[RegCNET] Max cloud fraction

[Travis O'Brien]

Hi Alex,

>From what I understand, this value was chosen several years ago during the
model tuning stage for either a European domain or African domain
simulation (I can't recall which).  I'm not aware of any reference
regarding this choice.  I think this choice is justifiable if one assumes
that most clouds are smaller than a model grid cell.

However, a relatively recent paper (Wood and Field, 2011; J. Clim) shows
that the number of clouds larger than ~200 km size is approximately equal
to the number of clouds smaller than ~200 km size, so I wonder if this
parameter choice (and associated small-cloud assumption) should be
revisited.

Kind Regards,
-Travis-


On Tue, Jun 3, 2014 at 2:13 PM, Alexander Bryan <ambrya at umich.edu> wrote:

> Hi RegCNet,
>
> Could someone point me to a reference that explains where the default
> value for maximum cloud fraction (cftotmax = 0.75) comes from? Does this
> cap mean that the cloud fraction output variable (totcf) does not allow for
> overcast skies? Can this variable be reliably used as input for a lake
> circulation model?
>
> Alex Bryan
> Ph.D. Candidate
> Department of Atmospheric, Oceanic, and Space Sciences
> University of Michigan, Ann Arbor, MI
> Email: ambrya at umich.edu
> URL: http://aoss.engin.umich.edu/people/ambrya
>
>
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-- 
Travis O'Brien
Research Scientist, Earth Sciences Division
Lawrence Berkeley National Lab
http://esd.lbl.gov/about/staff/travisobrien/
<http://esd.lbl.gov/about/staff/travisobrien/index.html>
(510) 495-8047
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