[MITgcm-support] nonhydrostatic and kpp

[Sherry]

Hi all,

I have a 2-D nonhydrostatic configuration of an internal wave beam forced
through specifying u, v, w, and temperature at the western boundary. At the
moment I am trying to reproduce an experiment that was done in 2009
(Grisouard and Staquet, 2010), but for some reason I am getting
instabilities after about 10 wave cycles, even though I am using the same
input parameters. Could there be some changes in the model since 2009 that
would affect default values? Any advice about how to track these down?

To control the instabilities I am trying higher diffusion values, as well
as turning on KPP. However, it seems there is some internal inconsistency
with the configuration being nonhydrostatic, and I get the following
warnings (from config_check.F):

WARNING  CONFIG_CHECK: Implicit viscosity applies to provisional u,vVel
WARNING  => not consistent withfinal vertical shear (after appling 3-D
solver solution
WARNING  CONFIG_CHECK: Implicit viscosity not implemented in CALC_GW
WARNING  CONFIG_CHECK: Explicit viscosity might become unstable if too large

Should I be concerned about these warnings? Is there any way around them
since nonhydrostatic requires 3-D solver and KPP requires implicit
viscosity?

Thanks for reading!

Sherry Chou
University of Hawaii
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