Saturday, April 12, 2014

More GHCN QC errors

My previous post was on some specific problems in the March GHCN data (monthly TAVG QCU). At this stage that data is newly posted, and while the errors should not have passed QC, they will probably be corrected. I imagine that Greenland, for example, will be sorted once the CLIMAT form comes in.

But I'm finding data points going back, which should have been eliminated by QC. It seems there may be a general failure.

For example, in February, Kwajalein, in the Marshall Islands, had an average of -2.3°C. Historically, it's a pretty steady 28°C at that time. That one was in the CLIMAT form, but should have been picked up. Not so far away, in Truk December 2011, it was 0°C. Again in the CLIMAT form.

Port Hardy, on Vancouver Island, BC, is a very strange case. It seems to have an equable climate. But in February, GHCN gives it -27.5°C. -25.3 in January, -26.4 in December 2013. And other icy spells, like -24.1 in December 2011. This time it isn't the CLIMAT reports, which seem OK. Instead, Port Hardy has been getting the data for Clyde River, in Nunavat, Lat 70°N. This seems to have happened at least 13 times since 2009.

But even more spectacularly, La Paz, in Bolivia, reached 86°C in June 2010, and 83°C in June 2011. The latter seems to have been a reinterpretation of the 53°C in the CLIMAT form. La Paz is normally around 7°C in June. That's not the record, though - Oruro in Bolivia in September 2011 reached 90°C. This and the 2010 La Paz rading were not in the CLIMAT forms. They may have been removed. The issue seems to be decimal points.

The problems are not common, and often relate to errors in the data submitted. But I can't see why they aren't being picked up.


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