[MITgcm-support] Questions about EXF and OBCS

[Martin Losch]

Dear Han

this can have many reasons. hFlux is computed from different heat flux components. You only prescribe swdown, lwdown directly, the remaining components are computed from atemp, aqh, u/vwind (which you can check apriori) and ocean surface variables like theta, salt, etc. If your model develops weird surface values for, e.g. theta, then you can also get weird. (but 1600W/m^2 is not yet outrageous). Where in your domain does this happen (bi,bj,i,j, values help with this)? 
You can turn off the check (useExfCheckRange=.FALSE. in data.exf) and see what happens, or inspect your surface fields closely (maybe not in time averaged fields, but snapshots of less than 3h intervals). It’s very likely that with OBSC, there are issues near the boundaries and that the model develops some strange fields because of too strong convergence/divergence, when the boundary conditions are not carefully chosen. 

Martin

> On 11. Jun 2025, at 16:54, han <hylhwyjy at 163.com> wrote:
> 
> Dear MITgcm community,
> I am running a case with open boundaries all around, with a model resolution of 0.03 and output every 3 hours. When I don't add boundary conditions (OBCS),  the program can run successfully. However, once the boundary conditions are added and all other data  remains unchanged, the program displays the error  'STOP ABNORMAL END: S/R EXF_CHECK_RANGE ' after running for a period of time. Nevertheless, whether boundary conditions(OBCS) are added or not, the model will appear obvious deviations from the third hour (the data differed significantly from the normal values). I'm not sure what the problem is, or what methods can I try to solve this problem?
> My EXF uses swdown, lwdown, precip, atemp, aqh, uwnd and vwnd data, and ensures that each value is within the required range.
> After adding the boundary, EXF_CHECK_RANGE is displayed, and the following content will be shown in STDOUT
> 
> cg2d: Sum(rhs),rhsMax = 2.42073525314462E+06 1.99340964002214E+01
> EXF WARNING: hflux out of range for bi,bj,i,j,it= 1 1206 8 40334 0.160016382290418D+04
> EXF WARNING: If you think these values are OK
> EXF WARNING: then set useExfCheckRange=.FALSE.
> 
> I would appreciate any suggestions.
> 
> Best regards,
> Han
> 
> 
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