Wednesday, December 23, 2009

Station Distribution

We obtained a map of the world and downloaded the GCHN list of weather stations. We plotted the weather stations on the map. The oldest stations are red and the newest are blue. We plot the older stations last, so the numerous new stations do not cover them up. Click on the figure below for a higher-resolution version, which shows the station colors more clearly.





We see early-nineteenth century stations in Europe and North America. In the twentieth century we see the stations spreading across the world, and in particular to nations near the equator. These are the stations included in the GCHN database, which are the ones used by CRU and NCDC to obtain their global surface trend. There are, however, many more stations listed as active today by the WMO. We plot these in a separate graph. In particular, we note the large number of stations listed by the WMO in Russia, but not included in the GHCN database.
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7 comments:

  1. JeffDecember 24, 2009 at 11:07 AM

    Is the GHCN cherry-picking stations?
    The WMO stations appear to be much more numerous than the total used by the GHCN. Why would the GHCN not use every single station?

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  2. Kevan HashemiDecember 25, 2009 at 1:33 AM

    I don't know why the WMO has so many more stations. It may be that many of them don't report often enough, or perhaps they are just locations that no longer have weather stations. I have not yet found a way of getting the WMO data.

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  3. wstarckJanuary 7, 2010 at 5:04 PM

    Why not do an analysis based on stations from oceanic islands, This would be free of UHI and land use changes so should provide the best possible indication of any global temperature trend.

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  4. Kevan HashemiJanuary 7, 2010 at 5:41 PM

    That's a good idea, and there are quite a few such stations. It does seem possible that a city built up on such an island, around the weather station. But even if that were the case, the ocean island trend would be interesting. I will put this analysis on my list of things to do, and will get to it in a couple of weeks.

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  5. wowJanuary 11, 2010 at 7:57 AM

    Hi Kevan,
    You may find interesting the following article at chiefio.wordpress.com:
    GHCN – GIStemp Interactions – The Bolivia Effect
    Also of interest are the writer's comments on stations in Arctic canada.
    Hugh

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  6. Kevan HashemiJanuary 11, 2010 at 12:24 PM

    Hugh, Glad to hear from you. I may not have read and understood the chiefio post correctly, but it appears at first glance that he is confusing the average temperature of a site and the change in the average temperature from year to year. It is true that the Bolivian mountains, and the Garden Spot in Canada are colder than the stations from by their anomalies are estimated. But the mere fact that a station is colder, on average, does not mean that it is nor warming up, from year to year, at the same rate as a warmer station a thousand kilometers away.

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