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NCEP/NCAR Reanalysis

Data set identifier: NCEP/NCAR Reanalysis

One-line description: NCEP/NCAR Reanalysis Data

Availability in COAPS: On tape.

Detailed description taken from the CDC:

We have added four-digit year filenames as links to the same data as the two-digit year filenames. We will be removing the two-digit year links in March, 1999. The data is the same; it's just a different filename.

The NCEP/NCAR Reanalysis project is using a state-of-the-art analysis/forecast system to perform data assimilation using past data from 1958 to the present. A large subset of this data is available from CDC in its original 4 times daily format and as daily averages.

Please note: If you acquire NCEP Reanalysis data products from CDC, 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-CIRES Climate Diagnostics Center, Boulder, Colorado, from their Web site at http://www.cdc.noaa.gov/ in any documents or publications using these data. We would also appreciate receiving a copy of the relevant publications. This will help CDC to justify keeping the NCEP Reanalysis data set freely available online in the future. Thank you!

Surface Data

Archive parameters: File names are composed of variable abbreviations, level, and year:

(variable).(level).(year).nc
                                                                        Least
Variables on or near the surface:       File            Units           Sig. Digit
----------------------------            ----            -----           ----------
  Air Temperature                       air.sig995      degK             0.1
  Surface lifted index                  lftx.sfc        degK             0.1
  Best (4-layer) lifted index           lftx4.sfc       degK             0.1
  Omega (vertical velocity)             omega.sig995    Pascal/s         0.001
  Potential temperature                 pottmp.sig995   degK             0.1
  Precipitable water                    pr_wtr.eatm     kg/m^2           0.1
  Pressure                              pres.sfc        Pascals         10.0
  Relative humidity                     rhum.sig995     %                1.0
  Sea level pressure                    slp             Pascals         10.0
  U-wind                                uwnd.sig995     m/s              0.1
  V-wind                                vwnd.sig995     m/s              0.1

  Geopotential hgt (time invariant) *   hgt.sfc         m                1.0
  Land-sea mask (time invariant) **     land                             1.0

* = no year in file name
** = no year or level in filename

Note:

These variables are instantaneous values at the reference time.

Spatial coverage:

2.5-degree latitude x 2.5-degree longitude global grid with 144x73 points
90N-90S, 0E-357.5E

Temporal coverage:

1/1/1958 - 12/31/1997 with output every 6 hours
Data for the current year (1998) from the CDAS program is being made available along with the historical data. Files for 1998 contain as many months as are currently available. All variables are available except precipitable water.

Levels:

Surface or near the surface (.995 sigma level)
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

Missing data:

None

Search keywords:
geopotential, height, humidity, index, land, lifted, omega, potential, pressure, relative, sea, temperature, velocity, vertical, wind

Data set format and size:

All data are stored in netCDF files
The data are divided by variable and year into separate files
There are 441 files currently
Files are 30 Mbytes per variable per year
Current total of 13.4 Gbytes for 4xDaily and 3.4 Gbytes for daily averages

Availability and usage restrictions:

Daily averages are available by anonymous FTP from ftp.cdc.noaa.gov in /Datasets/ncep.reanalysis.dailyavgs/surface.
The 4x daily data files are available on tape.
No usage restrictions.

Last updated: 30 Sep 1998