cc: Mike Mann date: Wed, 21 Feb 2001 08:54:41 +0800 from: Scott Rutherford subject: Re: verification results to: Tim Osborn 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.osborn@uea.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 srutherford@virginia.edu srutherford@gso.uri.edu phone: (804) 924-4669 (401) 874-6599 fax: (804) 982-2137 (401) 874-6160