NCEP Daily Global Analyses

Brief Description:

• NCEP Daily Global Analyses.

Temporal Coverage:

• Daily mean values 1979/12/01 to present.
• Daily Long Terms means means for years 1985-1996.

Spatial Coverage:

• 2.5 degree latitude x 2.5 degree longitude global grid (144x73).
• 90.0N - 90.S, 0.0E - 357.5E.

Levels:

• Pressure levels at surface, 1000, 850, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50 mb.
• Exceptions: rhum--surface, 1000-300 mb only,hgt--no surface data.

Update Schedule:

• Daily

Download/Plot Data: (FTP Access)

Variable	Statistic	Level	Download File (size)	Create Plot/Subset
Zonal Wind	Daily Mean	Pressure	uwnd.yyyy.nc
Meridional Wind	Daily Mean	Pressure	vwnd.yyyy.nc
Air temperature	Daily Mean	Pressure	air.yyyy.nc
Geopotential Height	Daily Mean	Pressure	hgt.yyyy.nc
Relative Humidity	Daily Mean	Pressure	rhum.yyyy.nc
Sea Level Pressure	Daily Mean	Pressure	slp.yyyy.nc
Surface Pressure	Daily Mean	Surface	srfp.yyyy.nc
Tropopause pressure	Daily Mean	Tropopause	trpp.yyyy.nc
Tropopause temperature	Daily Mean	Tropopause	trpt.yyyy.nc
Precipitable water	Daily Mean	Column	pr_wtr.yyyy.nc

Plus files with .sfc. as the first infix for the surface levels for the variables air, rhum, uwnd, and vwnd.

Variable	Statistic	Level	Download File (size)	Create Plot/Subset
Zonal Wind	Mean	Surface	uwnd.sfc.yyyy.nc	8M
Meridional Wind	Mean	Surface	vwnd.sfc.yyyy.nc	8M
Air Temperature	Mean	Surface	air.sfc.yyyy.nc	8M
Relative Humidity	Mean	Surface	rhum.sfc.yyyy.nc	8M

Usage Restrictions:

• None

Detailed Description:

• NB: The surface levels of the air temperature, relative humidity, u-wind and v-wind pressure level files have been broken out into separate files.
  

   

  NCEP prepares a twice-daily global analysis at 2.5 degrees resolution on pressure levels as a product of their operational forecast system. The original data set as stored at the National Center for Atmospheric Research (NCAR) starts in July 1976 and is being updated continuously at NCAR. We make a subset of this data available beginning in 1979.

   

  As part of a research project supported by the National Science Foundation, the NCEP data has been processed by NCAR into a convenient format for climatological studies. Some quality control and error-checking are done at this time. PSL has processed the twice-daily data by linearly interpolating to fill in missing values and then creating a daily average from the twice daily data.

   

  The data set provided is the (00Z + 12Z)/2. (i.e., analyzed) data. In the analysis process, the observations are interpolated to a grid. Because (1) large parts of the world (and many levels) have no observations and (2) the data are not taken at one time (data is included if it is within 6 hours of the forecast time), a model forecast is used to help with the interpolation. Therefore, technically speaking, the data provided is an analyzed data set, which is a blend of observational and model data. These analyses are then INITIALIZED.
  

Caveats:

• None

Related File Naming & Structure Information:

File Names:

• var.time.stat.nc   (In directory: /Datasets/ncep/)

Dataset Format and Size:

• PSL standard NetCDF 30 Mbyte file for each long term mean file (packed).

Missing Data:

• The data are interpolated to eliminate missing data in the dataset. However, the source data have significant gaps. This information is detailed in the file README.missing.

Citation:

• Please note: If you acquire NCEP Daily Global Analyses 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 Daily Global Analyses 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 Daily Global Analyses data set freely available online in the future. Thank you!

References:

• NMC, 1986. Packing and identification of NMC Grid Point Data.
• Randel, W.J., 1987. Global Atmospheric Circulation Statistics, 1000-1 mb. NCAR Technical Note TN-295+STR, National Center for Atmospheric Research, Boulder, CO, 245 pp.
• Trenberth, K.E., and J.G. Olson, 1988. Evaluation of NMC Global Analyses: 1979-87. NCAR Technical Note TN-299+STR, National Center for Atmospheric Research, Boulder, CO, 82 pp.
• Trenberth, K.E., and J.G. Olson, 1988. Intercomparison of NMC and ECMWF Global Analyses: 1980-1986. NCAR Technical Note TN-301+STR, National Center for Atmospheric Research, Boulder, CO, 81 pp.

Original Source:

• NCEP

Contact:

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