[MITgcm-support] Open boundary conditions

Dustin Carroll dcarroll at uoregon.edu
Thu Oct 23 11:24:43 EDT 2014

Hi Xiangming,

OBCSbalance = .TRUE., will balance at each time step. If your OB forcing period is not equal to your time step, the OB will be linearly interpolated at each time step — (i.e., the balance time scale is determined by your deltaT).

With OBCSbalance off, the model eta is just responding to what you are prescribing at the OB — so double check that your net transport is 0 at the boundary (u+v).

As Martin recommended, there is lots of useful information in the listserv archives on this topic. Also look at documentation section 6.3.1


On Oct 23, 2014, at 9:40 AM, Xiangming Zeng <xzeng2 at ncsu.edu> wrote:

> Hi Dustin and Martin, 
> Thanks a lot for your reply. The OBC I provided is the HYCOM velocity (u and v) and TS. Actually, for my case, there's only one eastern open boundary. Following previous discussion in the mailing list, I did the OBCS balance during the preprocessing with one day time scale ( because the OB data is provided every day). 
> However, I still have several questions:
> 1) During the OBCS preprocessing, I only balanced the U velocity along eastern boundary. I'm not sure whether it's right or not. Because the change of U will affect the velocity direction along the open boundary ( remember V is not changed).
> 2) For the OBCSbalance option, does it balance the in/out flow every time step? Furthermore, what's the influence of different balance time scale (e.g., every time step/day/month)? Is the balance time scale determined by the time interval of OB data provided? 
> Thanks much for all your help.
> Best,
> Xiangming 
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