Saturday, June 9, 2012

4970.txt

cc: Ben Santer <santer1atXYZxyzl.gov>, Susan Solomon <Susan.SolomonatXYZxyza.gov>, John Lanzante <John.LanzanteatXYZxyza.gov>, Melissa Free <melissa.freeatXYZxyza.gov>, Dian Seidel <dian.seidelatXYZxyza.gov>, Tom Wigley <wigleyatXYZxyz.ucar.edu>, Karl Taylor <taylor13atXYZxyzl.gov>, Thomas R Karl <Thomas.R.KarlatXYZxyza.gov>, Carl Mears <mearsatXYZxyzss.com>, "David C. Bader" <bader2atXYZxyzl.gov>, "'Francis W. Zwiers'" <francis.zwiersatXYZxyzgc.ca>, Frank Wentz <frank.wentzatXYZxyzss.com>, Leopold Haimberger <leopold.haimbergeratXYZxyzvie.ac.at>, "Michael C. MacCracken" <mmaccracatXYZxyzcast.net>, Phil Jones <p.jonesatXYZxyz.ac.uk>, Steve Sherwood <Steven.SherwoodatXYZxyze.edu>, Tim Osborn <t.osbornatXYZxyz.ac.uk>, Gavin Schmidt <gschmidtatXYZxyzs.nasa.gov>, "Hack, James J." <jhackatXYZxyzl.gov>
date: Tue, 22 Jan 2008 09:46:49 +0000
from: Peter Thorne <peter.thorneatXYZxyzoffice.gov.uk>
subject: Re: The minus 1 (.png or .ps.gz)
to: Stephen Klein <klein21atXYZxyzl.gov>

On Thu, 2008-01-17 at 14:17 -0800, Stephen Klein wrote:
> Peter et al.,
>
> Thanks for this figure updating Santer et al. 2005. Although I am a
> bit rusty on this subject, there are two questions I have:
>
> 1) Does anybody have an explanation why there is a relative minimum
> (and some negative trends) between 500 and 700 hPa? No models with
> significant surface warming do this, and I can't think of a plausible
> physical reason for this. Do people feel the relative cooling of this
> layer relative to the surface is robust?
>

As Steve Sherwood has already said I don't think this result is
necessarily robust. Certainly some of the solutions that the automated
version of HadAT comes up with do not include such a feature (although
the majority still do).

If it is real then this region is both near the freezing point and the
cut off of shallow convection. So there are possible strawman argument
reasons relating to either:
1. A changing relative freq of shallow and deep convection or;
2. That at this point we may see no trend because of the thermal
properties of water near its triple-point.

These are both very much strawman hypotheses. I have no idea how we
would test either of them. Nor do I think we should at this stage. But
if anyone wants to take it forward I'll be more than happy to help as I
can.


> 2) Have you thought of producing a comparison of models to radiosonde
> observations for a longer term trend (late 1950s to 1999)? My
> recollection (from when I worked with John L. and Dian S.) is that
> the tropical radiosonde upper troposphere temperature trends were a
> bit stronger over the longer-term. Even if you add this to the paper,
> it might be nice to examine a figure of this type for the longer
> period to assess models, and perhaps comment on in the paper.

I can produce such a figure tomorrow if there is general wish to see it,
but as Steve says this longer period does show much more the expected
profile behaviour in general, at least for RATPAC-A and HadAT. Perhaps
it is another case of cherry-picking in Douglass et al that we would
like to highlight and it does tie in with the recent GRL paper that
showed choice of period was important in whether a discrepancy existed
or not ...

Peter
--
Peter Thorne Climate Research Scientist
Met Office Hadley Centre, FitzRoy Road, Exeter, EX1 3PB
tel. +44 1392 886552 fax +44 1392 885681
www.metoffice.gov.uk/hadobs

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