Subject: Re: using sea ice concentration as forcing
From: Peter Paul Smolka (smolka@uni-muenster.de)
Date: Thu Nov 29 2001 - 07:52:02 MST
On Wed, 28 Nov 2001, David Noone wrote:
> Date: Wed, 28 Nov 2001 15:55:18 -0800 (PST)
> From: David Noone <dcn@gps.caltech.edu>
> To: Peter Paul Smolka <smolka@uni-muenster.de>
> Cc: Qiaozhen Mu <qiaozhen@utig.ig.utexas.edu>, ccm-users@UCAR.EDU
> Subject: Re: using sea ice concentration as forcing
>
>
> > > Now I want to do some simulations with CCM3.10, using sea ice
> > > concentration as input data, which means I don't want the model to
> > > calculate sea ice, but let it run under the force of sea ice. Now
> > > the question is how I can input the sea ice file?
>
> <snip>
>
> > 3) Locate the Oro= .... AND other variables.
> <snip>
> > 6) Take the time variant boundary dataset (if I remember on the
> > spot correctly): Apply the same Ascii procedure.
> >
> > Set at the appropriate data-points the temperature to -1.8.
>
> <snip>
>
> Be careful to recognize that using the DOM, ORO sets only the mask, and
> not the concentration per se. In fact, CCM3.6 does not include a
> parameterisation to consider the open water fraction of the ice pack.
> Instead, the oro=2 (for sea ice) flag says "this ocean grid box is
> covered in sea ice with a concentration of 100% and a thickness (sicthk)
> of 2 meters". So in fact, it doesn't "calculate" the sea ice, it just
> reads in temperature from the boundary data set and sets it as ice if
> it's cold enough (flagged as ts < tsice, as Peter mentions in his step
> 6). I suppose you would define this mask based on your concentration
> data.
Dear David,
my posting referred to exactly this question: "How to specify an
orography (including sea-ice) where each data-point is for a 100%
either land, ocean or ice."
The atmosphere (in the DOM version) is the result of the driving
conditions (SSTs, sea-ice, etc.).
For Pliocene, Miocene and other greenhouse conditions (both
Cretaceaous and warm interglacials) specifying the boundary conditions
at 128x64 resolution is a challenge (for example necessary knowledge
about the sea-ice coverage of the Arctic Ocean before 2.6 m.y.).
Knowledge about
fractions of sea-ice at each data-point as well as knowledge about
fluxes reflecting also the different nature of sea-ice (formed under
calm or stormy conditions etc.) is (at least today) beyond
geological possibilities (at least for Pliocene, Miocene and older
times)
Tasks are of course self-organizing models that will be able
to run 3 My transiently (to reproduce also details of for example
icecore data correctly).
Reason: If we are able to reproduce the past 3-5 m.y. correctly
(transiently) then we are
regarding climate change studies on the safe side
(= sudden surprises are then unlikely).
>
> To include the concentration itself, you will need to modify the source
> to take account of both the ice covered part and the open water parts of
> the ocean grid boxes. The easiest way might be you will need to call
(...)
>
> Cheers,
>
> David
>
Best regards, Peter
**********************************************************************
Dr. Peter P. Smolka
University Muenster
Geological Institute
Corrensstr. 24
D-48149 Muenster
Tel.: +49/251/833-3989 +49/2533/4401
Fax: +49/251/833-3989 +49/2533/4401
E-Mail: smolka@uni-muenster.de
E-Mail: PSmolka@T-Online.de
**********************************************************************
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