VEMAP Phase 2 Transient Climate Dataset

Annual and Monthly Historical Climate (1895-1993)

1 March 2001


(1) VEMAP 2 Transient Climate Dataset - Historical Climate

(a) Annual Files

NetCDF annual files (99 years of annual records)
Period of Record: 1895 - 1993
3261 non-background values for the contiguous US.

The annual data are available on ORNL DAAC's anonymous FTP site:

> ftp
> cd pub/data/vemap-2/TCLIMATE/annual/data
> binary (Note: transfer files in binary mode)

(b) Monthly Files

NetCDF monthly files (99 years of monthly records = 1188 records)
Period of Record: Jan 1895 - Dec 1993
3261 non-background values over the contiguous US.

The monthly data are available on ORNL DAAC's anonymous FTP site:

> ftp
> CD pub/data/VEMAP2/TCLIMATE/monthly/data
> binary (Note: transfer files in binary mode)

(c) Daily Files

Daily files are available in partial-grid format only. These netCDF files contain records in xyt format for only those cells containing data. Record number will not correspond with grid cell location.

They are available on CD through ORNL DAAC
and on 8mm Exabyte tape through the NCAR VEMAP Data Group.

(d) File Name Convention


Formula: where:
vvvv = variable 
  tmax = maximum temperature
tmin = minimum temperature
pptx = precipitation
irrx = mean daily irradiance
srad = total incident solar radiation
rhum = relative humidity
vpxx = vapor pressure
SSSS = dataset 
  TCLM = historical climate (1895-1993)
CCC1 = CCCma CGCM1 scenario (1994-2100)
HAD2 = Hadley HadCM2 scenario (1994-2099)
TCC1 = hist clim + CCCma scen (1895-2100)
TCH2 = hist clim + Hadley scen (1895-2099)
aa = aerosol experiment
  Su = sulfate aerosols
xx = not applicable
T = time step
  A = annual
M = monthly
D = daily
r = release number
g = type of grid
  p = partial grid (only non-background grid cells in file)
i = full (inflated) grid (all grid cells in file)
nc = netCDF suffix
gz = (applicable only if compressed) compressed using UNIX gzip utility

Note (UNIX): To uncompress the files, type:
gunzip <filename>.gz

(e) Geography and VVEG Version

Geographic information is included in each netCDF file describing the VEMAP grid:
- latitude
- longitude
- time
- elevation of cells with land cover [m]
- varea: the area of each grid cell covered by land [km2]
- vveg(v2): VEMAP vegetation classification
- grid mask counter (1->3261 for non-background grid cells; 0 for background grid cells)
This version of VVEG reflects minor changes to the classification and distribution of potential natural vegetation suggested during VEMAP Phase 1. For details on VVEG version 2, see Section 10 and Appendix 3 in "A User's Guide to the VEMAP Phase 1 Database" (available on the VEMAP web site [] and hard copy).

(f) Units

Units are described in the netCDF file header.

(g) NetCDF file format

The files are written in netCDF format (binary rather that ASCII). (See the Appendix for more information on general NetCDF format and source code.) . The netCDF files contain monthly or annual values for each grid cell over the contiguous United States. Backgroud cells containing no data are represented as missing with -9999.0. This format is referred to as "full grid", as compared to the "partial grid" fomat of earlier VEMAP releases in which the file only included the non-background grid cells.

The netCDF files are in sequential or "movie" format with the complete time slice of the U.S. for the first year, followed by the complete time slice of the US for the second year, etc. (i.e., (time,lat,lon)). The order of the grid cells is west to east, north to south. Each grid cell is 0.5 degree latitude by 0.5 degree longitude. The data values are given for the center of the grid cell. There are 3261 non-background cells out of 5520.

(UNIX) To output a netCDF file to the screen in ASCII format, type:

ncdump <filename> | more (or 'less')
Or for just the header (meta data), type:
ncdump -h <filename> | more (or 'less')

(h) NetCDF Data Display and Analysis

Many options exist to edit, display, and analyze data in netCDF format. NetCDF files can be read by C, FORTRAN, Java, and Perl programs using netCDF libraries. NCO (a suite of netCDF operators) provides command line options for editing, averaging, subsetting, and merging netCDF files. Other software programs are available to display and edit netCDF files on a variety of platforms. Descriptions of these and other netCDF tools can be found on the following web pages:

See the Appendix for more information on NetCDF.

(2) Historical C02

Twice-yearly historical time series of global atmospheric CO2 concentration is provided in the ASCII file:
This dataset is based on the spline fit of Mauna Loa and ice core data from Enting et al. (1994), updated by T. Wigley (2000). The data start in 1765.

(3) Wind Speed

For a wind speed dataset, we recommend that modeling groups use the monthly wind data from VEMAP Phase1, stored in SVF ASCII format and available from the NCAR Data Group:

(4) Data Use Policy + Citations

Use of the VEMAP 2 dataset is subject to the VEMAP data policy ( Please register with the VEMAP Data Group in order to be informed of updates or revisions.

Users are requested to confer with the NCAR VEMAP Data Group to ensure that the intended application of the dataset is consistent with the generation and limitations of the data.

Please cite data as:

Kittel, T.G.F., J.A. Royle, C. Daly, N.A. Rosenbloom, W.P. Gibson, H.H. Fisher, D.S. Schimel, L.M. Berliner, and VEMAP 2 Participants (1997). A gridded historical (1895-1993) bioclimate dataset for the conterminous United States. Pages 219-222, in: Proceedings of the 10th Conference on Applied Climatology, 20-24 October 1997, Reno NV. American Meteorological Society, Boston.

Kittel, T.G.F., NA Rosenbloom, C. Kaufman, JA Royle, C. Daly, H.H. Fisher, WP Gibson, S. Aulenbach, R. McKeown, D.S. Schimel, and VEMAP2 Participants (2000). VEMAP Phase 2 Historical and Future Scenario Climate Database. Available online at [] from the ORNL Distributed Active Archive Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee, U.S.A.

(5) Contacts

If you have technical problems or questions about these files, please contact ORNL DAAC or the VEMAP Data Group.


NetCDF refers to the Network Common Data Form developed by Unidata (within the University Corporation for Atmospheric Research). NetCDF software is an I/O library that is callable from C, FORTRAN, C++, Perl or other language for which a netCDF library is available. The library stores and retrieves scientific data structures using self-describing, machine-independent files.

The netCDF source is freely available and can be obtained as a compressed tar file or a zip file from Unidata. Extensive documentation, source files, and software for manipulating or displaying netCDF data can be found online at:
Please refer questions about building or installing netCDF software to UNIDATA
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