[MITgcm-support] Question about pressure

[mdunphy at uwaterloo.ca]

Hi all,

I'm working on an energy budget for MITgcm and am finding a somewhat  
large residual in kinetic energy. Time stepping is Adams-Bashforth-3,  
surface is rigid lid, EOS is linear. The kinetic energy residual  
converges *linearly* with time-step. I was expecting it to converge  
better than first order due to use of AB3.

In looking through the manual, the section on pressure method for  
rigid-lid mentions:

> The particular location in time of the pressure field is somewhat  
> ambiguous; in Fig. 2.1 we depicted as co-located with the future  
> flow field (time level n + 1) but it could equally have been drawn  
> as staggered in time with the flow.

If pressure is offset from velocity in time, that could explain the  
linear convergence of the kinetic energy (due to the u*p' energy flux  
term).

I reproduced the calls to CALC_PHI_HYD at the end of the time step,  
but it produced the same values of totPhihyd as were computed earlier  
in the time step in dynamics.F.

Is there a way to get pressure that does not have an ambiguous time?


Cheers,
Michael