date: Fri Aug 5 16:12:50 2005 from: Phil Jones subject: Re: DTR trends to: "Russell Vose" , Adrian.Simmons@ecmwf.int Adrian, Russ and me have been having some email exchanges about which of your two datasets we need. We have maps of DTR from Russ (the one he emailed you an hour or so ago) and from Aiguo Dai and Lisa Alexander. I've been concentrating on Australia (as we have maps of trends from BoM for 1950-03 and 1979-03 (attached). Maybe Australia isn't the best place to look but we're confident BoM is likely to be right. Of the time series you sent, Australia shows the largest difference between the 0-6h forecast and the 6 hrly analyses, particularly from about 1990. This divergence since 1990 also occurs in other regions although not over North America nor much over Europe, which suggests it is something to do with the data. This divergence isn't an issue in the mean temp from the 2004 paper, so any thoughts. Russ thinks the 6 hrly analyses look better compared to his plot, but I reckon that the 0-6hr forecasts are better in some regions. So, is it possible to send both datasets. Russ can cope with the format. Cheers Phil At 14:31 05/08/2005, Russell Vose wrote: Adrian: Many thanks for these figures. At first glance it appears that my analysis for 1979-2004 and yours for 1979-2001 (6-hrly analysis) exhibit some general agreement. It's not a perfect match, but both suggest that many areas (western U.S., Europe, western Asia, Australia) experienced an increase in DTR since 1979. Do you have a global (land surface) trend for 1979-2001 for the 6-hrly analysis? Adrian Simmons wrote: Phil Attached are a set of results based on DTR computed both from the max/min temperatures in the four daily 0-6h forecasts and from the max/min of the analysed temperatures for 00, 06, 12 and 18UTC. No mask based on CRUTEM2V has been applied, but I've masked out sea points, based on selecting only 5deg boxes that are more than 50% land. The first two attachments show maps of the least-square linear trends in DTR computed for 1958-2001 and 1979-2001. The third attachment shows time series of some area averages. These are plotted as deviations from the 44-year mean, and smoothed by a 12-month running average. Clearly there are some things here that must be treated with much suspicion - the drop from the 60s to the mid-70s in the tropics (and southern hemisphere?) for example is suggestive of a shift in the assimilation associated with change in data coverage. perhaps, though, there is something useful in the information for Europe (at least from 1967 onwards after the SYNOP coverage improves) and North America. Best regards Adrian Phil Jones wrote: Adrian, Is it a trivial exercise for you to work a trend from land regions of DTR (annual) for 1979-2001? I'm just after a number. Does ERA-40 have DTR still going down? CRU mask not essential. Omit Antarctica. If it isn't trivial then don't bother. Cheers Phil At 17:04 03/08/2005, Adrian Simmons wrote: Phil, Russell As promised earlier, attached is the first of the datasets. It is the set of monhtly-averages of the daily maximum two-metre temperature, computed from the four 0-6h forecasts per day carried out from the ERA-40 analyses. Once you have run gunzip on the dataset, you should be left with a simple character file, suitable for a formatted read into a FORTRAN program. Looking at the file with any editor, you should see a sequence comprising a month identifier (format is I4,I2) showing YYYYMM and then the field itself. Each row (format 72f7.2) contains the temperature in Kelvin for grid boxes running east from the dateline, ie for longitudes 180W-175W, 175W-170W, 170W-165W,..., 175E-180E, as in the CRUTEM2V dataset downloadable from the CRU website. There are 36 rows running from north to south, ie for latitudes 90N-85N, 85N-80N,80N-75N,...,85S-90S. The months run from 1958 1 to 200112. If you can read the data without problem, I'll send the corresponding monthly-average minimum temperatures computed the same way, and the alternative monthly averages of the max/min temperatures computed each day from the 00, 06, 12 and 18UTC analyses. I'll send one field per email to avoid hitting possible mailbox limits. 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 ---------------------------------------------------------------------------- -- Russell S. Vose, Chief Climate Analysis Branch National Climatic Data Center 151 Patton Avenue Asheville, North Carolina 28801 Phone: (828) 271-4311 Fax: (828) 271-4328 E-mail: Russell.Vose@noaa.gov 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 ----------------------------------------------------------------------------