Wednesday, May 23, 2012

4603.txt

date: Fri, 15 Feb 2008 08:55:32 -0700
from: Aiguo Dai <adaiatXYZxyzr.edu>
subject: Re: A paper you're doing
to: Phil Jones <p.jonesatXYZxyz.ac.uk>

Phil,
In Dai (2006, J. Clim), I specifically examined the changes in global (both ocean and land)
surface q and RH
from 1975-2005 and found that sfc q increases with air temperature while RH remains fairly
constand (except
a few regions in India and the central US where RH increased). Since surface water/latent
heat flux is affected, in part, only by
RH, not q itself, the changes in surface humidity should not be a major contributor to
changes in evaporation.
At the last Fall AGU meeting, I showed some prelimiary results on trends in surface wind
speed over the globe during
the last 30 yrs or so. The sfc obs. show an apparent decreasing trend in surface wind speed
over most of the Eurasia,
N.A. and other land areas. Although this is consistent with decreasing pan evaporation, I
am still trying to make sure the
wind data are not showing nonclimatic changes.
Aiguo
Phil Jones wrote:

Aiguo,
Thanks. It wasn't me slowing the ms down!
Another factor in addition to wind and radiation is vapour pressure.
In case you've not seen the attached here it is. Vapour Pressue and q are
going up as T goes up. RH stays much the same.
We've submitted a longer paper on this dataset. It is rather short
though - only going back to 1973.

Cheers
Phil
At 16:49 14/02/2008, you wrote:

Hi Phil,
The manuscript is attached, which took a while to get through the review process, but
look like it will be
accepted after some revision.
The main conclusion is that changes in wind speed and sfc radiation may be important in
water balance
calculation for wet regions. Because the PDSI model considers only T and P changes, its
application over
wet, energy-limited regions may be questionable. We still need to work out this on a
global basis. On the
other hand, the PDSI results from Dai et al. (2004) illustrate the potential drying from
surface warming and
precip changes alone, and this drying appears to have happened over many regions (e.g.,
most Africa, etc.).
Aiguo
Phil Jones wrote:

Aiguo,

I hear you're doing a paper with Hobbins, Roderick and Farquhar.
Is it possible to send me a copy of this?
Cheers
Phil
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 [1]p.jones@uea.ac.uk
NR4 7TJ
UK
----------------------------------------------------------------------------


--
Aiguo Dai,
Scientist
Email: [2]adai@ucar.edu
Climate & Global Dynamics
Division
Phone: 303-497-1357
National Center for Atmospheric Research
Fax : 303-497-1333
P.O. Box 3000, Boulder, CO 80307,
USA
[3]www.cgd.ucar.edu/cas/adai/
Street Address: 1850 Table Mesa Drive, Boulder, CO 80305, USA

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 [4]p.jones@uea.ac.uk
NR4 7TJ
UK
----------------------------------------------------------------------------

--
Aiguo Dai, Scientist Email: [5]adai@ucar.edu
Climate & Global Dynamics Division Phone: 303-497-1357
National Center for Atmospheric Research Fax : 303-497-1333
P.O. Box 3000, Boulder, CO 80307, USA [6]www.cgd.ucar.edu/cas/adai/
Street Address: 1850 Table Mesa Drive, Boulder, CO 80305, USA

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