Tuesday, August 3, 2010

GE visualisation of changes to GHCN stations 1990-2007

At WUWT there is a post about Ross McKitrick's discussion of supposed defects in GHCN, focussing heavily on changes in the stations in the dataset between about 1990 and 2005+. So I've made some KMZ files so interested people can see in detail what those changes were.

This post follows three recent previous posts here about KMZ files for GHCN type datasets:
Briefly, a KMZ file is a compressed file of data which you can read into Google Earth. You can just click on the filename in a file browser, or use the GE open facility (or Ctrl-O). When you open it, you will see a subset of the GHCN stations marked with placers (pushpins). These show (when you get close) the station names, and indicate other properties thus:
  • Color - rural stations are green, urban yellow. Orange is a small town.
  • Size. Big pins have >50 yrs data. 70% pins have >20 yrs, and 40% have less.
  • Balloon - clicking on a station gives a balloon with several data items, including years of reporting.

The files


You can find the files on the data repository. They are in a zip file KMLGHCNends.zip which you can download (scroll down). The individual files are:
  • GHCN1900end.kmz, which has stations that dropped out of the database between 1991 and 2000
  • GHCN2000end.kmz, which has stations that dropped out of the database between 2001 and 2007
  • GHCN1900st.kmz, which has stations that were added between 1991 and 2000
  • GHCN2000st.kmz, which has stations that were added between 2001 and 2007
There weren't many stations added, so you might want to skip the last two files.

Below the jump, I'll add some still pictures from GE.





Here are the US stations that were dropped from GHCN between 1991 and 2000:



Australia was very densely represented pre-1990, so many did not continue:


African stations in W Africa and S Africa were not continued:



Arctic losses were not large:


Europe lost a few stations, including a bunch of short-record ones in Yugoslavia



Between 2001 and 2007 the big change was US numbers - tied in with the interaction with USHCN, which GISS incorporates separately.



2 comments:

  1. Are you sure about the Canadian stations.
    I have the impression that more were dropped especially in the Arctic.

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  2. Gerald,
    I believe that a number did not report for a period in 2008-9. I looked only at stations dropped to 2007. Part of the reason was that stations sometimes do cease reporting for a while, but revive. I think that was true of some of the Canadian ones. In fact, I looked on Ogimet, and it seems that the Canadian stations were still sending in CLIMAT reports, including the actual monthly data, but with some other info omitted. I don't know the background there.

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