[MITgcm-support] eta at OBCS

[Stefano Querin]

Hi Ming,
just some hints (I'm a bit busy in these days, sorry...).
There are many mails about eta and OBCs: try to find them on the mitgcm 
website, you will find lots of informations.
Anyway, if you need to impose eta on the OB (i.e. external tidal 
forcing...), I suggest you to convert the sea surface elevation (eta) into 
barotropic velocity (Vbaro) "offline":

Vbaro=c*eta/H

c=(gH)**1/2

g: gravity acc.;
H: water column heigth;
c: celerity of small (compared to the water column heigth: eta<<H) amplitude 
perturbations.

It is also possible to impose u, v, w, T, S and eta as well: you have to 
customize some routines (I modified obcs_prescribe_read.F , exf_set_obcs.F , 
obcs_readparms.F , OBCS.h , OBCS_OPTIONS.h  in such a way to be able to read 
OBeta values from files). Remember to set  #define NONLIN_FRSURF in 
CPP_OPTIONS.h and nonLinFreeSurf~=0 in data (if I remeber correctly...): in 
this case you must run only in hydrostatic mode.

If you need a radiation condition on the OB: Orlanski OBC does not control 
the inflow/outflow in the domain so you could obtain a very anomalous 
increase/decrease in the sea surface level (for example, try to run the 
plume on slope verification experiment for a longer period)!

If there is something wrong, please someone correct me!
Good luck!

Stefano


----- Original Message ----- 
From: "Ming Guo" <gming at karluk.physics.mun.ca>
To: <mitgcm-support at mitgcm.org>
Sent: Wednesday, October 19, 2005 4:09 PM
Subject: Re: [MITgcm-support] eta at OBCS


> Is obcs_apply_eta.f the file should be included?
> But I am not sure how to do it.
>
>
> On Wed, 19 Oct 2005, Ming Guo wrote:
>
>> Hi,
>> anyone can give me some hints or examples of dealing with eta on open 
>> boundary?
>>
>> It seems that obcs only calculates u,v,w,s and t.
>>
>> thanks,
>>
>> Ming
>>
>> _______________________________________________
>> 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
>