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NCEP/NCAR Reanalysis Monthly Means and Other Derived Variables

One-Line Description:

  • NCEP/NCAR Reanalysis Monthly Means and Other Derived Variables..

Temporal Coverage:

  • Daily and Monthly Values for 1948/01 - present.
  • Long term monthly means, derived from data for years 1968 - 1996.

Spatial Coverage:

    Spatial coverage:
    • T62 Gaussian grid with 192x94 points
    • 88.542N-88.542S, 0E-358.125E

Levels:

  • 2 Sigma levels: 0.995,0.2101 for monthly means
  • 5 sigma levels 0.995 , 0.8458 , 0.2582 , 0.2101 , 0.1682 for daily chi,psi

Update Schedule:

  • Monthly

Download/Plot Data:

Variable Statistic Level Download File Create Plot/Subset
Air temperature air degC mon mean,ltm,daily ltm,
      diurnal cycle (4 different months)
      1st 2 eofs NH, calculated
      separately for each level
Geopotential height hgt m mon mean,ltm,daily ltm
      diurnal cycle (4 different months)
      1st 2 eofs NH, calculated
      separately for each level
Relative humidity rhum % mon mean,ltm
Specific humidity shum g/kg mon mean,ltm,daily ltm
Omega (vertical velocity) omega Pascal/s mon mean,ltm
U-wind uwnd m/s mon mean,ltm,daily ltm,
      1st 2 eofs NH, calculated
      separately for each level
V-wind vwnd m/s mon mean,ltm
Land-sea mask (time invariant) * lsmask (0 or 1) none
Derived variables include: File Units Statistics Available

Usage Restrictions:

  • None

Detailed Description:

  • Cort Willmott & Kenji Matsuura of the University of Delaware have put data together from a large number of stations, both from the GHCN (Global Historical Climate Network) and, more extensively, from the archive of Legates & Willmott. The result is a monthly climatology of precipitation and air temperature, both at the surface, and a time series, spanning 1950 to 1999, of monthly mean surface air temperatures, and monthly total precipitation. It is land-only in coverage, and complements the ICOADS (International Comprehensive Ocean-Atmosphere Data Set) data set well. The version we have stored online is 1.02 and some values will have changed from our 1950-1996 files. For a complete description of the data as given by the providers and references to relevant papers please see their web pages at the University of Delaware.

Caveats:

  • None

Related File Naming & Structure Information:

File Names:

  • var.time.stat.nc   (In directory: /Datasets/udel.airt.precip/)

Dataset Format and Size:

  • CDC standard NetCDF 311 Mbyte file for each monthly file (packed).
  • CDC standard NetCDF 30 Mbyte file for each long term mean file (packed).

Missing Data:

  • Missing data is flagged with a value of 32767s.

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 UDel_AirT_Precip 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 UDel_AirT_Precip data provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, 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 PSD to justify keeping the UDel_AirT_Precip data set freely available online in the future. Thank you!

References:

  • Legates, D. R. and C. J. Willmott (1990a) Mean Seasonal and Spatial Variability Global Surface Air Temperature. Theoretical and Applied Climatology , 41, 11-21.
  • Shepard, D. (1968) A two-dimensional Interpolation function for irregularly-spaced Data. Proceedings, 1968 ACM National Conference, 517-523.
  • Willmott, C. J., C. M. Rowe and W. D. Philpot (1985) Small-Scale Climate Maps: A Sensitivity Analysis of Some Common Assumptions Associated with Grid-point Interpolation and Contouring. American Cartographer, 12, 5-16.
  • Willmott, C. J. and K. Matsuura (1995) Smart Interpolation of Annually Averaged Air Temperature in the United States. Journal of Applied Meteorology, 34, 2577-2586.

Original Source:

  • Center for Climatic Research Department of Geography University of Delaware Newark, DE 19716 The University of Delaware Web site offers extensive documentation of this data set. Please address questions on the analysis method to Kenji Matsuura (kenjisan@udel.edu) University of Delaware.

Contact:

  • Physical Sciences Division: Data Management
    NOAA/ESRL/PSD
    325 Broadway
    Boulder, CO 80305-3328
    esrl.psd.data@noaa.gov

Sigma Level Variables

Archive parameters: File names are generally composed of variable abbreviations, averaging period and statistic. Averaging periods include "mon" and day. Daily files just have the year in their names (as in psi.1995.nc). Statistics include "mean" and "ltm" (long-term mean). (variable).(averaging period).(statistic).nc

Variables: File Units Statistics Available
Divergence div 1./s mon mean,ltm
Relative Vorticity vort 1./s mon mean,ltm
Derived File Units Statistics Available
Velocity Potential chi m*m/s mon mean,ltm,day
Streamfunction psi m*m/s mon mean,ltm,day

Note:

These variables are averages of instantaneous values at the 4 reference times; 0,6,12 and 18z over the averaging period (month).

Temporal coverage:

Levels: Missing data: Search keywords:
Divergence, relative vorticity, streamfunction, velocity potential

Data set format and size:

Availability and usage restrictions:

How statistics were calculated

Means
These are calculated by averaging the 4 times daily data into monthly means. In some cases, the units were changed from the original NCEP data. Means are generally from 1948-present though some variables are available for a subset of that period.
Long-Term Means
These are calculated by averaging the monthly means from 1968-1996 (for most variables) That time period was used to avoid some of the problems before 1968. Long-Term means will not be recalculated at the end of each new year (so that they are stable). Some variables use a different climatology time period.
Interannual Standard Deviation
The long-term mean is subtracted from the mean for each year and that squared number is averaged over all years and then the square root is taken. It represents the average deviation from the mean from the long-term mean.
Intraannual Standard Deviation
A sum of the squares of the 4 times daily values minus the monthly value for that month/year is calculated for all days in a particular month for all years. The average of this number is the intraannual standard deviation.
Daily Long-Term mean
The data for a particular day of the year is averaged over a set of years (1968-1996). Feb 29 data is ignored.
Diurnal Cycle
The monthly mean of each of the 4 daily time periods (0,6,12,18z) is calculated.

Other General Information

CDC internal (netopen) identifier:
Original Source:

NOAA National Center for Environmental Prediction (NCEP)

Archive location(s): Climate Diagnostics branch of ESRL/PSD
325 Broadway
R/PSD1
Boulder, CO 80305-3328

Contact person(s):
Climate Diagnostics Data Management
Climate Diagnostics branch of ESRL/PSD
325 Broadway
R/PSD1
Boulder, CO 80305-3328
cdcdata@noaa.gov