On this page: Temporal Coverage | Spatial Coverage | Levels | Update Schedule | Download/Plot Data | Analysis Tools
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, 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
• These variables are instantaneous values at the reference time.

Spatial Coverage:

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

Levels:

• 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

Update Schedule:

• Daily

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
Pressure	Daily	surface	see list
Pressure	Monthly Mean	surface	pres.mon.mean.nc
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
U-wind	Daily	sig995	see list
U-wind	Monthly Mean	sig995	uwnd.mon.mean.nc
V-wind	4-times Daily	sig995	see list
V-wind	Daily	sig995	see list
V-wind	Monthly Mean	sig995	vwnd.mon.mean.nc
Geopotential hgt	time invariant	Surface	hgt.sfc.nc
Land-sea mask	time invariant	Surface	land.nc

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.

Caveats:

• Please read the problem list before using the data.

Related File Naming & Structure Information:

File Names:

Archive parameters: File names are composed of variable abbreviations, level, and year: (variable).(level).(year).nc

b

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 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:

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

Citation:

• 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 https://psl.noaa.gov/ 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!

References:

• March, 1996 BAMS

Original Source:

• NOAA National Center for Environmental Prediction

Contact:

• Physical Sciences Laboratory: Data Management
  NOAA/ESRL/PSL
  325 Broadway
  Boulder, CO 80305-3328
  psl.data@noaa.gov