Tuesday, April 3, 2012


cc: Keith Briffa <k.briffaatXYZxyz.ac.uk>
date: Fri, 20 May 2005 05:36:23 -0400 (EDT)
from: Alan Robock <robockatXYZxyzsci.rutgers.edu>
subject: Re: your presentation at EGU
to: Gerard van der Schrier <g.schrieratXYZxyz.ac.uk>

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Dear Gerard,

Thanks for your interesting results. I guess I would conclude that you
have discovered limitations to the PDSI model that raise questions as to
how well it simulates long-term trends. It means, I think, that more
information than temperature and precipitation are needed for such
calculations. It makes me wonder how good tree-ring reconstructions of
drought are that are based only on PDSI.

(remove 0 when calling from
On sabbatical, Jan. 20 - June 30, 2005, at outside France)
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Alan Robock, Professor II
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On Fri, 20 May 2005, Gerard van der Schrier wrote:

> Dear Alan,
> Thanks very much for the suggestions to improve the presentation. I agree
> that the quality of the slides were horrible. It all seemed o.k. when I
> produced them at the office though.
> Unfortunately, I've missed the opportunity to shake hands during the coffee
> break. What I would have liked to say is that I really liked your recent GRL
> article and the presentation at the EGU meeting. The absence of a trend
> toward increased summer drought we observe in our PDSI records, was nice to
> see confirmed in your soil moisture records form the Ukraine.
> Following a suggestion made by somebody in the audience, I computed the
> self-calibrating PDSI for the area in the Ukraine from which you have the
> records of soil moisture data. (June-July-August, averaged over 22-40E,
> 46-52N) The figure is attached to this mail, and it shows a clear trend from
> the mid-1940s to the early 1980s toward increased availability of soil
> moisture. This is similar to your fig. 2a. However, instead of remaining
> more-or-less constant from the mid 1980s onwards, the PDSI shows a rather
> abrupt transition to slightly dry conditions and remains more-or-less
> constant until 2002 (perhaps with a slight trend towards wetter conditions).
> (alanrobock.eps)
> When averaging the CRU temperature and precipitation datasets over the same
> area (for the preceeding JFMAMJJA months), a similar trend toward wetter
> conditions in precipitation is found as in your figure 2b. From the early
> 1980s, there is a steep trend toward less precipitation, coupled to
> persistent and very high temperatures, which explains the change in the
> scPDSI curve. (alanrobock2.eps)
> Best Regards,
> Gerard
> ---------------------------------------
> Dr. G. van der Schrier
> Climatic Research Unit
> University of East Anglia
> Norwich NR4 7TJ
> UK
> g.schrieratXYZxyz.ac.uk
> www.uea.ac.uk/~f029
> ---------------------------------------

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