[MITgcm-support] cvelTimeScale
Riema Rachmayani
imoth_22 at yahoo.com
Mon Feb 5 02:32:13 EST 2007
dear all,
eta (elevation) at open boundaries is given and the simulation result is similar with the analitic solution, but i have problem for U (velocity) that seem not similar with the analitic solution, i describe U as orlanski at open boundaries, am i forgot something for orlanski setting??what should i do??
i describe cvelTimeScale=2000. (MIT default), is there formula for calculate cveltimescale in orlanski.F??
any to do with fracCVEL=deltaT/cvelTimeScale , fracCVEl=1.0 (turn off filtering) ??
is cvelTimeScale influence my simulation result??
thank you,
regards,
rima
----- Original Message ----
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Today's Topics:
1. Re: EVP stability (Matthew Mazloff)
2. Re: EVP stability (Jinlun Zhang)
3. Re: EVP stability (Dimitris Menemenlis)
4. Re: EVP stability (Matthew Mazloff)
5. Re: EVP stability (Patrick Heimbach)
6. Re: EVP stability (Dimitris Menemenlis)
----------------------------------------------------------------------
Message: 1
Date: Thu, 1 Feb 2007 19:10:37 -0500
From: Matthew Mazloff <mmazloff at MIT.EDU>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <1F75B412-60EB-4DF7-92A2-0C5F14D65E30 at mit.edu>
Content-Type: text/plain; charset=WINDOWS-1252; delsp=yes;
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Hi Dimitris,
As you said, for her EVP model Hunke used 30s time-step with grid
spacing 16km....at 1/6 deg. resolution my min spacing is
3.8km...about 1/4 this..so I tried 7.5 sec timesteps and the model
blew up on the third timestep. Very unstable. I have a 4x2 test
setup and I ran EVP fine on this so I don't think its a bug in the
configuration. Could it be possible that EVP is just not stable at
these resolutions? Any advice? Should I make a small high-
resolution test setup? Or does anyone else have one?
Thanks
-Matt
On Jan 27, 2007, at 9:36 AM, Dimitris Menemenlis wrote:
> Matt, stability criterion for EVP solver depends on internal ice
> pressure, strain rates, a damping parameter for the elastic waves,
> and other such things. So it's not easy to compute explicitly.
>
> In "Journal of Computational Physics 170, 18–38 (2001)", Elizabeth
> Hunke used a time step of 30 s for a domain with horizontal grid
> spacing of 16 km. So 45 s for your 1/6-deg domain seems too
> large. What is your smallest horizontal grid spacing, 4 km? I
> suggest that you try a 5-s to 10-s time step.
>
> Dimitris
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
------------------------------
Message: 2
Date: Thu, 01 Feb 2007 16:56:44 -0800
From: Jinlun Zhang <zhang at apl.washington.edu>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <45C28C4C.3010409 at apl.washington.edu>
Content-Type: text/plain; charset=windows-1252; format=flowed
Matt,
I don't have much experience with EVP, but here is a paper
http://www.mrcc.uqam.ca/V_f/Publications/articles/Saucier2004_ClimDyn.pdf,
that shows a time step of about 2 s for a resolution of 10km. So perhaps
you could try a smaller dt for your 3.8km grid. Another way to test
whether resolution is an issue is to go to the model to artificially
enlarge the grid size, while not changing anything else.
Jinlun
Matthew Mazloff wrote:
> Hi Dimitris,
>
> As you said, for her EVP model Hunke used 30s time-step with grid
> spacing 16km....at 1/6 deg. resolution my min spacing is
> 3.8km...about 1/4 this..so I tried 7.5 sec timesteps and the model
> blew up on the third timestep. Very unstable. I have a 4x2 test
> setup and I ran EVP fine on this so I don't think its a bug in the
> configuration. Could it be possible that EVP is just not stable at
> these resolutions? Any advice? Should I make a small high-
> resolution test setup? Or does anyone else have one?
>
> Thanks
> -Matt
>
>
>
>
> On Jan 27, 2007, at 9:36 AM, Dimitris Menemenlis wrote:
>
>> Matt, stability criterion for EVP solver depends on internal ice
>> pressure, strain rates, a damping parameter for the elastic waves,
>> and other such things. So it's not easy to compute explicitly.
>>
>> In "Journal of Computational Physics 170, 18–38 (2001)", Elizabeth
>> Hunke used a time step of 30 s for a domain with horizontal grid
>> spacing of 16 km. So 45 s for your 1/6-deg domain seems too large.
>> What is your smallest horizontal grid spacing, 4 km? I suggest that
>> you try a 5-s to 10-s time step.
>>
>> Dimitris
>
------------------------------
Message: 3
Date: Thu, 01 Feb 2007 18:29:02 -0800
From: Dimitris Menemenlis <menemenlis at sbcglobal.net>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <45C2A1EE.1090508 at sbcglobal.net>
Content-Type: text/plain; charset=windows-1252; format=flowed
Matt, I don't know what to say beyond Jinlun's suggestion. If you tried a 1s
time step and if it blew up right away, you would know that something else is
wrong. It is a big domain to be trying all these experiments blindly.
Maybe what you should do for time being, if you don't want to experiment, is to
go back to B-grid with LSR and with no ice-to-ocean connection. That
configuration worked on the 1/8th and on the 1/16th-degree global grids.
D.
------------------------------
Message: 4
Date: Thu, 1 Feb 2007 22:12:59 -0500
From: Matthew Mazloff <mmazloff at MIT.EDU>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <D7BFCB29-EB37-42C8-8AB2-FABADAE2045D at mit.edu>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Hi,
Thanks for the advice. I think I will make a small 1/6 degree
resolution test box and try running. Until then I want to just run
without dynamics. I am now using C-grid. For ice-covered areas, how
is the wind-stress transferred to the ocean if sea-ice dynamics are
off. Will there be no wind-stress...or will it go right through? Do
I have any options?
Thanks,
Matt
On Feb 1, 2007, at 9:29 PM, Dimitris Menemenlis wrote:
> Matt, I don't know what to say beyond Jinlun's suggestion. If you
> tried a 1s time step and if it blew up right away, you would know
> that something else is wrong. It is a big domain to be trying all
> these experiments blindly.
>
> Maybe what you should do for time being, if you don't want to
> experiment, is to go back to B-grid with LSR and with no ice-to-
> ocean connection. That configuration worked on the 1/8th and on
> the 1/16th-degree global grids.
>
> D.
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
------------------------------
Message: 5
Date: Thu, 1 Feb 2007 23:06:49 -0500
From: Patrick Heimbach <heimbach at MIT.EDU>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <B2D87B0B-FE95-4C6D-AB0B-7A114C7DAF56 at mit.edu>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Matt,
turning off dynamics for the time being in the Southern Ocean
is a reasonable choice, at least based on 1 deg. tests
(I have figures of daily sea-ice concentration misfits
for various configs, including B-grid LSR, C-grid LSR, C-grid EVP,
and TD only).
Quite possibly this will not be the biggest error related
to sea-ice that you'll be dealing with at the moment.
-p.
On Feb 1, 2007, at 10:12 PM, Matthew Mazloff wrote:
> Hi,
>
> Thanks for the advice. I think I will make a small 1/6 degree
> resolution test box and try running. Until then I want to just run
> without dynamics. I am now using C-grid. For ice-covered areas,
> how is the wind-stress transferred to the ocean if sea-ice dynamics
> are off. Will there be no wind-stress...or will it go right
> through? Do I have any options?
>
> Thanks,
> Matt
>
>
> On Feb 1, 2007, at 9:29 PM, Dimitris Menemenlis wrote:
>
>> Matt, I don't know what to say beyond Jinlun's suggestion. If you
>> tried a 1s time step and if it blew up right away, you would know
>> that something else is wrong. It is a big domain to be trying all
>> these experiments blindly.
>>
>> Maybe what you should do for time being, if you don't want to
>> experiment, is to go back to B-grid with LSR and with no ice-to-
>> ocean connection. That configuration worked on the 1/8th and on
>> the 1/16th-degree global grids.
>>
>> D.
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org
>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
---
Dr Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
MIT | EAPS, 54-1518 | 77 Massachusetts Ave | Cambridge, MA 02139, USA
FON: +1-617-253-5259 | FAX: +1-617-253-4464 | SKYPE: patrick.heimbach
------------------------------
Message: 6
Date: Thu, 01 Feb 2007 21:14:31 -0800
From: Dimitris Menemenlis <menemenlis at sbcglobal.net>
Subject: Re: [MITgcm-support] EVP stability
To: mitgcm-support at mitgcm.org
Message-ID: <45C2C8B7.4080807 at sbcglobal.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> I am now using C-grid. For ice-covered areas, how is the wind-stress
> transferred to the ocean if sea-ice dynamics are off. Will there be no
> wind-stress...or will it go right through? Do I have any options?
Matt, if you turn off dynamics, everything is computed at cell center. There is
no B or C grid. I had a quick look and it seems you will have to use "#undef
SEAICE_CGRID" if you want wind stress to go through the sea ice. Otherwise
there will be wind stress under ice.
D.
------------------------------
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