Restrictions | Details | Caveats | File Naming | Citation | References | Original Source | Contact
NCEP/NCAR Reanalysis 1: Surface
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.
- NCEP/NCAR Reanalysis 1
- 4-times daily, daily and monthly values for 1948/01/01 to present
- Long term monthly means, derived from data for years 1981 - 2010
- These variables are instantaneous values at the reference time.
- 2.5 degree latitude x 2.5 degree longitude global grid (144x73)
- 90N - 90S, 0E - 357.5E
- Surface or near the surface (.995 sigma level), or entire atmosphere (eatm)
- Also, precipitable water is included here, because it is a 3-D file on a 2.5 degree grid, but it is not a surface value, but rather for the entire atmospheric column
|Variable||Statistic||Level||Download File||Create Plot/Subset|
|Air Temperature||4-times Daily||sig995||see list|
|Air Temperature||Daily||sig995||see list|
|Air Temperature||Monthly Mean||sig995||air.mon.mean.nc|
|Surface lifted index||4-times Daily||surface||see list|
|Surface lifted index||Daily||surface||see list|
|Best (4-layer) lifted inde||4-times Daily||surface||see list|
|Best (4-layer) lifted index||Daily||surface||see list|
|Omega (vertical velocity)||4-times Daily||sig995||see list|
|Omega (vertical velocity)||Daily||sig995||see list|
|Potential temperature||4-times Daily||sig995||see list|
|Potential temperature||Daily||sig995||see list|
|Precipitable water||4-times Daily||eatm||see list|
|Precipitable water||Daily||eatm||see list|
|Precipitable water||Monthly Mean||eatm||pr_wtr.mon.mean.nc|
|Pressure||4-times Daily||surface||see list|
|Relative humidity||4-times Daily||sig995||see list|
|Relative humidity||Daily||sig995||see list|
|Relative humidity||Monthly Mean||sig995||rhum.mon.mean.nc|
|Sea level pressure||4-times Daily||sea-lvl||see list|
|Sea level pressure||Daily||sea-lvl||see list|
|Sea level pressure||Monthly Mean||sea-lvl||slp.mon.mean.nc|
|U-wind||4-times Daily||sig995||see list|
|V-wind||4-times Daily||sig995||see list|
|Geopotential hgt||time invariant||Surface||hgt.sfc.nc|
|Land-sea mask||time invariant||Surface||land.nc|
- 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.
- Please read the problem list before using the data.
Archive parameters: File names are composed of variable
abbreviations, level, and year: (variable).(level).(year).nc
Dataset Format and Size:
- PSD 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 450 files currently
- Files are 30 Mbytes per variable per year
- Current total of 13.8 Gbytes for 4xDaily and 3.4 Gbytes for daily averages
- 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
- NOAA National Center for Environmental Prediction
Physical Sciences Division: Data Management
Boulder, CO 80305-3328