[MITgcm-support] Thermal wind in ocean cause too large velocity?
Chun-Yan Zhou
c.zhou at dundee.ac.uk
Thu May 24 05:07:55 EDT 2012
Hi Jody,
Thanks for your reply.
you mentioned that If I want the model to be in geostrophic balance at startup, I need to specify the velocities in the initial conditions as well. But I have no idea how to specify the initial velocities. I just know the initial temperature and salinity conditions. Do you have any reference to calculte the initial velocities?
Thank you very much!
Chunyan Zhou
Division of Civil Engineering
School of Engineering, Physics and Mathematics
College of Art, Science and Engineering
Fulton Building,G19
University of Dundee
Dundee, UK DD1 4HN
Tel. 01382 385431
________________________________________
----------------------------------------------------------------------
Message: 1
Date: Mon, 21 May 2012 10:28:42 -0700
From: Jody Klymak <jklymak at uvic.ca>
To: mitgcm-support at mitgcm.org
Subject: Re: [MITgcm-support] Thermal wind in ocean cause too large
velocity?
Message-ID: <63EBD0BA-0022-4E11-96BF-1AE83E7A2923 at uvic.ca>
Content-Type: text/plain; charset=us-ascii
If you start your model with zero velocity and a large horizontal temperature gradient, it will undergo a Rossby adjustment first which can have large wave velocities associated with it, though 4 m/s seems large. The Coriolis force takes at least an inertial period to become important.
If you want your model to be in geostrophic balance at startup, you need to specify the velocities in the initial conditions as well.
Cheers, Jody
On May 21, 2012, at 4:38 AM, Chun-Yan Zhou wrote:
> Based on
> The temperature difference in horizontal direction can cause large velocity because of thermal wind.
> And I did a test where the initial temperature field changed form 20-13 degree along the X direction, no other forces are applied.
> Large velocity is expected, but the maximum velocity is 4m/s, and the minimum is -4m/s, most of the velocity is around 1.5m/s. Is the velocity should be so large?
> Any suggestion is appreciated.
> chunyan
>
> # ====================
> # | Model parameters |
> # ====================
> #
> # Continuous equation parameters
> &PARM01
> tRef=20*20.,
> sRef=20*35.,
> viscAh=4.E-2,
> viscAz=4.E-2,
> no_slip_sides=.FALSE.,
> no_slip_bottom=.FALSE.,
> diffKhT=4.E-2,
> diffKzT=4.E-2,
> f0=0.E-4,
> beta=0.E-11,
> tAlpha=2.0E-4,
> sBeta =0.,
> tempAdvScheme=77,
> gravity=10.,
> rhoConst=1000.,
> rhoNil=1000.,
> heatCapacity_Cp=4000.,
> #rigidLid=.TRUE.,
> implicitFreeSurface=.TRUE.,
> #exactConserv=.TRUE.,
> eosType='LINEAR',
> nonHydrostatic=.TRUE.,
> saltStepping=.FALSE.,
> staggerTimeStep=.TRUE.,
> &
>
> # Elliptic solver parameters
> &PARM02
> cg2dMaxIters=1000,
> cg2dTargetResidual=1.E-9,
> cg3dMaxIters=1000,
> cg3dTargetResidual=1.E-9,
> &
>
> # Time stepping parameters
> &PARM03
> nIter0=0,
> #endTime=43200.,
> nTimeSteps=21600,
> deltaT=10.,
> abEps=0.1,
> pChkptFreq=43200.,
> chkptFreq=7200.,
> dumpFreq=1800.,
> monitorFreq=600.,
> monitorSelect=1,
> monitorFreq=1.,
> &
>
> # Gridding parameters
> &PARM04
> usingCartesianGrid=.TRUE.,
> dXspacing=100.,
> dYspacing=100.,
> delZ=50*20.,
> &
>
> # Input datasets
> &PARM05
> hydrogThetaFile='T.bin',
> &
> %%%%%%%%%%%gendata.m
> var=zeros(100,100,50);
> for i=1:100
> var(i,:,:)=20-0.07*(i-1);
> end
> fid=fopen('T.bin','w','b'); fwrite(fid,var,'real*4'); fclose(fid);
>
>
>
> Dear all,
>
>
>
>
> The University of Dundee is a registered Scottish Charity, No: SC015096
>
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
--
Jody Klymak
http://web.uvic.ca/~jklymak/
------------------------------
Message: 2
Date: Tue, 22 May 2012 09:23:37 +0200
From: Martin Losch <Martin.Losch at awi.de>
To: mitgcm-support at mitgcm.org
Subject: Re: [MITgcm-support] Thermal wind in ocean cause too large
velocity?
Message-ID: <1153B129-BB82-4EE3-9F5A-918B4A97B0B6 at awi.de>
Content-Type: text/plain; CHARSET=US-ASCII
On top of Jody's very valid statement about adjustment processes, for the pure geostrophic balance I extract this from your information:
dx=100 (m), Lx=100*100=10km, dz=20m, Lz=1000m
rho(S=0,T=20,p=0)-rho(S=0,T=13,p=0) = -1.17 kg/m^3
thermal wind gives
dv/dz = - g/f/rho0 drho/dx = 9.81/1.e-4/1000 * 1.17 /10e3 m/s = 0.0115 m/s*(1/m)
integrating only over the first 5layers already gives dv/dz*100m = 1.15 m/s and with the full depth you'd get 11.5m/s, so I am not suprised by your 1.5m/s
Martin
On May 21, 2012, at 7:28 PM, Jody Klymak wrote:
> If you start your model with zero velocity and a large horizontal temperature gradient, it will undergo a Rossby adjustment first which can have large wave velocities associated with it, though 4 m/s seems large. The Coriolis force takes at least an inertial period to become important.
>
> If you want your model to be in geostrophic balance at startup, you need to specify the velocities in the initial conditions as well.
>
> Cheers, Jody
>
>
> On May 21, 2012, at 4:38 AM, Chun-Yan Zhou wrote:
>
>> Based on
>> The temperature difference in horizontal direction can cause large velocity because of thermal wind.
>> And I did a test where the initial temperature field changed form 20-13 degree along the X direction, no other forces are applied.
>> Large velocity is expected, but the maximum velocity is 4m/s, and the minimum is -4m/s, most of the velocity is around 1.5m/s. Is the velocity should be so large?
>> Any suggestion is appreciated.
>> chunyan
>>
>> # ====================
>> # | Model parameters |
>> # ====================
>> #
>> # Continuous equation parameters
>> &PARM01
>> tRef=20*20.,
>> sRef=20*35.,
>> viscAh=4.E-2,
>> viscAz=4.E-2,
>> no_slip_sides=.FALSE.,
>> no_slip_bottom=.FALSE.,
>> diffKhT=4.E-2,
>> diffKzT=4.E-2,
>> f0=0.E-4,
>> beta=0.E-11,
>> tAlpha=2.0E-4,
>> sBeta =0.,
>> tempAdvScheme=77,
>> gravity=10.,
>> rhoConst=1000.,
>> rhoNil=1000.,
>> heatCapacity_Cp=4000.,
>> #rigidLid=.TRUE.,
>> implicitFreeSurface=.TRUE.,
>> #exactConserv=.TRUE.,
>> eosType='LINEAR',
>> nonHydrostatic=.TRUE.,
>> saltStepping=.FALSE.,
>> staggerTimeStep=.TRUE.,
>> &
>>
>> # Elliptic solver parameters
>> &PARM02
>> cg2dMaxIters=1000,
>> cg2dTargetResidual=1.E-9,
>> cg3dMaxIters=1000,
>> cg3dTargetResidual=1.E-9,
>> &
>>
>> # Time stepping parameters
>> &PARM03
>> nIter0=0,
>> #endTime=43200.,
>> nTimeSteps=21600,
>> deltaT=10.,
>> abEps=0.1,
>> pChkptFreq=43200.,
>> chkptFreq=7200.,
>> dumpFreq=1800.,
>> monitorFreq=600.,
>> monitorSelect=1,
>> monitorFreq=1.,
>> &
>>
>> # Gridding parameters
>> &PARM04
>> usingCartesianGrid=.TRUE.,
>> dXspacing=100.,
>> dYspacing=100.,
>> delZ=50*20.,
>> &
>>
>> # Input datasets
>> &PARM05
>> hydrogThetaFile='T.bin',
>> &
>> %%%%%%%%%%%gendata.m
>> var=zeros(100,100,50);
>> for i=1:100
>> var(i,:,:)=20-0.07*(i-1);
>> end
>> fid=fopen('T.bin','w','b'); fwrite(fid,var,'real*4'); fclose(fid);
>>
>>
>>
>> Dear all,
>>
>>
>>
>>
>> The University of Dundee is a registered Scottish Charity, No: SC015096
>>
>>
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org
>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>
> --
> Jody Klymak
> http://web.uvic.ca/~jklymak/
>
>
>
>
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
------------------------------
Message: 3
Date: Tue, 22 May 2012 15:47:58 +0200
From: Maura BRUNETTI <Maura.Brunetti at unige.ch>
To: mitgcm-support at mitgcm.org
Subject: [MITgcm-support] speedup for cs64 on a linux cluster
Message-ID: <76a0ed8329b9b7.4fbbb52e at unige.ch>
Content-Type: text/plain; charset="iso-8859-1"
Dear MITgcm users,
I am studying scaling properties of ocean-only configurations on a linux cluster.
The results shown in the attached figure are obtained with a cubed sphere configuration with 64x64 face resolution and 15 vertical levels (points in the figure correspond to: 6 tiles 64x64 on 1 proc, 1 tile 64x64 on 6 procs, 1 tile 32x64 on 12 procs, 1 tile 32x32 on 24 procs and 1 tile 16x32 on 48 procs). Only packages GMredi and tave are activated at run time.
The scaling is not very good, starting already at 12 procs (see blue line). I have not found in the literature other scaling analysis, could you please suggest where I can find them? From my analysis, I have seen that it is not worth doing runs with tile dimension smaller than 32 grid points. Is it correct?
Thanks,
Maura ? ? ??
--
Dr. Maura Brunetti
Institute for Environmental Sciences (ISE)
University of Geneva -- Switzerland
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20120522/124c3a12/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: speedup.eps
Type: application/postscript
Size: 10762 bytes
Desc: not available
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20120522/124c3a12/attachment.eps>
------------------------------
_______________________________________________
MITgcm-support mailing list
MITgcm-support at mitgcm.org
http://mitgcm.org/mailman/listinfo/mitgcm-support
End of MITgcm-support Digest, Vol 107, Issue 17
***********************************************
The University of Dundee is a registered Scottish Charity, No: SC015096
More information about the MITgcm-support
mailing list