[MITgcm-support] rbcs advice

[Jody Klymak]

One other quick question that I know has come up before but I can't seem to find...

I have snapshots at t=0,3600,7200, and I want to use them for my obcs.  However, I seem to remember that externalForcingPeriod=3600 assumes the first file entry is at t=1800, the second at 5400s etc.  Is there an offset to change this so that the first is t=0, etc, or do I have to hack get_periodic_interval.F?  

Thanks,   Jody


On Mar 4, 2014, at  9:18 AM, Jody Klymak <jklymak at uvic.ca> wrote:

> Hi Dimitris,
> 
> I wrote you offline as well, but...
> 
> On Mar 4, 2014, at  9:06 AM, Dimitris Menemenlis <dmenemenlis at gmail.com> wrote:
> 
>> Hi Jody, I think yes.  What grid spacing are you running your regional domain?
>> And what resolution (space and time) is your open boundary conditions?
> 
> Right now I have hourly (well 3720 s to be an even divisor of an M2 tidal cycle) output on a 5- to 1-km grid, with 1 km near my region of interest, and 5 km at the boundaries.  The forcing of this model was an analytical source function (a couple of internal tide line-sources outside the domain), and the model was spun up for 12 tidal cycles allowing reflections from a rough continental slope to set up. Probably accurate out to mode 10 or so.  
> 
> I am trying to telescope this down to about 100x200 m in a 50x100 km region to look at the non-linear internal waves on a continental slope.  I nest this inside a 400x300 km region using telescoping resolution, and will initialize and force with the larger 1-km grid. 
> 
> All the telescoping is to help make the BCs not too important, but it would be nice to make them as close as possible to reduce reflections. 
> 
> Thanks!   Jody
> 
>> 
>> Michael Schodlok has a lot of experience going from
>> CS510 (18 km) to 1 km domains, then adding tides,
>> and possibly obcs sponge to get rid of some edge artifacts.
>> 
>> But with sufficiently high-resolution (in time) obcs,
>> I am guessing that you will not need sponging at all.
>> At least that's the theory.
>> Chris Hill was experimenting with "replaying" bits
>> of the 1/48th using obcs.  I don't know how far he got.
>> 
>> Let me know if you want to access the 1/48th output
>> and we can figure out best way to proceed.
>> 
>> Cheers, Dimitris
>> 
>> On Mar 4, 2014, at 8:50 AM, Jody Klymak <jklymak at uvic.ca> wrote:
>> 
>>> Do you think its true that I could just force w/ obcs and do away w/ the sponge? I've used sponges for so long I hadn't thought of giving this a try, but maybe it is all I need to do, and I can ditch rbcs.  Certainly my forcing should have all the modes that could conceivably reach the boundaries by the time my integration is done.  
>>> 
>>> Second, 1/48th degree global with tides!  That would be very interesting!
>> 
>> 
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> --
> Jody Klymak    
> http://web.uvic.ca/~jklymak/