WORLDCLIM 

On this page there is information about WorldClim data format, file names and file format.

Data Format

These layers (grid data) cover the global land areas except Antarctica. They are in geodetic coordinate system (not projected, i.e., 'GEOGRAPHIC' or 'LATLONG' system). The datum is WGS84. They are available at 4 different spatial resolutions; from 30 seconds (0.93 x 0.93 = 0.86 km² at the equator) to 2.5, 5 and 10 minutes (18.6 x 18.6 = 344 km² at the equator). The original data were at a 30 second resolution, the other data have been derived through aggregation, by calculating the mean of groups of cells. Cells with 'no data' were ignored. In other words, if some of the original cells were on land, and some cells were on sea, the aggregate cells have data. Only if all original cells have 'no data' then the aggregate cell has 'no data'. Aggregation was done for monthly precipitation, minimum, mean and maximum temperature. The Bioclimatic variables were calculated from these aggregated data.

File Names

The data are stored in ZIP (compressed) files. There is a ZIP file for each combination of resolution/format and climate element (mean, min, and max monthly average temperature and monthly total precipitation), the bioclimatic variables, and altitude. 

The ZIP files have names like X_R_F.ZIP, where X indicates the variable (TMEAN, TMIN, TMAX, PREC, BIO, or ALT); R indicates the resolution (10m, 5m, 2_5m, 30s); F indicates to format: 'BIL' for generic grids, and 'ESRI' for ESRI grids. For example, the file TMIN_5m_BIL.ZIP has the minimum temperature data, at 5 minute resolution, in generic grid format.

The ZIP files with climate element data contain 12 data layers (one for each month); the bioclimatic ZIP file contains 19 data layers; and the altitude ZIP file contains one layer. There are small differences between filenames based on their resolution/format, but basically they are like specified below:

tmean<m>_<r>.ext
tmin<m>_<r>.ext
tmax<m>_<r>.ext
prec<m>_<r>.ext
bio<x>_<r>.ext
alt_<r>.ext

tiled data 

The tiled data comes in 30 x 30 degree tiles, each consisting of 3600 rows and 3600 columns. 

Tiled data (only available for 30 second resolution, and in generic grid format) has a slightly different syntax:

tmean<m>_<z>.ext
tmin<m>_<z>.ext
tmax<m>_<z>.ext
prec<m>_<z>.ext
bio<x>_<z>.ext
alt_<z>.ext

In which z = zone, from 00 to 411, see map on download page (only for 30-seconds resolution)

File Format

1) ESRI grid (raster) format.

For use with ESRI products (ArcSomething). The ZIP files should be uncompressed into a new folder. Each grid is stored in a subfolder. There is also an INFO folder that should remain with these grids (for more information see your ESRI manuals). 

2) Generic grid (raster) format.

Each layer consists of two files. One file with the actual data (.BIL); and one accompanying text (header) file (.HDR). Sometimes there are two more header files (.GRD and .RDC) for use in DIVA-GIS or IDRISI (see below).  The data files (.BIL) are sequential binary files in which values are stored line by line from the upper-left to the lower-right corner. Each cell (pixel) is an integer value (2 bytes; -32768..32767).

Importing the generic grid data into your GIS application

The WorldClim data can be easily imported into most GIS applications. Here is some help:

ArcInfo:  Use the "imagegrid" in command-line ArcInfo

              For the tiled data (generic format) only:
             Download the data for the tiles you want.
             To stitch the files together:
                 Copy this file: WorldClim.aml to that directory (right-click and "save target as")
                 Open a command-line "Arc" window
                 Go to the folder where your unzipped data files are. Type, for example, Arc: w  c:\worldclim
                 Type grid (and press enter)
                 Type &run worldclim.aml (and press enter)

             For a workaround: download the data for the tiles you want.
              Use DIVA-GIS (free download; see below)
             Data\Import to gridfile\Multiple Files (BIL/BIP/BSQ) and then
             Data\Export to gridfile\Multiple Files (ESRI Ascii)
             in ArcView open a View, and use File/Import data source/Ascii raster

            If you simply open the data as images or raster data sets, there is a problem. ESRI software assumes that BIL files
           do not have negative values. These values (x) are replaced by (65535 - x); E.g., -10 becomes 65525. The nodata value of -9999 is not recognized...
           a BIG mess results.

Idrisi:     Unzip the files 
            import the data using the *.bil and *.hdr files.
            Some of the .ZIP files also contain .RDC files. If you rename the .BIL files to .RST. they can be opened in IDRISI without the import procedure
            Renaming is easy in command line (DOS) window. E.g., "D:\worldclim\ren  *.bil  *.rdc"

DIVA-GIS: Unzip the files 
              Use: Data\Import to gridfile\Multiple Files (BIL/BIP/BSQ)
             Some of the .ZIP files also contain .GRD files. If you rename the .BIL files to .GRI. they can be opened in DIVA-GIS without the import procedure
             Renaming is easy in command line (DOS) window. E.g., "D:\worldclim\ren  *.bil  *.rdc"

Manifold GIS: Import the generic grid files with Import\Surface...\BIL Files (*.bil;*.hdr).
                Set the Current Projection by right clicking the surface in the 
              Project Panel\Projection\Current Projection\Latitude/Longitude.