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NCEP/NCAR Reanalysis 1

We have transitioned the data files from netCDF3 to netCDF4-classic format on Monday Oct 20th, 2014.

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

Spatial Coverage:

  • 2.5 degree latitude x 2.5 degree longitude global grid ( 144x73)
  • 90N - 90S, 0E - 357.5E


  • Tropopaise

Update Schedule:

  • Daily

Note: These variables are instantaneous values at the reference time.

Variable Statistic Level Download File Create Plot/Subset
Air Temperature 4-times Daily Tropopause see list plot
Air Temperature Daily Tropopause see list plot
Air Temperature Monthly Mean Tropopause see list plot
Pressure 4-times Daily Tropopause see list plot
Pressure Daily Tropopause see list plot
Pressure Monthly Mean Tropopause see list plot

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 PSL 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:

  • See individual sections. Data in /Datasets/ncep.reanalysis/, Datasets/ncep.reanalysis.dailyavgs/, /Datasets/ncep.reanalysis.derived/
  • Archive parameters: File names are composed of variable abbreviations and year: (variable).tropp.(year).nc
  • On PSL computers the 4x daily data are in the directory /Datasets/nmc.reanalysis/tropopause.
  • On PSL computers the daily average data are in the directory /Datasets/ncep.reanalysis.dailyavgs/tropopause.

Dataset Format and Size:

  • PSL standard NetCDF most are (packed).
  • All data are stored in netCDF files
  • The data are divided by variable and year into separate files
  • There are 82 files currently
  • Each file is about 31 megabytes.
  • Current total of 2.5 Gbytes for 4xDaily and 628 Mbytes for daily averages

Missing Data:

  • Missing data is flagged with a value of -9.96921e+36f.


  • 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 PSL, 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 PSL, Boulder, Colorado, USA, from their Web site at / in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help PSL 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 Laboratory: Data Management
    325 Broadway
    Boulder, CO 80305-3328