PUBLIC INTERFACE ~ PUBLIC ROUTINES ~ NAMELIST

Module ocean_lap_tracer_mod

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

OVERVIEW

Thickness weighted and density weighted time tendency for tracer from lateral laplacian diffusion.

This module computes lateral laplacian diffusion of a tracer. There are two main options. (1) The lateral tracer fluxes can be aligned with the z-coordinate surfaces, in which case the fluxes must be approximated if (i) we use non-geopotential vertical coordinates, (ii) next to partial bottom step topography. This form of the diffusion is not recommended since it can lead to the creation of spurious extrema. (2) The lateral tracer fluxes can be aligned surfaces of constant vertical coordinate. In this case the fluxes are no longer strictly "horizontal." However, the operator is simpler and it ensures that no suprious extrema are created. It is for this reason that the simpler operator is preferred. The diffusivity 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 diffusivity 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_workspace_mod

PUBLIC INTERFACE

ocean_lap_tracer_init:
lap_tracer:

PUBLIC ROUTINES

  1. ocean_lap_tracer_init

    DESCRIPTION
    Initialize the laplacian diffusion module by registering fields for diagnostic output and performing some numerical checks to see that diffusivity is set appropriately.


  2. lap_tracer

    DESCRIPTION
    This function computes the thickness weighted and density weighted time tendency for tracer from lateral laplacian diffusion.


NAMELIST

&ocean_lap_tracer_nml

use_this_module
Must be true to use this module. Default is false.
[logical]
horz_z_diffuse
To compute diffusion along surfaces of constant depth. This operation must necessarily be approximate for the two cases (i) non-geopotential vertical coordinates, (2) next to partial bottom step topography. There are cases where use of this operator can lead to spurious creation of extrema due to truncation errors associated with the "slope" term. For most cases where lateral diffusion is required, we will want it to be "diffusive" in the sense that no extrema are created. So the default is horz_z_diffuse=.false. The option to use horz_z_diffuse=.true. is maintained for legacy purposes alone.
[logical]
horz_s_diffuse
To compute diffusion along surfaces of constant vertical s-coordinate. This operation is ensured of obtaining a smoothing operator that does not create extrema. It is the default for this reason.
[logical]
alap
This is the value for the space-time constant Laplacian diffusivity.
[real, units: m^2/sec]
tracer_mix_micom
If .true., then the diffusivity is set according to a velocity scale times the grid spacing. It is based on an approach recommended by Eric Chassignet that is used in the Miami Isopycnal Model (MICOM).
[logical]
vel_micom
Velocity scale that is used for computing the MICOM diffusivity.
[real, units: m/sec]
read_diffusivity_mask
Allows for reading of a mask that to apply diffusivity only in selected regions. Default read_diffusivity_mask=.false.
[logical]
verbose_init
For verbose writes during initialization
[logical]

NOTES

The numerical implementation requires no calls to mpp_update_domains.

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