date: Tue Mar 24 10:59:17 2009 from: Tim Osborn subject: Re: Northern Latitude differences to: Deborah Hemming Hi Debbie, I took at look at the 1951-2000 Jan pattern -- as you say, it is still amplified at the poles compared to our CMIP3 HadCM3 pattern. Chris suggested this could be due to a genuine difference in model versions. Have you got the other 11 months for the longer 1951-2000 period yet? I'll take a look at them if you have. Cheers Tim At 19:40 06/03/2009, you wrote: Tim, Sorry I havnt been able to finish the patterns, attached is the January pattern for the standard run 1951-2100 30 year running mean, it is improved but still too amplified in the poles. Unfortunately, I am away now for 2 weeks so will have to sort this out when i'm back. Sorry again for the delay. Cheers, Debbie. On Wed, 2009-03-04 at 14:27 +0000, Tim Osborn wrote: > Thanks for that Debbie. Please note that I did *not* used 1900-2100 > for the regressions. We used 1951-2099 or 1951-2100 depending on > which year the runs finished in. Feel free to also do 1900-2099/2100 > to investigate sensitivity to this further, if you want, but with > 1951-2099 you've already replicated our analysis period so you could > just send those new patterns if you like. > > re. sensitivity. yes, the 20th century has lower slope in the local > changes, but also lower slope in the global-mean temperature that is > being regressed against. So, you wouldn't definitely get a > sensitivity to period of analysis. However in sea-ice areas this > might be more non-linear and hence the biggest local changes might > only occur after some degree of global warming, which could lead to > the effect that you describe. This also invalidates the > pattern-scaling concept, but for surface air temperature I only > pattern-scale over land, so the Arctic sea-ice area isn't much of a > concern. Of more concern are the N. American differences in Jan-May, > which are over land. It would be nice to see if your new 1951-2099 > patterns match mine better in this region. > > Cheers > > Tim > > At 14:19 04/03/2009, Deborah Hemming wrote: > >It seems that the difference may be because of the different time period > >over which the regression was performed. I've just compared my previous > >output (2000-2099 period 30 year running mean) with the same but for the > >period 1951-2099, which is closer to the 1900-2100 period Tim uses. > >This second pattern is ~2C lower (more comparable with Tim's) in the > >polar regions than the first. > > > >This completely makes sense to me because the lower slope of the > >relationship during the 20th century is forcing the regression slope to > >be lower...esp in the high change regions. However, I really hadn't > >expected it to be so sensitive, which is somewhat disturbing! I want to > >check a couple more ideas and extend the time to cover the whole > >1900-2100 period, which i'll probably have to do overnight, but should > >be able to send some more reasonable QUMP patterns, at least for average > >temperature, to Tim tomorrow. > > > >Sorry this is taking so long to sort out, but it's very useful for me at > >least to appreciate the scale of differences that subtle variations in > >the methods used for pattern scaling can make. I think this also > >justifies us being very careful to use the same method for all data in > >QUEST-GSI. > > > >Cheers, > >Debbie. > > > >On Wed, 2009-03-04 at 13:38 +0000, Tim Osborn wrote: > > > something like Chris' suggestion below seems more likely than a bug > > > in your code, Debbie. A bug would more likely either make the > > > results unrecognisable or, if more minor, affect results more widely > > > rather than having a high-latitude focus. > > > > > > Tim > > > > > > At 19:23 03/03/2009, Chris Huntingford wrote: > > > >Dear Debbie (cc Ben Booth) > > > > > > > >I can cover on Thursday. > > > > > > > >I was thinking about the GCM differences. There were a couple of > > > >small bugs that we found in HadCM3 land surface description that we > > > >didn't think made much difference when tested back in a full GCM > > > >simulation. Martin Best knows what the problems are, but I do have > > > >the vague memory of somebody saying they are most likely to make the > > > >largest differences in Northern Latitudes, mainly due to snow > > > >interactions. The "correct" simulation, hopefully bug-free, was made > > > >by Spencer Liddicoat, and the patterns are those that I sent you. > > > >Job number "afsyb". > > > > > > > >When we fitted the patterns to the QUMP runs, I cannot remember > > > >whether Ben Booth made patterns for the standard run too - I'm happy > > > >to make an intercomparison. Ben, do you have IMOGEN patterns for the > > > >control i.e. for each month - I'm struggling to remember?. Failing > > > >that, I could look at the very old patterns we used in the original > > > >HadCM3 simulation i.e. by Peter and I back in year 2000. > > > > > > > >I'm in CEH tomorrow morning after 10am if you want to ring. It's > > > >quite likely that you have not made an error, but in fact finding > > > >differences due to physics enhancement. > > > > > > > >All the best, > > > >Chris. > > > > > > > > > > > > > > > > > > > > > > > >Chris Huntingford > > > >Climate Change Modeller > > > >+44 (0)1491 692389 > > > >+44 (0)7884437138 > > > >Centre for Ecology and Hydrology, Benson Lane, Wallingford, OX10 8BB, U.K. > > > >[1]http://www.ceh.ac.uk/staffWebPages/DrChrisHuntingford.html > > > > > > > > >>> Deborah Hemming > > 03/03/2009 18:23 >>> > > > >Nigel, > > > > > > > > I'm currently checking with Tim and Chris to ensure that the patterns > > > >i'm producing with QUMP (using the ClimGen approach) are reasonable > > > >compared to those Tim has done already. > > > > > > > > Tim has made a comparison of the temperature patterns generated from > > > >the Standard run (HadCM3) from his code for ClimGen and mine using the > > > >QUMP standard run (basically similar to HadCM3 standard). We are > > > >concerned that my pattern was ~2C amplified in the N Polar region > > > >compared to Tim's ClimGen. Currently i'm running tests to diagnose > > > >where the problem/error may be and should have some answers on this over > > > >the next 2 days. > > > > > > > > I am very pushed for time and will be away for the following 2 weeks, > > > >so think it will be more worthwhile if I spend Thursday trying to sort > > > >this out rather than attend the meeting. Hope that doesnt cause any > > > >problems. I will update you on the latest at end of day tomorrow. > > > > > > > >Cheers, > > > >Debbie. > > > > > > > >On Tue, 2009-03-03 at 14:37 +0000, Nigel Arnell wrote: > > > > > Debbie / Tim, > > > > > > > > > > Will you be able to update us on the status of the QUMP/ClimGen > > > > > scenarios on Thursday? > > > > > > > > > > Thanks > > > > > > > > > > Nigel > > > > > > > > > > > > > > > Professor Nigel Arnell > > > > > Director > > > > > Walker Institute for Climate System Research > > > > > University of Reading > > > > > Earley Gate > > > > > RG6 6BB > > > > > UK > > > > > > > > > > +44-118-378-7392 > > > > > [2]www.walker-institute.ac.uk > > > > > > > > > > > > > > > > > > >-- > > > >Dr Deborah Hemming (Manager, Climate Impacts Analysis) > > > >Met Office Hadley Centre for Climate Change > > > >Fitzroy Road Exeter Devon EX1 3PB > > > >tel: +44 (0)1392 885715 fax: +44 (0)1392 885681 > > > >web: [3]http://www.hadleycentre.co.uk > > > > > > > > > > > >-- > > > >This message (and any attachments) is for the recipient only. NERC > > > >is subject to the Freedom of Information Act 2000 and the contents > > > >of this email and any reply you make may be disclosed by NERC unless > > > >it is exempt from release under the Act. Any material supplied to > > > >NERC may be stored in an electronic records management system. > > > > > > Dr Timothy J Osborn, Academic Fellow > > > Climatic Research Unit > > > School of Environmental Sciences > > > University of East Anglia > > > Norwich NR4 7TJ, UK > > > > > > e-mail: t.osborn@uea.ac.uk > > > phone: +44 1603 592089 > > > fax: +44 1603 507784 > > > web: [4]http://www.cru.uea.ac.uk/~timo/ > > > sunclock: [5]http://www.cru.uea.ac.uk/~timo/sunclock.htm > > > > > > > >-- > >Dr Deborah Hemming (Manager, Climate Impacts Analysis) > >Met Office Hadley Centre for Climate Change > >Fitzroy Road Exeter Devon EX1 3PB > >tel: +44 (0)1392 885715 fax: +44 (0)1392 885681 > >web: [6]http://www.hadleycentre.co.uk > > Dr Timothy J Osborn, Academic Fellow > Climatic Research Unit > School of Environmental Sciences > University of East Anglia > Norwich NR4 7TJ, UK > > e-mail: t.osborn@uea.ac.uk > phone: +44 1603 592089 > fax: +44 1603 507784 > web: [7]http://www.cru.uea.ac.uk/~timo/ > sunclock: [8]http://www.cru.uea.ac.uk/~timo/sunclock.htm > > -- Dr Deborah Hemming (Manager, Climate Impacts Analysis) Met Office Hadley Centre for Climate Change Fitzroy Road Exeter Devon EX1 3PB tel: +44 (0)1392 885715 fax: +44 (0)1392 885681 web: [9]http://www.hadleycentre.co.uk