[Mitgcm-support] timelabs of velocity

[mitgcm-support at dev.mitgcm.org]

Alistair,

because of the success of your former solution here is another short
question I am struggling with (you see, I am currently in an intensive
programming/debugging phase regarding the floats):

The floats should be integrated by a second Runga-Kutta method. This
requires 2 timesteps of velocity (tau and tau-1) at the time of
integration. Now looking in the code I see that this is not simple.

When the Adam Bashforth timestep is done (timestep.F) there are two
slabs:
	gUNm1   contains the new timestep
	uVel    contains the old timestep
The correction step is done in correction_step.F:
 	uVel now contains the new timestep, the old is overwritten

So, it seems u(tau) and u(tau-1) are never available at the same time.
And to confuse a bit more the correction step is pipeline and calculated
before the AB timestep.

Where would be the best place to put in the float calculation? After
timestep.F? In that case the correction would neglected.

Currently I am using an Euler timestep because of that proble. But
precision might become an issue later and I have to use a higher-order
scheme.

Arne
--

Dr. Arne Biastoch
Scripps Institution of Oceanography        phone: +1-858-822-3787
Physical Oceanography Research Division    fax  : +1-858-534-9820
MS: 0230                                   email: abiastoch at ucsd.edu
8605 La Jolla Shores Dr.            
La Jolla, CA 92093-0230, U.S.A.   http://www.ecco.ucsd.edu/~biastoch