Ocean Module Reference#

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Ocean Parameters#

Parameter	Default	Description
bc_sa_t	neumann	Top boundary condition of the salinity.
bottom_salinityflux	0.0	Kinematic salinity flux near the ocean bottom.
salinity	.TRUE.	Parameter to switch on/off calculation of the salinity equation.
sa_surface	35.0	Ocean surface salinity.
sa_vertical_gradient	0.0	Salinity gradient(s) of the initial salinity profile.
sa_vertical_gradient_level	0.0	Height level from which on the salinity gradient defined by sa_vertical_gradient is effective.
stokes_waveheight	0.0	Parameter to switch on and set the effects of Langmuir circulation in the ocean mode (height of ocean waves).
stokes_wavelength	0.0	Parameter to switch on and set the effects of Langmuir circulation in the ocean mode (wavelength of ocean waves).
surface_cooling_spinup_time	undefined	Time after which the surface heat flux is switched off.
switch_off_module	.FALSE.	Parameter to switch on/off the module in general.
top_salinityflux	undefined	Kinematic salinity flux at the top boundary, i.e. the sea surface.
wave_breaking	.FALSE.	Switches on turbulence generation by wave breaking.

bc_sa_t#

Fortran Type: C*20

Default: neumann

Top boundary condition of the salinity.

When a constant salinity flux is used at the top boundary (see top_salinityflux), bc_sa_t = 'neumann' must be used, because otherwise the resolved scale may contribute to the top flux so that a constant value of the flux cannot be guaranteed.

Currently 2 choices are available:

• dirichlet

  Salinity at the top (sa(k=nz+1), i.e. sea surface) does not change during the run.

• neumann

  Vertical gradient of the salinity at the top is zero ( sa(k=nz+1) = sa(k=nz) ).

bottom_salinityflux#

Fortran Type: R

Default: 0.0

SI-Unit: psu ms^-1

Kinematic salinity flux near the ocean bottom.

The respective salinity flux value is used as the bottom (horizontally homogeneous) boundary condition for the salinity equation. This additionally requires that a Neumann condition must be used for the salinity, which is currently the only available bottom boundary condition (so it does not need to be set).

See also top_salinityflux.

salinity#

Fortran Type: L

Default: .TRUE.

Parameter to switch on/off calculation of the salinity equation.

You may set salinity = .F. in ocean mixed layer studies (where the turbulent layer is shallow) to save CPU time. In that case, a constant salinity as given by sa_surface is assumed when calculating the equation of state.

In the case of salinity = .F., non-zero values for parameters bottom_salinityflux and top_salinityflux are not allowed.

sa_surface#

Fortran Type: R

Default: 35.0

SI-Unit: psu

Ocean surface salinity.

This parameter is used to set the value of the salinity sa at the sea surface (vertical grid index k=nzt). Starting from this value, the initial vertical salinity profile is constructed from the sea surface down to the bottom of the sea (vertical grid index k=0) by using sa_vertical_gradient and sa_vertical_gradient_level.

sa_vertical_gradient#

Fortran Type: R (10)

Default: 0.0

SI-Unit: psu / 100 m

Salinity gradient(s) of the initial salinity profile.

This salinity gradient holds starting from the height level defined by sa_vertical_gradient_level down to the bottom boundary or down to the next height level defined by sa_vertical_gradient_level. More precisely, for all uv levels, k, where zu(k) < sa_vertical_gradient_level, sa_init(k) is set: sa_init(k) = sa_init(k+1) - dzu(k+1) * sa_vertical_gradient. A total of 10 different gradients for 11 height intervals (10 intervals if sa_vertical_gradient_level(1) = 0.0) can be assigned. The surface salinity at k=nzt is assigned via sa_surface.

Example:

> sa_vertical_gradient = *1.0*, *0.5*,
> sa_vertical_gradient_level = *-500.0*, *-1000.0*,

The example defines the salinity to be constant down to z = -500.0 m with a salinity given by sa_surface. For -500.0 m < z <= -1000.0 m the salinity gradient is 1.0 psu / 100 m and for z < -1000.0 m down to the bottom boundary it is 0.5 psu / 100 m (it is assumed that the assigned height levels correspond with uv levels).

sa_vertical_gradient_level#

Fortran Type: R (10)

Default: 0.0

SI-Unit: m

Height level from which on the salinity gradient defined by sa_vertical_gradient is effective.

The height levels must be assigned in descending order. The default values result in a constant salinity profile regardless of the values of sa_vertical_gradient (unless the bottom boundary of the model is lower than -100000.0 m). For the piecewise construction of salinity profiles see sa_vertical_gradient.

stokes_waveheight#

Fortran Type: R

Default: 0.0

SI-Unit: m

Parameter to switch on and set the effects of Langmuir circulation in the ocean mode (height of ocean waves).

The effects of Langmuir circulation are considered by the Craik-Leibovich vortex force and the Stokes drift velocity, as described in Noh et al. (2004), JPO. In order to switch these effects on, you need to set both parameters, stokes_waveheight and stokes_wavelength to a non-zero positive value. stokes_waveheight sets the height of the ocean surface waves to be used for calculating the vertical profile of the Stokes drift velocity. The direction of the Stokes drift velocity is derived from parameters top_momentumflux_u and top_momentumflux_v, which define the wind stress at the ocean surface.

stokes_wavelength#

Fortran Type: R

Default: 0.0

SI-Unit: m

Parameter to switch on and set the effects of Langmuir circulation in the ocean mode (wavelength of ocean waves).

stokes_wavelength sets the wavelength of the ocean surface waves to be used for calculating the vertical profile of the Stokes drift velocity. See stokes_waveheight for more information about how the Stokes drift is determined.

surface_cooling_spinup_time#

Fortran Type: R

Default: undefined

SI-Unit: s

Time after which the surface heat flux is switched off.

Limits the duration of a surface heat flux forcing. If, for example, a surface cooling is required during an initial spin-up phase for only 15 minutes in order to trigger the development of a Langmuir circulation, the heat flux must be given via top_heatflux and surface_cooling_spinup_time = 900.0 must be set. The default value means that the surface flux is (probably) never switched off.

Attention:
In nested runs surface_cooling_spinup_time should be given the same value in all domains (root domain as well as child domains).

switch_off_module#

Fortran Type: L

Default: .FALSE.

Parameter to switch on/off the module in general.

switch_off_module = .T. can be used to switch off this module without removing (or commenting) the namelist from the namelist file.

top_salinityflux#

Fortran Type: R

Default: undefined

SI-Unit: psu ms^-s

Kinematic salinity flux at the top boundary, i.e. the sea surface.

The respective salinity flux value is used as the top (horizontally homogeneous) boundary condition for the salinity equation. This additionally requires that a Neumann condition for the salinity (see bc_sa_t has been set, because otherwise the resolved scale transport may contribute to the top flux so that a constant salinity flux cannot be guaranteed.

The application of a salinity flux at the model top additionally requires the setting of the initial parameter use_top_fluxes = .T.

See also bottom_salinityflux.

wave_breaking#

Fortran Type: L

Default: .FALSE.

Switches on turbulence generation by wave breaking.

wave_breaking = .T. switches on turbulence generation by wave breaking at the ocean surface. This way, random perturbations are added to the horizontal velocity components at the top model layer (at grid index k = nzt). The parameterization is realized as described in Noh et al. (2004), JPO.

WARNING: The implemented parameterization is designed for a vertical grid spacing of dz = 1.25 m and time steps of about 4 s. It will probably fail for other setups.