Thursday, April 12, 2012

3352.txt

date: Tue Mar 24 10:59:17 2009
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: Northern Latitude differences
to: Deborah Hemming <debbie.hemmingatXYZxyzoffice.gov.uk>

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 <debbie.hemmingatXYZxyzoffice.gov.uk>
> > 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.osbornatXYZxyz.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.osbornatXYZxyz.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

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