Sunday, June 10, 2012

5048.txt

cc: Mike Mann <mannatXYZxyzginia.edu>
date: Wed, 21 Feb 2001 08:54:41 +0800
from: Scott Rutherford <srutherfordatXYZxyzginia.edu>
subject: Re: verification results
to: Tim Osborn <t.osbornatXYZxyz.ac.uk>

Dear Tim,

First, I put together a new results page at
http://holocene.evsc.virginia.edu/~rutherfo/results. The page has a
plot of northern hemisphere mean temperature for each run and a link
to more detailed plots and the annual maps. Note that there is a link
at the top of the page for the first 1400-1856 reconstruction using
the mxd data and compared to the Mann et al. reconstruction. This is
for the annual mean and uses 366 mxd proxies. I don't use all 387
becuase there are some that don't reach 1856 and trying to fill these
missing values increases the run time by several orders of magnitude.
Other 1400-1856 reconstructions are running.

Regarding the MXD errors. It would be nice to have them, but I view
that as a minor point and your time is probably better spent
elsewhere seeing as they are not easy to get.

I will work on calculating the variance sums over only available
temperature values if you want to do the mxd gridpoint comparisons.

Also, if you have a minute I could use some IDL help. I have an IDL
data file that I don't know what to do with (since I don't know a
thing about IDL). Would you be willing to convert it to something I
can deal with (matlab, netCDF, ascii)? The data file is global
oceanic primary production.

Regards,

Scott


>Dear Scott and Mike,
>
>sorry for the lack of response to your e-mail in January. I've been away
>quite a bit and then had three proposal deadlines come up last week, so was
>rather busy. The results look *very* promising, with good verification
>statistics etc. The multivariate resolved variance is only slightly higher
>for the warm season than for the cold season which is a little surprising,
>though I guess warm & cold seasons are more strongly correlated for the
>leading covariance structures that are most highly weighted than for the
>smaller scale variations that are suppressed. A couple of specific things:
>
>(1) MXD errors. A really useful measure that one can use here is the EPS
>(Expressed Population Signal), based on the mean correlation between the
>tree cores that make up each chronology (rbar), and the number of tree
>cores (n). Time-dependence can be included by putting the time-varying
>number of tree cores into the EPS equation. This would give some measure
>of the 387 chronologies. For the gridded case, some improvement would have
>to be estimated for the many grid boxes that contain >1 chronology, but
>that's not difficult to do. What is *difficult* is that I don't have
>either rbar or n for each chronology! All I have is, for each year and
>each chronology, the number of tree cores with data expressed as a fraction
>of the maximum number of tree cores for that chronology, i.e.,
>fraction(x,t) = n(x,t) / nmax(x). Since I don't know nmax for each
>chronology x, I can't work out n(x,t) from fraction(x,t). Nor do I know
>rbar(x). I've been wanting to get rbar(x) and n(x,t) ever since I started
>using this tree-ring data set (1997), but it's apparently not easily
>available. How important do you think it is for the current piece of work?
> If it is important then I could try to get it again, but if it's a fairly
>minor side issue then I won't.
>
>(2) From what I remember about the plan of action, the idea was to do these
>first runs using the already infilled instrumental data (though of course
>witheld for the pre-1901 period). I assume, therefore, that the timeseries
>and statistics shown are from this infilled & complete data set (I see now
>from the annual maps that this *is* the case because the "raw data" maps
>are complete). It would be useful to compare these MXD-based
>reconstructions with the instrumental data by sampling only those grid
>boxes in both the raw and reconstructed fields that originally contained
>real data in the instrumental data set. [I assume that the infilled
>instrumental data will be the same as the original instrumental data for
>these grid boxes.] The comparisons/statistics shown are useful, but only
>in addition to the comparison done against the (subsampled) original data,
>because (i) the message is harder to get across when using already infilled
>data; and (ii) the statistics *might* be slightly (artificially) improved
>when using infilled data. If you'd prefer me to do this, then let me know
>where the data sets are (plus format) and I can compare against my copy of
>the Jones instrumental data.
>
>So I guess that you should have enough to talk about at the EGS in Nice
>then Mike? Please let me know if you need any further input from me at
>this stage.
>
>Best regards to you both,
>
>Tim
>
>
>
>
>
>Dr Timothy J Osborn | phone: +44 1603 592089
>Senior Research Associate | fax: +44 1603 507784
>Climatic Research Unit | e-mail: t.osbornatXYZxyz.ac.uk
>School of Environmental Sciences | web-site:
>University of East Anglia __________| http://www.cru.uea.ac.uk/~timo/
>Norwich NR4 7TJ | sunclock:
>UK | http://www.cru.uea.ac.uk/~timo/sunclock.htm

--
______________________________________________
Scott Rutherford

University of Virginia University of Rhode Island
Environmental Sciences Graduate School of Oceanography
Clark Hall South Ferry Road
Charlottesville, VA 22903 Narragansett, RI 02882
srutherfordatXYZxyzginia.edu srutherfordatXYZxyz.uri.edu
phone: (804) 924-4669 (401) 874-6599
fax: (804) 982-2137 (401) 874-6160

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