Tuesday, April 3, 2012

3152.txt

cc: Phil Jones <p.jonesatXYZxyz.ac.uk>, Thomas R Karl <thomas.r.karl@noaa.gov>, Kevin Trenberth <trenbertatXYZxyz.ucar.edu>
date: Tue, 24 Jun 2008 10:44:53 -0600
from: Aiguo Dai <adaiatXYZxyzr.edu>
subject: Re: ET and PDSI
to: trenbertatXYZxyzr.edu

Kevin,
Sorry to hear that. I tried to tone down the statements regarding the global implications
of the results, as
our CLM3-simulated soil moisture (forced by observed precip and temp, etc.) seems to
support the
conclusion based on our PDSI. The IPCC AR4 also shows (Fig. 10.12) that soil moisture will
become
drier at northern latitudes even though precip increases there. I think that the
calculations of surface evaporation,
runoff, soil moisture, and other land surface processes are much more sophisticated in
current global climate models
than in simple water balance models (like the Palmer model). Thus the climate model results
avoid most of the
issues dicussed by Hobbins et al. (e.g., related to ET calculation, effects of vegetation,
snow cover, changes in
humidity, radiation, and winds).
Regards,
Aiguo
Aiguo
Kevin Trenberth wrote:

Aiguo
I can't say that I like this paper at all.
Kevin


Hi, Phil,

Our GRL paper finally has come out. Below is the ref. and a link.

Best regards,

Aiguo

Hobbins, M. T., *A. Dai*, M. L. Roderick, and G. D. Farquhar, 2008:
*Revisiting potential evapotranspiration parameterizations as drivers of
long-term water balance trends. */Geophys. Res. Lett./, *35*, L12403,
doi:10.1029/2008GL033840 (Paper)
[1]<http://www.cgd.ucar.edu/cas/adai/papers/Hobbins_etal08-ET-PDSI.pdf>

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 [2]p.jones@uea.ac.uk
[3]<mailto:p.jones@uea.ac.uk>
NR4 7TJ
UK
----------------------------------------------------------------------------


--
Aiguo Dai,
Scientist
Email: [4]adai@ucar.edu [5]<mailto: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/ [7]<http://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 [8]p.jones@uea.ac.uk
NR4 7TJ
UK
----------------------------------------------------------------------------

--
Aiguo Dai, Scientist Email: [9]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 [10]www.cgd.ucar.edu/cas/adai/
Street Address: 1850 Table Mesa Drive, Boulder, CO 80305, USA


___________________
Kevin Trenberth
Climate Analysis Section, NCAR
PO Box 3000
Boulder CO 80307
ph 303 497 1318
[11]http://www.cgd.ucar.edu/cas/trenbert.html

--
Aiguo Dai, Scientist Email: [12]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 [13]www.cgd.ucar.edu/cas/adai/
Street Address: 1850 Table Mesa Drive, Boulder, CO 80305, USA

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