MPAS-Ocean Nonhydrostatic

A nonhydrostatic capability has been added to MPAS-Ocean. The hydrostatic formulation has been changed including:

• A new equation for the vertical momentum.
• A new nonhydrostatic pressure contribution (in addition to the standard hydrostatic one).

At every time-step, a three-dimensional elliptic equation that governs the nonhydrostatic pressure is solved. The external PETSc library is used for the solution of this elliptic equation. A new namelist section named nonhydrostatic_pressure is present, where the flag
config_enable_nonhydrostatic_mode = .true.
turns on (and off) the nonhydrostatic model.