[Mitgcm-support] ISOTROPIC_COS_SCALING

[mitgcm-support at dev.mitgcm.org]

Alistair, are you aware of possible problem with the ISOTROPIC_COS_SCALING
option in GAD_OPTIONS.h?

The reason I ask is that in configuring the 1/4-deg model, Benny finds that he
can use 1000-s time steps with biharmonic friction in the non-isotropic
configuration but is unable to use biharmonic friction in the isotropic
configuration.  Even with 100-s time step, the model crashes within 20 time
steps.  This forces him to use Laplacian friction, which makes the model more
viscous, and to reduce the time step from 1000 to 600 s.

>From his 1/12-deg tests, Armin suggests to try "not using"

 tempAdvScheme=4
 saltAdvScheme=4

Could there be a possible conflict between ISOTROPIC_COS_SCALING and 4-th
order advection?  Any other clues or sugestions for reducing viscosity and
increasing time step in the 1/4-deg configuration?

Dimitris

-- 
Dimitris Menemenlis                      menemenlis at jpl.nasa.gov
Jet Propulsion Lab, MS 300-323           tel: 818-354-1656
4800 Oak Grove Dr, Pasadena CA 91109     fax: 818-393-6720