[MITgcm-support] Updated Question: ISOMIP Boundary Condition Setup

[Jean-Michel Campin]

Hi Yilang,

Regarding your previous email, there is also a secondary set-up in verification/isomip
that has some open water (and is further away from the ISOMIP paper) in:
 verification/isomip/input.icefront/

And see some comments below.

On Mon, Jul 30, 2018 at 01:41:27AM -0400, Yilang Xu wrote:
> Hi, 
> 
>  
> 
> Let me update my previous question to make it more specific. For ISOMIP exp1, based on the model setup, outputs and Losch (2008) paper, I assume that the original setup of the boundary conditions in the verification/isomip/input is: (Correct me if anything is wrong)
> 
>  
> 
> Top (if there is open water area): Free surface, set up by rigidLid=.FALSE., implicitFreeSurface=.TRUE., in data file
The free-surface applies everywhere since the ice-shelf is floating.

> Bottom: Free-slip, set up by no_slip_bottom=.FALSE., in data file
> 
> The lateral B.C.s: Closed walls and free-slip, set up by no_slip_sides=.FALSE., in data file
> 
>  
> 
> However, I notice that in gendata.m file, the south and west lateral boundaries have additional treatment as follows: 
> 
> bathy = ones(nx,ny)*H; 
> 
> bathy(1,:) = 0; 
> 
> bathy(:,1) = 0;
> 
> Hence, the south and west boundaries are marked as land or solid boundaries by setting bathymetry=0, while the north and east do not have this treatment. 

This is the usual way a closed domain (on both end) is specified. You can check the documentation
(old) manual, section 3, for instance, 3.9.3 and corresponding gendata.m in:
 MITgcm/verification/tutorial_barotropic_gyre/input
If you do not specify any wall (either on East side or on West side) then the domain is assumed to be
periodic in X direction, and similarly for Y direction without wall in N or S side.

> Initially, I thought this was unnecessary because the lateral boundaries are already closed and free-slip, but if I remove this treatment, the code blows up. 
 
I am not surprised since, in this case, you are trying a periodic domain in latitudinal direction 
and this is difficult to achive with usingSphericalPolarGrid=T.

Cheers,
Jean-Michel

> Therefore, I am wondering why we need this special treatment for the south and west B.C.s, which turns out to be very important. Meanwhile, appreciate it if anyone could help me to check my statement of B.C. setup. 
> 
>  
> 
> Thanks,
> 
> Yilang
> 
>  
> 
> From: MITgcm-support <mitgcm-support-bounces at mitgcm.org> on behalf of Yilang Xu <yxu at whoi.edu>
> Reply-To: <mitgcm-support at mitgcm.org>
> Date: Thursday, July 26, 2018 at 11:40
> To: "mitgcm-support at mitgcm.org" <mitgcm-support at mitgcm.org>
> Subject: [MITgcm-support] ISOMIP default open water boundary condition
> 
>  
> 
> Hi, 
> 
>  
> 
> I try to add an open water area near the ice shelf front in SHELFICE package - ISOMIP exp1. I am wondering, if I just extend the domain further north to create the open water, without using OBCS package, what the default boundary condition would be for this open water area. 
> 
> Moreover, for ISOMIP example in verification directory, what are the boundary conditions in the eastern and northern sides? They are not specified in gendata.m file. 
> 
>  
> 
> Thanks,
> 
> Yilang
> 
> _______________________________________________ MITgcm-support mailing list MITgcm-support at mitgcm.org http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support 
> 

> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support