[MITgcm-devel] obcs_seaice_sponge.F

[Menemenlis, Dimitris (3248)]

Jean-Michel, I just checked in obcs_seaice_sponge.F and verification experiment.
I did not on turn on sponge for oceanic fields, as you recommend below.

Regarding obcs_sponge.F
I just realize that Ian and Michael also run into problem described below and fixed in a local copy:
http://ecco2.jpl.nasa.gov/data3/MPS_output/pub/patrick/code/obcs_sponge.F

Would it be OK if I check in their fix, with ALLOW_OBCS_LINEAR undefed by default,
so as not to affect existing set-ups, and with proper comments and explanation in OBCS_OPTIONS.h
That way the next person that may look at this routine does not have to find the bug anew?

Let me know.

Dimitris Menemenlis

On Sep 20, 2012, at 11:46 AM, Jean-Michel Campin wrote:

> Hi Dimitris,
> 
> Yes, this is part of the long list of issues with OBCS SPONGE.
> And by the way, I think it would be better not to turn on the sponge 
> for oceanic fields when you add this to exp seice_obcs, because regarding
> velocity (as you mentionned) there are other issues.
> 
> Jean-Michel
> 
> On Thu, Sep 20, 2012 at 05:45:58PM +0000, Menemenlis, Dimitris (3248) wrote:
>> Jean-Michel and Patrick, I know that it is no longer actively supported but, for the record, there
>> seems to be a problem with obcs_sponge.F, and it dates back to very first check in 10+ years ago.
>> 
>> According to comments, the relaxation time scale is supposed to be linear
>> and controlled by U/Vrelaxobcsinner/bound:
>> 
>> C U/Vrelaxobcsinner/bound :: relaxation time scale (in seconds) on the boundary
>> C                            (bound) and at the innermost grid point of the sponge
>> C                            layer (inner); relaxation time scales in-between
>> C                            are linearly interpolated from these values
>> 
>> But as coded, the relaxation is quadratic because there is an additional attenuation term due
>> to linearly decreasing u/v/t/srelax as it goes away from the boundary.
>> 
>> Additionally, as coded, relaxation will be zero if spongeThickness = 1.
>> 
>> I will fix these two problems in obcs_seaice_sponge.F before checking in,
>> 
>> Let me know if you want me to do anything about these two problem in obcs_sponge.F
>> 
>> Cheers
>> 
>> Dimitris Menemenlis