PUBLIC INTERFACE ~ PUBLIC ROUTINES ~ NAMELIST

Module ocean_bihcst_friction_mod

Contact:  Stephen M. Griffies
Reviewers: 
Change History: WebCVS Log

OVERVIEW

Thickness weighted and density weighted time tendency for velocity from horizontal biharmonic friction

This module computes the thickness and density weighted time tendency for horizontal velocity arising from horizontal biharmonic friction. The viscosity used to determine the strength of the tendency can be a general function of space yet it is constant in time. A namelist option exists that determines this viscosity as a local function of the grid spacing.

OTHER MODULES USED

       constants_mod
    diag_manager_mod
             fms_mod
     mpp_domains_mod
             mpp_mod
   ocean_domains_mod
       ocean_obc_mod
 ocean_operators_mod
ocean_parameters_mod
     ocean_types_mod
      ocean_util_mod
 ocean_workspace_mod

PUBLIC INTERFACE

ocean_bihcst_friction_init:
bihcst_friction:
delsq_velocity:
bihcst_viscosity_check:
bihcst_reynolds_check:

PUBLIC ROUTINES

  1. ocean_bihcst_friction_init

    DESCRIPTION
    Initialize the horizontal biharmonic friction module by registering fields for diagnostic output and performing some numerical checks to see that viscosity is set appropriately.


  2. bihcst_friction

    DESCRIPTION
    This subroutine computes the thickness weighted acceleration on horizontal velocity arising from horizontal biharmonic friction.


  3. delsq_velocity

    DESCRIPTION
    Subroutine computes the laplacian operator acting on velocity.


  4. bihcst_viscosity_check

    DESCRIPTION
    Subroutine to perform linear stability check for the biharmonic operator given a value for the horizontal biharmonic viscosity.


  5. bihcst_reynolds_check

    DESCRIPTION
    Subroutine to compute the biharmonic grid Reynolds number. Large Reynolds numbers indicate regions where solution may experience some grid noise due to lack of enough horizontal friction.


NAMELIST

&ocean_bihcst_friction_nml

use_this_module
Must be true to use this module. Default is false.
[logical]
debug_this_module
For debugging by printing checksums.
[logical]
abih
This is the value for the space-time constant biharmonic viscosity.
[real, units: m^4/sec]
velocity_mix_micom
If .true., then the viscosity is set according to a velocity scale times the cube of the grid spacing. It is based on an approach recommended by Eric Chassignet that is used in the Miami Isopycnal Model.
[logical]
vel_micom
Velocity scale that is used for computing the MICOM viscosity.
[real, units: m/sec]
eq_vel_micom
Velocity scale that is used for computing the MICOM viscosity within a latitude band surrounding the equator. This is useful for some models of enhanced equatorial resolution that can maintain numerical integrity in this region with less friction than outside the tropical band.
[real, units: m/sec]
eq_lat_micom
Equatorial latitude band (degrees) within which the MICOM viscosity is set according to eq_vel_micom.
[real]

REFERENCES

  1. R. J. Murray and C.J.C. Reason, A curvilinear version of the Bryan-Cox ocean model Journal Computational Physics (2002), vol 171, pages 1-46
  2. Elements of MOM (2012), S.M. Griffies

NOTES

The numerical implementation requires one call to mpp_update_domains if running the model with halo=1.

This scheme has been found to be faster than the Smagorinsky viscosity scheme. However, the algorithm here is less robust since it contains null modes in the terms associated with the sphericity of the earth. Hence, there may be flow configurations that are not dissipated.

The model can generally run with both Laplacian and biharmonic friction enabled at the same time. Such has been found useful for some eddying ocean simulations.

The numerical implementation in mom4p1 and mom5 does not include the sink due to partial bottom cells. This sink was implemented in mom2 and mom3 and mom4. It is not known how relevant this sink is.

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