15.15. Baroclinic Jet

Effective resolution is limited by the numerical dissipation range, which is a function of the model numerical filters (assuming that dispersive numerical modes are efficiently removed). Soufflet et al. [2016] present a Baroclinic jet test case set in a zonally reentrant channel that provides a controllable test of a model capacity at resolving submesoscale dynamics.

A semi-idealized configuration in a periodic channel is set up to generate two dominant mechanisms of upper ocean turbulence: (i) surface density stirring by mesoscale eddies and (ii) fine scale instabilities directly energizing the submesoscale range. The setup consists of a flat reentrant channel of 500 km by 2000 km by 4000 m, centered around 30 deg of latitude on a \(\beta\)-plane (the Coriolis frequency is \(1.10^{-4}s^{-1}\) at the center, \(\beta= 1.6 10^{-11} m^{-1} s^{-1}\)). Eastern/western boundary conditions are periodic while northern/southern conditions are closed. The initial density field is constructed with interior and surface meridional density gradients and associated geostrophic currents that are linearly unstable to both interior baroclinic and Charney instability modes. A linear stability analysis provides the exponential growth rate of unstable modes as a function of wavenumber. The two most unstable modes are clearly distinct in length scales on either side of the Rossby deformation radius ( around 30 km in the center +/- 5 km from south to north). The interior geostrophic instability thus injects energy at mesoscale and Charney instability at submesoscale if resolution allows (2 km). The default resolution is 20 km (40 vertical levels) where only mesoscale instabilities are at work.

# define JET

CPP options:

# define ANA_JET
# undef  MPI
# undef  NBQ
# define SOLVE3D
# define UV_COR
# define UV_ADV
# define UV_VIS2
# ifdef ANA_JET
#  define ANA_GRID
#  define ANA_INITIAL
# endif
# define ANA_STFLUX
# define ANA_SMFLUX
# define ANA_BSFLUX
# define ANA_BTFLUX
# define ANA_VMIX
# define EW_PERIODIC
# define CLIMATOLOGY
# ifdef CLIMATOLOGY
#  define ZCLIMATOLOGY
#  define M2CLIMATOLOGY
#  define M3CLIMATOLOGY
#  define TCLIMATOLOGY
#  define ZNUDGING
#  define M2NUDGING
#  define M3NUDGING
#  define TNUDGING
#  define ROBUST_DIAG
#  define ZONAL_NUDGING
#  ifdef ANA_JET
#   define ANA_SSH
#   define ANA_M2CLIMA
#   define ANA_M3CLIMA
#   define ANA_TCLIMA
#  endif
# endif
# define LMD_MIXING
# ifdef  LMD_MIXING
#  undef  ANA_VMIX
#  define ANA_SRFLUX
#  undef  LMD_KPP
#  define LMD_RIMIX
#  define LMD_CONVEC
# endif
# define NO_FRCFILE

Settings :

Results :

JET results : initial state

JET results : results after 180 days

JET results : vorticity evolutione