cc: Beck Christoph <christoph.beck@dwd.de>, Rudolf Bruno <Bruno.Rudolf@dwd.de>
date: Tue May  3 08:25:41 2005
from: Phil Jones <p.jones@uea.ac.uk>
subject: Re: AW: Your views appreciated
to: Grieser Jrgen <juergen.grieser@dwd.de>

    Jurgen, Bruno and Christoph,
      Thanks for the comments. The'll be discussed at the WGI IPCC meeting next week
    (May 10-12).
    Cheers
    Phil
   At 16:42 29/04/2005, Grieser Jrgen wrote:

     Dear Phil,
     Bruno forwarded your todays email to me and I am very glad to be asked to
     reply.
     Pls find my comments in the attached word document.
     In case of further questions, comments, etc. pls don't hesitat to contact me
     again.
     Best regards from Christoph Beck, Bruno Rudolf and myself,
     Jrgen.

     ********************************************
     Dr. Juergen Grieser
     Global Precipitation Climatology Centre GPCC
     Deutscher Wetterdienst
     P.O.Box 10 04 65
     63004 Offenbach
     Germany
     Tel.: +49 -69 8062 2873
     Fax:  +49 -69 8062 3759
     Web: [1]http://gpcc.dwd.de <[2]http://gpcc.dwd.de/>
     ********************************************


      -----Ursprngliche Nachricht-----
     Von: Rudolf Bruno
     Gesendet am: Freitag, 29. April 2005 13:39
     An: 'Phil Jones'
     Cc: Grieser Jrgen
     Betreff: AW: Your views appreciated
     Hi Phil,

     thank you for contacting us.  A very first quick reply:
     Yes,  what you called the fixed stations versions should be used for the
     purpose discussed.
     We call it 50 year climatology, because it is optimized for homogeneity, and
     it is THE only of our products recommended to use it for climate variability
     (trend) studies. And relative anomaly is used for interpolation for this
     product.

     Juergen Grieser will send a more complete reply on the 50 year climatology.

     The Monitoring Product and Full Data Product are based on interpolation of
     precipitation totals because we had no normals for many of the stations with
     data for the recent years. For the recent years, most data are only
     available from SYNOP, and the accuracy of those is very low. Compared to
     normals, we partly obtain unrealistic anomalies, which are spatially
     exported by gridding. Maps resulting from the anomaly maps combined with
     normal maps showed some curious structures, whil the results from direct
     interpolation was still plausible. This assessment is based on earlier
     studies. We will do the methods comparison again for the currebt version of
     the full data basis.

     But whatever one does in analysis: if the gauge data base (number of
     stations) is very different in time, one will not get a homogeneous product
     (my opinion).

     Cheers,
     Bruno


      -----Ursprngliche Nachricht-----
     Von: Phil Jones [[3]mailto:p.jones@uea.ac.uk]
     Gesendet am: Freitag, 29. April 2005 11:16
     An: Rudolf Bruno
     Betreff: Your views appreciated
      Bruno,
          Shortly after AOPC, I was back with my IPCC hat on modifying text based
     on
      reviews of our first zero-order draft. I go to Beijing the week after next
     for the next
      Lead Author's meeting. By mid-August, we will have a new draft (the
     first-order one)
      which can be downloaded by anyone over an 8-week period then. I expect many
      hundreds will and there will be thousands of comments. That was some
     background !
          I sent your email about VasClimO to some of the people we've involved
     as contributing
      authors (CAs) and also to our Lead Author for our precipitation section.
     Our LA for this is
      Dave Easterling. The details also went to Aiguo Dai (who is with Kevin
     Trenberth at NCAR).
      My intention was to alert this group to your latest work at GPCC. I said
     that your dataset
      from 1951 was likely the best available. Our chapter currently has trend
     maps for
      1901-2004 and 1979-2004 from GHCN gridded fields (Dave Easterling produced
     these).
      Dave hasn't responded on this yet.
           The point of this email is to get your views on the email below from
     Aiguo Dai.
      We will almost certainly have some time series plots from different data
     sources
      including GPCC, GHCN, maybe CRU and Chen et al.. What I would like before I
      leave for China on May 7 (so by middle of next week) are your brief views
     on some
      of these other products (e.g. Chen et al. 2002, GPCPv2 from Adler et al.,
     2003)?
           Would you recommend using your fixed station version?
        I am very sympathetic to the view that you should grid using anomalies.
     Can you briefly
      say why you didn't?  If the answers to all these questions are in the
     report, tell me
      and I'll read it. I've not had time to yet.
         I am just trying to get all the views together for the Beijing meeting.
     I expect Kevin
      Trenberth will want to accept what Aiguo says. For the moment, just reply
     to me.
      Cheers
      Phil
     Date: Thu, 28 Apr 2005 16:17:07 -0600
     From: Aiguo Dai <adai@cgd.ucar.edu>
     Organization: NCAR, Boulder, CO
     User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4)
     Gecko/20030624 Netscape/7.1 (ax)
     X-Accept-Language: en-us, en
     To: Phil Jones <p.jones@uea.ac.uk>
     CC: trenberth@ucar.edu, Peter Ambenje <omash01@yahoo.com>,
        Roxana Bojariu <bojariu@b.astral.ro>,
        David Easterling <david.Easterling@noaa.gov>,
        David Parker <david.parker@metoffice.gov.uk>,
        Fatemeh Rahimzadeh <rahim_f@irimet.net>, Jim Renwick
     <j.renwick@niwa.co.nz>,
        Matilde Rusticucci <mati@at.fcen.uba.ar>,
        Brian Soden <bsoden@rsmas.miami.edu>, Panmao Zhai <pmzhai@cma.gov.cn>,
        Albert Klein Tank <Albert.Klein.Tank@knmi.nl>,
        Aiguo Dai <adai@cgd.ucar.edu>
     Subject: Re: Fwd: News about GPCC
     X-Spam-Score: 1.3
     X-Spam-Level: +
     Dear Phil et al.:
     Based on my reading of their tech, report, GPCC is still gridding the total
     monthly precipitation amounts
     instead of anomalies. Many people (e.g., Jones and Hulme 1996; Chen et al.
     2002) have shown that
     it is much better to grid the anomalies besides different gridding methods,
     even for temperature.
     GPCC argues that gridding monthly anomalies is better for some regions but
     worse for other regions,
     which I can not understand.
     Because of this griding method, one can not use their version 3 full data
     product for assessing climate
     changes (because addition or removal of wet/dry stations will have large
     impacts on regional estimates
     of precipitation), while their version with fixed stations (9343, but still
     10% of the years may have missing
     data) does not make full use of the available data. For example Chen et al.
     (2002) and GHCHv2 use more than
     10,000 gauges from 1948-around 1993 (over 15,000 during the 1960s and
     1970s). I strongly recommend GPCC
     to grid anomalies using all available gauge data for each month. Maybe they
     can listen to people like Phil?
     There appears to be large differences among various estiamtes for global
     (land) precipitation for the last
     several years (1997-present), partly because of limited number of raingages
     available. The attached figure
     compares land precip during 1979-2002 from Chen et al. (2002), CRU (New et
     al., Mitchell et al.) and GPCP v2
     (Adler et al. 2003, with climatological corrections for wind-induced
     undercatch). I think it would be useful to
     add both the Chen et al.  (1948-present) and the new GPCC (1951-2000, the
     fixed station version) analyses
     into the precip plots of IPCC chapter 3.
     Regards,
     Aiguo Dai
     Prof. Phil Jones
     Climatic Research Unit        Telephone +44 (0) 1603 592090
     School of Environmental Sciences    Fax +44 (0) 1603 507784
     University of East Anglia
     Norwich                          Email    p.jones@uea.ac.uk
     NR4 7TJ
     UK
     ----------------------------------------------------------------------------

   Prof. Phil Jones
   Climatic Research Unit        Telephone +44 (0) 1603 592090
   School of Environmental Sciences    Fax +44 (0) 1603 507784
   University of East Anglia
   Norwich                          Email    p.jones@uea.ac.uk
   NR4 7TJ
   UK
   ----------------------------------------------------------------------------

