[MITgcm-support] obcs adjoint issue (I need dynamics.F help)

[Matthew Mazloff]

Hello,

I have been using the open boundary controls.  The sensitivities for  
the velocity normal to the boundary appear unphysical.  (I am using a  
northern boundary so for my case V is the normal vel.)  I have  
tracked down what is causing this.  It is that on the open boundary  
the adjoint variable of gV has an odd structure.  And because  
dynamics.F calls OBCS_APPLY_UV twice, this odd structure gets added  
to the sensitivities twice.  Calling  OBCS_APPLY_UV( bi, bj, k, gU,  
gV, myThid ) is rather benign in the forward integration, U and V on  
the open boundary get written over anyway.  In the adjoint  
integration, however, every call matters.  Could someone more expert  
in the dynamics.F routine please check if all these calls are  
necessary.  And I'd really appreciate it if they could also fill me  
in as to why they are there.

Thanks,
Matt

ps> I'm using vectorInvariantMomentum and implicitViscosity