Restrictions | Details | Caveats | File Naming | Citation | References | Original Source | Contact
NCEP/NCAR Reanalysis 1: Spectral CoefficientsWe will be transitioning the data files from netCDF3 to netCDF4-classic format. 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 differe 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 acces to use 1800 as a reference date for udunits. This should prove easier for users.
- NCEP/NCAR Reanalysis 1:Spectral Coefficients from the global analysis model.
- 4-times daily 1948/01/01 to present
- T62 Spectral Coefficients
- 28 Sigma levels: 0.995, 0.9821, 0.9644, 0.9425, 0.9159, 0.8838, 0.8458, 0.8014, 0.7508, 0.6943, 0.6329, 0.5681, 0.5017, 0.4357, 0.372, 0.3125, 0.2582, 0.2101, 0.1682, 0.1326, 0.1028, 0.0782, 0.058, 0.0418, 0.0288, 0.0183, 0.0101, 0.0027
- Some variables not defined at all levels.
Note: These variables are instantaneous values at the reference time.
|Divergence||4-times Daily||28 levels||/Datasets/ncep.reanalysis/spectral/div.spec.yyyy.nc|
|Natural Log of Pressure||4-times Daily||Surface||/Datasets/ncep.reanalysis/spectral/pres.nlog.sfc.yyyy.nc|
|Specific Humidity||4-times Daily||28 levels||/Datasets/ncep.reanalysis/spectral/shum.spec.yyyy.nc|
|Virtual Air Temperature||4-times Daily||28 levels||/Datasets/ncep.reanalysis/spectral/vair.spec.yyyy.nc|
|Relative Vorticity||4-times Daily||28 levels||/Datasets/ncep.reanalysis/spectral/vort.spec.yyyy.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.
- There are no daily averages for the spectral data available from PSD.
- See individual sections. Data in /Datasets/ncep.reanalysis/, Datasets/ncep.reanalysis.dailyavgs/, /Datasets/ncep.reanalysis.derived/
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 205 files currently
- Sizes range from 17 Kbytes to 331 Mbytes per variable per year
- Current total of 54 Gbytes for 4xDaily
- 4x daily data are available from ftp.cdc.noaa.gov in /Datasets/ncep.reanalysis/spectral/.
- The 4x data files are quite large, so you may only be able to download them if you have a fast network connection.
- The FORTRAN code readspec.f may be helpful in converting the coefficients to a regular grid.
- If you would like datasets on a media such as tape, you will need to get them from another institution. NCAR (link) provides such a service for their datasets.
- 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