cc: Sakari Uppala date: Mon Mar 8 10:37:31 2004 from: Phil Jones subject: Re: November 1981 in CRUTEM2v, ERA-40 and NCEP to: Adrian.Simmons@ecmwf.int Adrian, Found the problem and it is in the CRU data. It is also in World Weather Records and likely in the GHCN dataset at NCDC as well. We are going to trawl through some files for Turkey that we have and see if we can find the correct data in them. I recall putting this data in so maybe that was wrong as well. The data we have for Nov 81 looks like another month - maybe Sept or Oct. If we have to contact Turkey it may take a little time to get the right data. Best to omit that month for the time being. Also, Turkey has a lot of missing data in 1981 for some reason. Will try and infill that at the same time. Cheers Phil Adrian, I'll look into this. I vaguely recall some odd months during the 1980s which we discovered in some comparisons then. I'll have to go back to some older files and check with some more recent Turkish data we've received. During that time we were putting the CLIMAT messages in by manual means. We've since received the World Weather Records for Europe (RA6, so including Turkey), so any values should have been replaced by these numbers directly from the country. It may take me a few hours to get to the bottom of this. Cheers Phil At 12:36 06/03/2004 +0000, Adrian Simmons wrote: Phil I found a few hours to work on the reanalysis/CRU comparisons this morning, and decided to plot the differences between CRU and ERA-40, and between CRU and NCEP, month-by-month. Basically, it showed ERA-40 in a good light, assuming CRU to be truth. However, November 1981 over "Europe" was anomalous, as can be seen in the attached time series. The NCEP curve is hidden beneath the ERA-40 curve for this month: both are unusually different from CRUTEM2v. For ERA-40, it's the largest discrepancy in the series. I thus plotted out values for each of the grid boxes that go into the average for this month. The problem is confined to the south-east of the domain - strictly Asian boxes rather than European ones (though we have all of Turkey as a Member State!). Here are the anomalies relative to 1961-1990 for the three boxes with the largest discrepancies: Lat: 45N-40N Lon: 30E-35E CRUTEM2v: 7.75 ERA-40: -1.39 NCEP: -1.14 Lat: 40N-35N Lon: 30E-35E CRUTEM2v: 6.85 ERA-40: -1.69 NCEP: -2.66 Lat: 40N-35N Lon: 35E-40E CRUTEM2v: 4.28 ERA-40: -1.59 NCEP: -2.76 As you can see, it is the CRUTEM2v values that are the most anomalous. I hope I haven't made a mistake in my processing of the CRUTEM2v data. Assuming not, I'd appreciate your comments on this. Are you aware of any problem with the data in this region? Best regards Adrian -- -------------------------------------------------- Adrian Simmons Head of Data Division European Centre for Medium-Range Weather Forecasts Shinfield Park, Reading, RG2 9AX, UK Phone: +44 118 949 9700 Fax: +44 118 986 9450 -------------------------------------------------- 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 p.jones@uea.ac.uk NR4 7TJ UK ----------------------------------------------------------------------------