[MITgcm-support] Re: Auto-discard notification

[Martin Losch]

Hi Bin Zhao,

the way the "standard" ocean model is set up, it is volume, not mass 
conserving, and it does not correctly include steric effects. However, 
you can use the pressure coordinate version, which is fully 
non-Boussinesq and thus mass conserving. In this mode all steric 
effects are included (at the cost of some other features that have not 
been implemented yet).

There is even a verification/example-experiment: 
verification/global_ocean_pressure which shows you how to use the 
non-Boussinesq model. I once wrote a small tutorial for this 
experiment, but I cannot find it in the current documentation (does 
anyone have an idea, where it went?).
Equations can be found in Marshall et al. Ocean-Atmosphere modelling 
exploiting the p-z isomorphism and Losch etal. How Sensitive are Coarse 
General Circulation Models to Fundamental Approximations in the 
Equations of Motion? J. Phys. Oceanogr., 34(1): 306-319, 2004.

Things to watch out for in non-Boussinesq mode (pressure coordinates):
Eta is no longer SSH but bottom pressure anomaly
geopotential height g*z at the surface = SSH is stored in PHL.*.data
w is no longer vertical velocity but a pseudo-velocity dp/dt
GM/KPP and most other physical packages are not sorted out properly and 
need some work, but there is no principal problem with those.

Hope that helps,
Martin

On Dec 31, 2004, at 4:08 AM, Ed Hill wrote:

>
>>> Hello,
>>>      I am wondering if the  current model takes account of the SSH
>>> (etaH or etaN) changes due to  warming or cooling of the water
>>> column, i.e., the steric effect. If so, could  you please point to
>>> me the part of the code responsible for  this?
>>>      Thanks for you  help.
>>> Bin Zhao
>
>
> Hi Bin Zhao,
>
> It seems that your email address has changed so I've subscribed you to
> MITgcm-support list with the new address.  If you want to make any
> further changes to your list settings, please see:
>
>   http://dev.mitgcm.org/mailman/listinfo/mitgcm-support
>
>
> In regards to your question, MITgcm supports multiple EoS models (eg.
> linear, JMD95, UNESCO) and the code for them is located primarily in:
>
>   MITgcm/model/src/ini_eos.F
>   MITgcm/model/src/pressure_for_eos.F
>   MITgcm/model/src/find_rho.F
>   MITgcm/model/src/find_alpha.F
>
> As the code shows, changes in temperature and/or salinity can result in
> changes in density which will then have an effect on pressures,
> velocities, etc...
>
> Ed
>
> -- 
> Edward H. Hill III, PhD
> office:  MIT Dept. of EAPS;  Rm 54-1424;  77 Massachusetts Ave.
>              Cambridge, MA 02139-4307
> emails:  eh3 at mit.edu                ed at eh3.com
> URLs:    http://web.mit.edu/eh3/    http://eh3.com/
> phone:   617-253-0098
> fax:     617-253-4464
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://dev.mitgcm.org/mailman/listinfo/mitgcm-support