Land Stations used by the Climatic Research Unit within CRUTEM3
Climatic Research Unit : Data : Other

Land Stations used by the Climatic Research Unit within CRUTEM3

The file gives the locations and names of the 4138 stations used at some time (i.e. in the gridding that is used to produce CRUTEM3) during the period from 1851 to 2006. All these stations have adequate 30 year averages for 1961-90 as defined in Brohan et al. (2006). The 4138 total is lower than the 4349 value given as the starting point for Brohan et al. (2006) and used in the latest IPCC Report. A small number of stations have been removed during Brohan et al. (2006) because of the presence of duplicate data and insufficient coverage for the period 1961-90. In the file there are five pieces of information:
  1. World Meteorological Organization (WMO) Identification Number (ID)

    The WMO maintains a list of station numbers for meteorological stations to facilitate international data exchange. Unfortunately, many countries also maintain their own numbering systems and station lists for a range of operational and historical reasons. Occasionally, stations do not have a matching WMO number or have inconsistent WMO numbers.

    The numbers we use are listed in numerical order up to station number 988360. Up to this point, the numbers ending in zeroes are generally the WMO number (*10) in use for that station in the mid-1980s. Numbers not ending in a zero have generally been assigned by CRU or may have originated from other sources. Stations that are listed after number 988360 are stations for which CRU has assigned numbers, mostly beginning with 72 (so using spare country numbers not officially used by WMO) to 75 (corresponding to stations in the United States). Some WMO IDs have been updated in the 2000s.

  2. Latitude

    Latitude of the station in degrees and tenths (so 712 is 71.2 degrees N). Positive values are degrees and tenths North, with negative values for the Southern Hemisphere. These latitudes refer to the locations of the stations as defined in the mid-1980s, although some may have been updated in the 2000s. There are a number of reasons why site locations (both position and height) may have apparently changed (when, in fact, there was no site move) including, for example, more accurate mapping of locations using GPS.

  3. Longitude

    Longitude of the station in degrees and tenths (as with the latitude). Positive values are West and negative East. These longitudes refer to the locations of the stations as defined in the mid-1980s, although some may have been updated in the 2000s.

  4. Height

    Station elevation (in metres) as defined in the mid-1980s, although some may have been updated in the 2000s. Unknown elevations are coded as -999. A number of sites within the former USSR have zero elevation. This is incorrect, but this is a field that is not used by the gridding program (see later) and therefore the elevation (whether known, unknown or incorrect) does not affect the gridded data set.

  5. Name and Country

    The final field is the station name and the country. This is largely as defined in the mid-1980s, with some being updated in the 2000s. This field is also not used within the gridding. Some country names are missing, and many have not been updated for country name changes; for example the break-up of the countries of the former USSR and Yugoslavia.

Some other considerations when using these files

Gridding

The gridding process used in Brohan et al.. (2006) and earlier publications assigns each station to the 5 degree latitude/longitude box within which it is located. The gridding then simply averages all available station temperatures (as anomalies from 1961-90) within each grid box for each month from 1851. No account is taken of the station's elevation or location within the grid box (anomalies show little consistent dependence on altitude). A more up-to-date location for a station is not important for the gridding, unless a site change were to move the station to an adjacent grid box.

Updating in near-real time

The station temperature data are updated each month, together with some back data for the last couple of years. As the WMO IDs have not all been updated, we have a look-up Table which associates some current WMO station numbers with the earlier values we are using. Updates come from two principal sources [CLIMAT messages exchanged between National Meteorological Services (NMSs) and from the publication Monthly Climatic Data for the World]. Additional updates in near-real time (either monthly or annually) come directly from Australia, Canada, New Zealand, Austria, the Nordic countries and a few others.

Adding datasets (both new and improved data)

This is happening periodically. Station locations may be updated during this procedure, but not always. Resources for incorporating new data are limited, so our efforts emphasize the important aspects necessary for the gridding. This is associating recent updates with the rest of the correct station's historic record (using our WMO numbers) and merging in improved station datasets from NMSs and from scientific colleagues around the world (particularly for regions of the world where coverage is sparse). The latter involves new homogenized datasets for a number of countries and regions and also improvements and amalgamations of more than one record to single stations. Often these data arrive without WMO numbers, just NMS national numbers. We associate these with WMO numbers we use or assign new ones where this isn't possible. Keeping track of changes to country names and elevations is less important in this context.

Reference

Brohan, P., Kennedy, J., Harris, I., Tett, S.F.B. and Jones, P.D., 2006:
Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850.
J. Geophys. Res. 111, D12106, doi:10.1029/2005JD006548.