Pressure in the NonhydrostaticModel

[tomdjohnson]

I am trying to form a simulation in geostrophic balance, which involves setting the pressure gradient to balance the Coriolis force, but I cannot find an example of setting or getting the pressure field. Can I get any help with this, please?

[glwagner]

Pressure is a diagnostic quantity which is computed prior to every time-step from the prognostic fields, so set! on pressure directly doesn't do anything.

You can find the pressure fields in model.pressures for the NonhydrostaticModel:

Oceananigans.jl/src/Models/NonhydrostaticModels/nonhydrostatic_model.jl

Line 49 in 3fe5e9e

pressures :: Φ # Container for hydrostatic and nonhydrostatic pressure

this is plural, because there is an optional decomposition of the pressure into a hydrostatic anomaly (computed from the buoyancy field) and a nonhydrostatic residual. This decomposition can be controlled by the user.

For HydrostaticFreeSurfaceModel there is a single pressure, model.pressure:

Oceananigans.jl/src/Models/HydrostaticFreeSurfaceModels/hydrostatic_free_surface_model.jl

Line 44 in 3fe5e9e

pressure :: Φ # Container for hydrostatic pressure

I believe that the problem of computing an exactly discretely balance velocity and buoyancy field requires solving an elliptic equation for the geostrophic streamfunction. Is this what you would like to do? Putting this together requires a bit of code and using the CG solver in Solvers, but is certainly possible.