PUBLIC INTERFACE ~ PUBLIC ROUTINES ~ NAMELIST

Module ocean_advection_velocity_mod

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

OVERVIEW

Advection velocity components for tracer and momenta transport, with options for B-grid or C-grid.

The module computes the horizontal and vertical components to the advection velocity on the face of tracer and velocity cells. Options are provided for either the B-grid or C-grid. The three velocity components are related by continuity. All components are density weighted, and the horizontal components are thickness weighted. Some diagnostics related to fluid mass transport classified according to both depth and density classes are also computed.

OTHER MODULES USED

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

PUBLIC INTERFACE

ocean_advection_velocity_init:
ocean_advection_velocity:
check_vert_cfl_blobs:
read_advect_velocity:
inflow_nboundary_init:
ocean_advection_velocity_end:

PUBLIC ROUTINES

  1. ocean_advection_velocity_init

    DESCRIPTION
    Initialize the advection velocity module


  2. ocean_advection_velocity

    DESCRIPTION
    Compute thickness weighted and density weighted advection velocity components for the B-grid on the T-cells and U-cells.


  3. check_vert_cfl_blobs

    DESCRIPTION
    This routine is useful to check for strong vertical motions in the presence of Lagrangian blobs. The CFL check is the same as in the module ocean_adv_vel_diag.F90, but we have more local control here so it is useful in the development stages of the blobs.


  4. read_advect_velocity

    DESCRIPTION
    For reading in the advection velocity components. Assume that the advection velocity components read in from a file are in units of meter/sec and placed on the T-cell faces, as in a C-grid ocean model. This routine assumes that the read-in velocity components already have the proper masking. The main application of this routine is for developing idealized test cases for tracer advection.


  5. inflow_nboundary_init

    DESCRIPTION
    Initialize the advection velocity used for specifying a nonzero southward inflow introduced to the domain from the northern boundary.


  6. ocean_advection_velocity_end

    DESCRIPTION
    Write a restart if necessary


NAMELIST

&ocean_advection_velocity_nml

debug_this_module
For debugging.
[logical]
inflow_nboundary
For adding an inflow velocity from the northern boundary. Default is inflow_nboundary=.false.
[logical]
read_advection_velocity
For reading in a file with specified zonal, meridional, and vertical components to the advection velocity. The file should have velocity at the east face of T-cell, north face, and bottom, just as on a C-grid. The units should be m/s for each component. MOM then multiplies but the appropriate thickness and density factors to generate transport for use in the model. Default read_zonal_advection_velocity=.false.
[logical]
constant_advection_velocity
When reading in the advection velocity components, we may choose to keep them constant in time. This facilitates idealized tests of tracer advection. Default constant_advection_velocity=.false.
[logical]
max_advection_velocity
This is a check value used to determine if the time steps will result in linearly stable advection. If set to a number < 0, then model will estimate the value as a function of maximum grid size. Note that this time step check is not rigorous, and it depends on the details of the advection scheme. Nonetheless, it provides some useful warning for setting the time steps in the model.
[real, units: meter/sec]

REFERENCES

  1. R.C. Pacanowski and S.M. Griffies The MOM3 Manual (1999)
  2. S.M. Griffies, M.J. Harrison, R.C. Pacanowski, and A. Rosati A Technical Guide to MOM4 (2003)
  3. S.M. Griffies: Elements of MOM (2012)

NOTES

The expressions for the horizontal components for tracer advection allow for a proper conversion between pressure work and buoyancy.

The B-grid remapping operators are derived from considerations of linear interpolation and volume conservation. A "remapping error" is computed to determine consistency between the tracer and velocity grid advection velocities. This error is roundoff only for cases where the horizontal tracer and velocity grids are linearly related, as is the case for the spherical coordinate version of MOM. The tripolar version of MOM does not have tracer and velocity grids related linearly, and so the "remapping error" is nontrivial. The significance of this error is unclear. No adverse effects have been identified.

The vertical velocity components for both the tracer and velocity cells are diagnosed via continuity (either volume or mass conservation depending on the use of the Boussinesq or non-Boussinesq versions of MOM).

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