To: Gavin Schmidt <email@example.com>
Subject: Re: GHCN
Date: Mon Nov 17 17:04:27 2008
First the figures are just for you - don't pass on!!! I don't normally see
these. I just asked my MOHC contact - and he's seen the furore on the blogs.
Why did the Daily Telegraph run with the story - it's all back to their readers
thinking the UK is run by another country!
These 3 paras (below) are from the GHCN web site. They appear to be the only mention
I can see of the WMO CLIMAT network on a web site. The rigorous QC that is being talked
done in retrospect. They don't do much in real time - except an outlier check.
Anyway - the CLIMAT network is part of the GTS. The members (NMSs) send
their monthly averages/total around the other NMSs on the 4th and the 18-20th
of the month afterwards. Few seem to adhere to these dates much these days, but
the aim is to send the data around twice in the following month. Data comes in
code like everything else on the GTS, so a few centres (probably a handful, NOAA/CPC,
MOHC, MeteoFrance, DWD, Roshydromet, CMA, JMA and the Australians)
that are doing analyses for weather forecasts have the software to pick out
the CLIMAT data and put it somewhere.
At the same time these same centres are taking the synop data off the system
and summing it to months - producing flags of how much was missing. At the
MOHC they compare the CLIMAT message with the monthly calculated average/total.
If they are close they accept the CLIMAT. Some countries don't use the mean of
max and min (which the synops provide) to calculate the mean, so it is important
to use the CLIMAT as this is likely to ensure continuity. If they don't agree they
check the flags and there needs to be a bit of human intervention. The figures
are examples for this October.
What often happens is that countries send out the same data for the following month.
This happens mostly in developing countries, as a few haven't yet got software to
produce the CLIMAT data in the correct format. There is WMO software to
produce these from a wide variety of possible formats the countries might be using.
Some seem to do this by overwriting the files from the previous month. They
add in the correct data, but then forget to save the revised file. Canada did
this a few years ago - but they sent the correct data around a day later and again
the second time, after they got told by someone at MOHC.
My guess here is that NOAA didn't screw up, but that Russia did. For all countries
except Russia, all data for that country comes out together. For Russia it comes
out in regions - well it is a big place! Trying to prove this would need some Russian
help - Pasha Groisman? - but there isn't much point. The fact that all the affected
data were from one Russian region suggests to me it was that region.
Probably not of much use to an FAQ!
The Global Historical Climatology Network (GHCN-Monthly) data base contains historical
temperature, precipitation, and pressure data for thousands of land stations worldwide. The
period of record varies from station to station, with several thousand extending back to
1950 and several hundred being updated monthly via CLIMAT reports. The data are available
without charge through NCDCs anonymous FTP service.
Both historical and near-real-time GHCN data undergo rigorous quality assurance reviews.
These reviews include preprocessing checks on source data, time series checks that identify
spurious changes in the mean and variance, spatial comparisons that verify the accuracy of
the climatological mean and the seasonal cycle, and neighbor checks that identify outliers
from both a serial and a spatial perspective.
GHCN-Monthly is used operationally by NCDC to monitor long-term trends in temperature and
precipitation. It has also been employed in several international climate assessments,
including the Intergovernmental Panel on Climate Change 4th Assessment Report, the Arctic
Climate Impact Assessment, and the "State of the Climate" report published annually by the
Bulletin of the American Meteorological Society.
At 12:56 17/11/2008, you wrote:
Actually, I don't think that many people have any idea how the NWS's
send out data, what data they send out, what they don't and how these
things are collated. Perhaps you'd like to send me some notes on this
that I could write up as a FAQ? Won't change anything much, but it would
be a handy reference....
On Mon, 2008-11-17 at 07:53, Phil Jones wrote:
> > Gavin,
> I may be getting touchy but the CA thread on the HadCRUt October 08
> data seems full of snidey comments. Nice to see that they have very little
> right. Where have they got the idea that the data each month come
> from GHCN? There are the daily synops and the CLIMAT messages -
> nothing to do with GHCN. All they have to do is read Brohan et al (2006)
> and they can see this - and how we merge the land and marine! They
> seem to have no idea about the Global Telecommunications System.
> Anyway - expecting the proofs of the Wengen paper any day now.
> Have already sent back loads of updated references and sorted out almost all
> of the other reference problems.
> When the paper comes out - not sure if The Holocene do online first -
> happy for you to point out the publication dates (date first
> received etc) when
> they scream that they sorted out that diagram from the first IPCC Report.
> Don't know how you find the time to do all this responding- keep it up!
> Prof. Phil Jones
> Climatic Research Unit Telephone +44 (0) 1603 592090
> School of Environmental Sciences Fax +44 (0) 1603 507784
> University of East Anglia
> Norwich Email firstname.lastname@example.org
> NR4 7TJ
Prof. Phil Jones
Climatic Research Unit Telephone +44 (0) 1603 592090
School of Environmental Sciences Fax +44 (0) 1603 507784
University of East Anglia
Norwich Email email@example.com