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NCEP/NCAR Reanalysis 1: Pressure

We have transitioned the data files from netCDF3 to netCDF4-classic format on Monday Oct 20th. As a result, the files will be compressed instead of being packed with a scale and offset. As with any netCDF4 file, the NetCDF library will perform the uncompression. We expect the files to be read faster, depending on the application you are using. Values may differ slightly because of precision issues. Please let us know if you run into any problems after first reading our netCDF4 doc. We are also changing the time units to use 1800 as the origin year for udunits. This should prove easier for users. The exception to the above are the spectral coefficients files, which are still packed.

Other Grid Types: NCEP Reanalysis Main Page | Pressure Level Data | Surface Data | Surface Flux Data | Other Flux Data |Spectral Coefficents Data | Tropopause Data

Brief Description:

  • NCEP/NCAR Reanalysis 1

Temporal Coverage:

  • 4-times daily, daily and monthly values for 1948/01/01 to present
  • Long term monthly means, derived from data for years 1981 - 2010
  • Values are instantaneous at the time indicated in the files

Spatial Coverage:

  • 2.5 degree x 2.5 degree global grids (144x73)
  • 0.0E to 357.5E, 90.0N to 90.0S


  • 17 Pressure levels (mb): 1000,925,850,700,600,500,400,300,250,200,150,100,70,50,30,20,10
  • Some variables have less: omega (to 100mb) and Humidities (to 300mb).

Update Schedule:

  • Daily

Download/Plot Data:

Variable Statistic Level Download File Create Plot/Subset
Air Temperature 4-times Daily Pressure see list plot
Air Temperature Daily Pressure see list plot
Air Temperature Monthly Mean Pressure air.mon.mean.nc plot
Geopotential Height 4-times Daily Pressure see list plot
Geopotential Height Daily Pressure see list plot
Geopotential Height Monthly Mean Pressure hgt.mon.mean.nc plot
Relative Humidity 4-times Daily Pressure see list plot
Relative Humidity Daily Pressure see list plot
Relative Humidity Monthly Mean Pressure rhum.mon.mean.nc plot
Specific Humidity 4-times Daily Pressure see list plot
Specific Humidity Daily Pressure see list plot
Specific Humidity Monthly Mean Pressure shum.mon.mean.nc plot
Omega (Vertical Velocity) 4-times Daily Pressure see list plot
Omega (Vertical Velocity) Daily Pressure see list plot
Omega (Vertical Velocity) Monthly Mean Pressure omega.mon.mean.nc plot
U-Wind 4-times Daily Pressure see list plot
U-Wind Daily Pressure see list plot
U-Wind Monthly Mean Pressure uwnd.mon.mean.nc plot
V-Wind 4-times Daily Pressure see list plot
V-Wind Daily Pressure see list plot
V-Wind Monthly Mean Pressure vwnd.mon.mean.nc plot


  • Long Term Means are also available here.

  • You can now search the NCEP/NCAR Reanalysis data by selecting one of these links:
    1. Search all of the NCEP/NCAR Reanalysis available at PSD.
    2. Search the NCEP/NCAR Reanalysis 4x daily data available at PSD.
    3. Search the NCEP/NCAR Reanalysis daily average data available at PSD.
    4. Search the PSD products derived from the NCEP/NCAR Reanalysis including monthly and long-term means.
  • Usage Restrictions:

    • None

    Detailed Description:

    • The NCEP/NCAR Reanalysis 1 project is using a state-of-the-art analysis/forecast system to perform data assimilation using past data from 1948 to the present. A large subset of this data is available from PSD in its original 4 times daily format and as daily averages. However, the data from 1948-1957 is a little different, in the regular (non-Gaussian) gridded data. That data was done at 8 times daily in the model, because the inputs available in that era were available at 3Z, 9Z, 15Z, and 21Z, whereas the 4x daily data has been available at 0Z, 6Z, 12Z, and 18Z. These latter times were forecasted and the combined result for this early era is 8x daily. The local ingestion process took only the 0Z, 6Z, 12Z, and 18Z forecasted values, and thus only those were used to make the daily time series and monthly means here.


    Related File Naming & Structure Information:

    File Names:

    • 4-times daily /Datasets/ncep.reanalysis/pressure/var.yyyy.nc
    • Daily data in /Datasets/ncep.reanalysis.dailyavgs/pressure/var.yyyy.nc
    • Monthly mean and climatologies in /Datasets/ncep.reanalysis.derived/pressure/ var.time.stat.nc

    Dataset Format and Size:

    Missing Data:

    • Missing data is flagged with a value of 32767s or 9.36e36f..


    • For dataset source, please cite:Kalnay et al.,The NCEP/NCAR 40-year reanalysis project, Bull. Amer. Meteor. Soc., 77, 437-470, 1996.
    • Please note: If you acquire NCEP Reanalysis data products from PSD, we ask that you acknowledge us in your use of the data. This may be done by including text such as NCEP Reanalysis data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at http://www.esrl.noaa.gov/psd/ in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help PSD to justify keeping the NCEP Reanalysis data set freely available online in the future. Thank you!


    • March, 1996 BAMS

    Original Source:

    • NOAA National Center for Environmental Prediction


    • Physical Sciences Division: Data Management
      325 Broadway
      Boulder, CO 80305-3328