date: Tue Apr 15 14:54:23 2008
from: Keith Briffa <k.briffa@uea.ac.uk>
subject: Re: CRU TS3.0
to: Gerard van der Schrier <schrier@knmi.nl>

   Gerard
   First - will you do the first pass at the paper correction - I agree that not that
   difficult as  first thought -  but see my previous comments.
   As for the PDSI and alternative use of Thornthwaite and Penmann-Monteith , I suggested
   before that this test is perhaps best done using a selection of station tests, selected
   from "representative regions" where data exist that allow both to be calculated and perhaps
   where more direct measures of soil water state exist. I take your point about the
   "calibration" period correcting for some differences , but it is perhaps more valid to
   worry about the use of Thornthwaite in the first place - there are earlier reviews saying
   that this is not a good method is certain parts of  the world - and this links to your
   other point re the validity of PDSI or scPDSI in areas of permafrost , heavy snow/lie and
   very dry areas. Certainly some comparison at sites where actual soil water is directly
   monitored (Robock Russian work) , surely some sites in US and UK would be available here ?
   However , the main reason is to explore this and reassess Dai ( criticizing those areas
   that are invalid for whatever reasons) - and the IPCC map that shows drought world wide
   (PC1) see attached - did this get into the final report , I need to check. Happy you are
   still going this way and of course would like to be involved . Ditto that you are happy to
   work on  the 1000-year oak -based reconstruction - centred on Northwest Europe. We will
   process the oak data and get back to you on this soon.
   cheers
   Keith
    At 10:24 15/04/2008, Gerard van der Schrier wrote:

     Keith,
     I've agreed with Ed that I do the PDSI calculations and do some additional quality
     control tests. Harry will probably keep me updated when he finds more problems with the
     data.
     About the Int.J.Clim. paper: I've gone through the remarks you made and which you send
     me. There are some issues the referees raised, like the infilling of data, which are
     solved easily. We just have to put more emphasis on the remark we made that infilling is
     only used for T, the places where P is infilled are flagged as absent and not used in
     the analysis. I expect that other points are (nearly) as easy.
     About the Dai paper and other plans with PDSI: the idea is to see if the
     self-calibrating PDSI is changed dramatically if Penman-Monteith is used rather than
     Thornthwaite, and i'd like to see a comparison using a complicated and the simple
     waterbalance model as well. We've discussed this earlier and we don't expect any
     problems here simply due to the calibrating which probably "adjusts" for any problems
     with potential evapotranspiration. This should make one paper.
     The next paper is a global dataset based on the updated CRU data - the rework of Dai's
     paper. Now that we discuss this topic: I guess we may have problems in regions like the
     Sahara or Siberia - any ideas yet? We could wait and see how the scPDSI behaves, but is
     the PDSI a valid index for these regions anyway?
     Cheers, Gerard

     Gerard
     do you wish me to chase this up ? Also can you update me on the Int.J.Clim paper status.
     Are you considering a rework of the Dai global paper ? Cheers
     Keith
     At 08:38 14/04/2008, you wrote:

     Hi Harry,
     Sorry to bother you again about the CRU updated data.
     Ed Cook and myself were wondering about the status of the CRU TS 3.0 data. Is it ready
     or not yet? We are slightly confused about the status of this update.
     Some time ago, I received an ftp address for this data and I downloaded the data (both
     Temp - tx, tg, tn- and Precip). But later, I learned that CRU withdrew support for these
     data - so I stopped working with these data.
     Can you tell me where (which continents or which time periods) you suspect most in the
     dataset I downloaded? (downloaded it at the end of September last year). Or would you
     advise me not to use the data at all before there is a properly tested dataset?
     Cheers, Gerard
     --
     ----------------------------------------------------------
     Gerard van der Schrier
     Royal Netherlands Meteorological Institute (KNMI)
     dept. KS/KA
     PO Box 201
     3730 AE De Bilt
     The Netherlands
     schrier@knmi.nl
     +31-30-2206597
     [1]www.knmi.nl/~schrier
     ----------------------------------------------------------

     --
     Professor Keith Briffa,
     Climatic Research Unit
     University of East Anglia
     Norwich, NR4 7TJ, U.K.
     Phone: +44-1603-593909
     Fax: +44-1603-507784
     [2]http://www.cru.uea.ac.uk/cru/people/briffa/

     --
     ----------------------------------------------------------
     Gerard van der Schrier
     Royal Netherlands Meteorological Institute (KNMI)
     dept. KS/KA
     PO Box 201
     3730 AE De Bilt
     The Netherlands
     schrier@knmi.nl
     +31-30-2206597
     [3]www.knmi.nl/~schrier
     ----------------------------------------------------------

   --
   Professor Keith Briffa,
   Climatic Research Unit
   University of East Anglia
   Norwich, NR4 7TJ, U.K.

   Phone: +44-1603-593909
   Fax: +44-1603-507784
   [4]http://www.cru.uea.ac.uk/cru/people/briffa/

