[MITgcm-devel] code changes

[Martin Losch]

Hi Matt,
thanks for the clarification, I was not aware of that at all.

This ordering makes some sense, as the normal velocity is usually more important than the tangential velocity. But it is a little confusing, especially, since there is no obvious documentation about that (not even in the code).

Martin


On Mar 10, 2011, at 8:12 PM, Matthew Mazloff wrote:

> Hello,
> 
> The ordering for obcs controls is T / S / normal vel /  tangential vel.  This is consistent throughout the code
> 
> -Matt
> 
> 
> On Mar 10, 2011, at 9:22 AM, Holly Dail wrote:
> 
>>>> Hate to open other cans of worms, but there is some inconsistency in the code re. the ordering of obcs control fields.  I believe the code pieces I'm using assume the 3rd field is vvel and 4th field is uvel (i.e. they are packed T/S/V/U -- see for example ctrl_getobcss.F where OBSu is modified when iobcs is 4), while code like cost_obcsvol.F assumes they are packed T/S/U/V (which is more logical, but this code is never called from any other S/R).  I can't figure out right now which order they are packed into the control files.  I'm mostly concerned as to whether its all consistent, rather than whether its illogical.
>>> I can only recommend to avoid code within #ifdef ALLOW_CTRL_OBCS_BALANCE. The code does not look right to me. I think Jake tried to balance both normal and tangential xx_velocities (why?) and might have mixed up things? Plus, there are definitely hfac's missing in this computation, so leave it alone. The ordering is T/S/U/V for the obcs and this is also true for the ctrl-fields.
>>> For balanced flow even with optimized boundary flow you can (probably) use the "forward" flags OBCSuseBalance with all the new features checked in by Jean-Michel. I am currently using an older hacked version which does effectively what Jean-Michel implemented more generally, and this gives fine results (in terms of balancing).
>> 
>> I'm attaching the relevant bits from ctrl_getobcss.F in which I believe the ordering is T/S/V/U:
>> 
>>           else if (iobcs .EQ. 4) then
>>            OBSu(i,k,bi,bj) = OBSu (i,k,bi,bj)
>>    &            + obcssfac            *xx_obcss0(i,k,bi,bj,iobcs)
>>    &            + (1. _d 0 - obcssfac)*xx_obcss1(i,k,bi,bj,iobcs)
>>            OBSu(i,k,bi,bj) = OBSu(i,k,bi,bj)
>>    &            *maskW(i,j,k,bi,bj)
>>           else if (iobcs .EQ. 3) then
>>            OBSv(i,k,bi,bj) = OBSv (i,k,bi,bj)
>>    &            + obcssfac            *xx_obcss0(i,k,bi,bj,iobcs)
>>    &            + (1. _d 0 - obcssfac)*xx_obcss1(i,k,bi,bj,iobcs)
>>            OBSv(i,k,bi,bj) = OBSv(i,k,bi,bj)
>>    &            *maskS(i,j+jp1,k,bi,bj)
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> 
> 
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Martin Losch
Martin.Losch at awi.de