing:

• NCEP GDAS HTTP or FTP
• A number of different observation data, including:
  • Raw radiance data from several instruments:
    • Atmospheric InfraRed Sounder (AIRS)
    • Advanced Microwave Sounding Unit-A (AMSU-A) and Unit-B (AMSU-B)
    • High resolution InfraRed Sounder-3 (HIRS-3) and 4 (HIRS-4)
    • Infrared Atmospheric Sounding Interferometer (IASI)
    • Microwave Humidity Sounder (MHS)
    • Spinning Enhanced Visible and Infrared Imager (SEVIRI)
  • Conventional observations are from land, ocean, and upper-air platforms
  • GPS Radio Occultation data
• Radiance observations are in WMO BUFR format (assimilated directly into WRFDA utilizing a Radiative Transfer Model), conventional observations in NCEP PREPBUFR format (also assimilated directly into WRFDA)
• Available online for one year prior to current date. Older data can be accessed through the NOMADS website.
• JAXA GCOM-W1 AMSR2 data (free account required: Sign in/Sign up link, Download link)
  • Observations from the JAXA GCOM-W1 AMSR2 instrument in HDF5 format.
  • Products that can be used in WRFDA are brightness temperature (TBR) and cloud water (CLW)
  • From "Download link" above, click:
    AMSR2 -> YEAR -> YYYY.MM -> L1 -> L1R -> 2 (for TBR)
    AMSR2 -> YEAR -> YYYY.MM -> L2 -> CLW -> 2 (for CLW)
  • See the user's guide for information on how to compile WRFDA with HDF5 support.

Other observation datasets

The following observation data sets require some additional processing before being assimilated with WRFDA:

• Precipitation NCEP/EMC 4KM Gridded Data (GRIB) Stage IV Data
  • 4 km resolution
  • Contiguous United States only
  • GRIB format (converted to a WRFDA-readable ASCII format using a converter)
  • 2002-01-01 to present
  • See relevant section in the User's Guide for instructions on how to assimilate
• MADIS data FTP sites: real-time and archived observations
  • Surface and upper-air data as described at the MADIS website
  • MADIS netCDF format (converted to LITTLE_R using the MADIS2LITTLER converter)
  • 2001-07-01 to present

Other datasets

The NCEP FTP site contains a large amount of realtime and near-realtime data for and output from their various operational models. However, the site is very difficult to navigate, and documentation is scant! There is some useful guidance available at this page.

• NCEP FTP SERVER

• Once you have ADP data on your machine, you can use the script adp_to_little-r.csh (inside the latest FETCH TAR file - after Jan 21, 2004) to convert it to LITTLE_R input format.
  This converter is NOT maintained by the WRFDA group, and is not guaranteed to work properly
• For users with MADIS-formatted data, the WRF Data Assimilation group maintains the MADIS2LITTLER converter.