These files contain information in grid point order for variables which have values for each month (ie the data contained in monthly files and in scenario files. The information is the same as in the files in these other directories, only the organization is different.
We present a description of SITE_FORMAT files and a tutorial on when to use them. The tutorial includes instructions on how to translate latitude/longitude into a VEMAP grid cell number and SVF file position.
To download the tutorial directly from our ftpsite:
The naming protocol for the files is VVV_MMM where VVV describes the variable which is displayed for each month within the file and MMM gives the model from which the data was extracted. If there is no MMM part to the filename then the data is from the monthly files.
The various models are abbreviated for use in the filenames as follows:
CCC - CCC (Canadian Climate Centre)
GF1 - GFDL_R15 (Goddard Fluid Dynamic Lab R15)
GF3 - GFDL_R30 (Goddard Fluid Dynamic Lab R30)
GFQ - GFDL_QFLUX (Goddard Fluid Dynamic Lab R15 with Q-flux)
GIS - GISS (Goddard Institute for Space Studies)
MM4 - MM4 (Based on Penn State University/NCAR Mesoscale model)
OSU - OSU (Oregon State University)
UKM - UKMO (UK Meteorological Office model)
The scaling factor is the factor by which the data were multiplied before they were put into the files. To get the values back into the units described in the file header, you need to divide the values in the files by the scaling factor.
For example, latitude is given in units of degrees and hundredths of a degree and has a scaling factor of 100. This means that a value in the file of 4875 is actually 48.75 degrees, which when converted to degrees and minutes, is 48 degrees 45 minutes.
There are seven columns of standard information as well as the monthly data for the variable specified in the filename. The standard columns are the same for each file in the directory as they are physical characteristics of the grid cells and not dependent on the monthly variable in the file.
The standard columns are:
gridpoint, latitude, longitude, elevation, vveg2, Küchler_veg, stateand each of these is explained below. Following this are twelve columns containing the data by month so each line of the file begins with the appropriate gridpoint and ends with the data value for December.
Information on the format of the site files and how to find data for specific locations is available here.
The grid used for the VEMAP coverage is a 0.5 degree latitude by 0.5 degree longitude grid covering the conterminous U.S. Grid edges are aligned with 1.0 degree and 0.5 degree lat/lon lines (centers at 0.25 degrees and 0.75 degrees).
The grid's minimum bounding rectangle (MBR) is defined by the following corners:Lower Left Corner => -124.5 degrees lon, 25.0 degrees lat Upper Right Corner => -67.0 degrees lon, 49.0 degrees lat where negative longitudes are degrees West.
Gridpoint number starts at 1 in the far north west corner of the bounding rectangle and finishes at 5520 in the south east. There are 115 gridpoints across the domain and 48 down. Gridpoint position is shown in the diagram below.
--------------------------------------- |1 2 3 4 5 6... ...114| |115 116 117... ...229| |230... | | | | | | ...5520| ---------------------------------------
Not included in the site files are gridpoints where more than half the cell is not land area within the conterminous US. Most of these points are around the edges of the map but some interior cells are excluded such as Great Salt Lake or river inlets. This means that each file is in fact only 3261 lines long and that the gridpoint number is not sequential.
For a listing of the codes used for the vegetation classification click here
For a listing of the codes used for the Küchler vegetation classification click here
For a listing of the codes used for each of the states click here
For a listing of the files click here
Back to the first page