[MITgcm-support] tidal forcing

[Petter Stenström]

I'm confused.

I add a tidal body force to every grid cell in EXTERNAL_FORCING as
gU=gU+ft*cos(2*pi/T*myCurrentTime). This is the only forcing. The domain
is a simple closed box, cartesian grid, implicit free surface.

In TIMESTEP, uVel then gets updated as uVel=uVel+dt*gU (but stored in gU).

I want the result of this to be that the entire domain is forced with a
tidal body force described as a cumulative cos function.

But, in CORRECTION_STEP, uVel then gets corrected as
uVel=gU-dt*implicsurfpress*phisurfx. The correction term is as large, or
actually slightly larger, as the forcing impulse, so the net result is
that i get a very weak negative forcing when the cos function is positive
and vice versa.

Do I miss something obvious?

Petter