On Feb 20, 2008, I wrote a post reviewing the provenance of various versions of an individual USHCN station (Lampasas), observing that a much more recent version was available at NOAA than at CDIAC) (the source used by NASA. I made the following recommendation:
Regardless of whether these station histories “matter”, surely there’s no harm in NASA (and GHCN) adopting rational approaches to their handling of the USHCN network. To that end, I would make several recommendations to NASA:
1. Use the NOAA USHCN version rather than the stale CDIAC and/or GHCN versions.
2. Lose the splice and the patch.
3. Use USHCN interpolations rather than Hansenizing interpolations.
4. Use TOBS or perhaps MMTS, and if MMTS is used, ensure that NOAA places this online.
A reader observed that, on March 1, 2008, NASA announced the implementation of the first recommendation.
March 1, 2008: Starting with our next update, USHCN data will be taken from NOAA’s ftp site rather than from CDIAC’s web site. The file will be uploaded each time a new full year is made available. These updates will also automatically include changes to data from previous years that were made by NOAA since our last upload. The publicly available source codes were modified to automatically deal with additional years.
No mention was made of the CA recommendation (although they seemed to be aware of the CA discussions, as they altered the legend on one of their station inventory webpages inserting a caption to a series then under discussion here.)
They didn’t mention anything about the patch – recommendation 2. It will be worth checking to see how they implemented the new version. The most logical approach (recommended by CA) would have been to use the NOAA USHCN Filnet version, which did away with any need for a patch (this patch arose out of the Y2K correction – they calculated patches for all 1221 USHCN stations so that there was no Y2K step between the GHCN Raw version and CDIAC SHAP/Filnet versions). If they use the NOAA USHCN Filnet version consistently, then there is no need for the calculation of a patch; plus, their series will be traceable back to its sources.
It is, of course, possible that they’ve continued to pull post-2005 data from USHCN Raw (NOAA up to date version) and pre-2005 version from USHCN Filnet and continued to estimate a patch between the two. It would be pretty silly if they did and I hope that they don’t. (The new method is not yet implemented in the online database).
They’ve slightly edited their methodology page to reflect the changed procedure. As a source, instead of CDIAC, they now show:
For US: USHCN – ftp://ftp.ncdc.noaa.gov/pub/data/ushcn
This doesn’t make clear which USHCN version they use – something that should be shown in this page. They continue to describe a splicing step. This may simply be an oversight or they may plan to continue splicing.
Replacing USHCN-unmodified by USHCN-corrected data:
The reports were converted from F to C and reformatted; data marked as being
filled in using interpolation methods were removed. USHCN-IDs were replaced
by the corresponding GHCN-ID. The latest common 10 years for each station
were used to compare corrected and uncorrected data. The offset obtained in
way was subtracted from the corrected USHCN reports to match any new incoming
GHCN reports for that station (GHCN reports are updated monthly; in the past,
USHCN data used to lag by 1-5 years).
As to the headline – NASA did not credit CA in announcing the changed procedure. Perhaps the timing was simply coincidence. In any event, the net result is a slight improvement in NASA’s methodology and so we can all take some comfort in that.