cc: Celine Bonfils , trenbert@ucar.edu date: Mon Jul 18 09:01:20 2005 from: Phil Jones subject: Re: need daily max/min or dtr climatology to: Karl Taylor Karl, The earlier email should set you up for collecting the new CRU TS 2.1 dataset. Your email about DTR is quite timely considering all the email traffic we've had on the issue over the past week. I'll try to briefly summarise this and send you some figures. Most relate to trends over the periods 1950/1-2003/4 or 1979-2003/4. Apologies for resending your figures, but together with the others we have, they are useful background. In answer to 2) there are 3 versions of DTR that we've been looking at: - one from NCDC, Russ Vose, a trend map so far for 1979-2004 - various plots from Aiguo Dai at NCAR - plots for 1950-2003 and 1979-2003 from Lisa Alexander (who is an HC employee but works at BoM in Melbourne at the moment) After your three the png file is from NCDC (Russ Vose, who's currently away). The next is from Lisa for 1951-2003 The next two are from NCDC and are trends over the USA and the final two are from Aiguo Dai and include some other fields like cloud All this may be more than you want, but these are the three versions we are potentially working with. If you look at the trends for the approximately the same periods, you will see the problems we have. Trends are often opposite for some regions (southern South America, Spain). There are some other plots as well, but these are enough for the moment. We will likely go with a trend map for 1951-2004, as these are closer. The differences for 1979-2004 reflect problems, but also are due to the period being too short. So, this answers 2) and also 4). Lisa is HC, so her version is essentially what the HC could produce. NCDC's version uses thousands of stations (~5000). Lisa's uses stations that have been collected through workshops, so QC is likely better. Aiguo's is CRU up to a point then has synop data for more recent years. Ch 3 needs to resolve these trend differences. We may not fully succeed in time for the FOD, but we need to go with one of these. As for 1), I'd suggest you use CRU TS 2.1. This will be globally complete. I would suggest you only go with the period 1951-2004 or a part thereof (i.e 1961-90 if you want). CRU is globally complete (except for Antarctica), so omit 60-90S (you seem to have done this). Also models should be land only. The best zones for the obs are 70-30N and 20-40S. Tropics less good, but I reckon the obs are not that much out Greenland isn't good in CRU. Is there a possibility of plotting a model-obs field and seeing that? Do you adjust the models for elevation? DTR tends to be higher with elevation. DTR also has a marked seasonal cycle. Can you see if the models are closer in DJF than JJA, for example? Hope these few ideas help and you can get access to the data. Kevin may have some other ideas. Cheers Phil PS I'm away after today and not back in CRU till Friday. At 00:11 17/07/2005, Karl Taylor wrote: Hi Phil, For the model evaluation chapter of the IPCC AR4 we need the climatological monthly means of daily Tmax-Tmin. Celine Bonfils, who is working with me, obtained what we needed (at .5x.5 degree resolution) from your web site and plotted the zonal mean (over land areas only). We also took the difference between the models' diurnal temperature range (DTR) and the observed. I've attached a few figures showing samples of the results for annual means of DTR. I have a few questions: 1) Do you think the observations are reliable enough to conclude that the model's largely underestimate DTR? 2) Are there alternative obs. data sets available? 3) Who should I contact at the Hadley Centre to get their HadTX and HadTN data? ([1]http://hadobs.metoffice.com/hadtx/) 4) How does your DTR climatology compare to the one at NCDC, analyzed by Tom Karl and Dave Easterling? I'm trying to get my section of chpt. 8 finished, so any quick responses would be much appreciated. thanks, Karl 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 ----------------------------------------------------------------------------