PUBLIC INTERFACE ~ PUBLIC ROUTINES ~ NAMELIST

Module ocean_shortwave_jerlov_mod

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

OVERVIEW

This module returns thickness and density weighted temperature tendency [kg/m^3 * deg C *m/sec] from penetrative shortwave heating.

Compute thickness and density weighted tendency [deg C *m/sec *kg/m^3] of temperature associated with penetrative shortwave heating in the upper ocean. This module ussumes a simple double exponential decay law. The e-folding depth may vary spatially and temporaly. The exponentials represents a parameterization of the attenuation coefficient for light between 300 um and 750 um in the following form: E(z) = E(0) * (r1*exp(-z/efold1) + (1-r1)*exp(-z/efold2)) with z > 0 the ocean depth The "efold" is the efolding depth of the long and short visable and ultra violet light. efold will vary between 30 m in oligotrophic waters and 4 m in coastal regions. If the thickness of the first ocean level "dzt(1)" is 50 meters, then shortwave penetration does not do much. However, for finer vertical resolution, such as dzt(1) = 10 meters commonly used in ocean climate models, the effect of shortwave heating can be significant. This can be particularly noticable in the summer hemisphere. Radiation at the bottom is set to zero, hence the remaining radiation at the bottom of the deepest ocean cells is totally absorbed by these cells. This implies, that partial cells need not to be considered explicitly. Radiation at tracer depth within these cells is not set to zero. This differs from ocean_shortwave_gfdl and ocean_shortwave_csiro and reduces slightly the bouyancy forcing to the mixing layer in the kpp-scheme, if surface mixing goes down to the bottom.

OTHER MODULES USED

           constants_mod
                 fms_mod
                 mpp_mod
time_interp_external_mod
       ocean_domains_mod
    ocean_parameters_mod
         ocean_types_mod
     ocean_workspace_mod

PUBLIC INTERFACE

ocean_shortwave_jerlov_init:
sw_source_jerlov:

PUBLIC ROUTINES

  1. ocean_shortwave_jerlov_init

    DESCRIPTION
    Initialization for the shortwave module


  2. sw_source_jerlov

    DESCRIPTION
    Add short wave penetrative heating to T_prog(index_temp)%th_tendency. Note that the divergence of shortwave for the first level "div_sw(0)" is compensating for the effect of having the shortwave component already included in the total surface tracer flux "stf(i,j,temp)"


NAMELIST

&ocean_shortwave_jerlov_nml

use_this_module=
Must be .true. to run with module. Default is false.
[logical]
sw_frac_top
The fraction of shortwave radiation that should be incorporated into the sw_source array at k=1. The generic treatment in MOM is to assume that shortwave radiation is already contained inside the T_prog(index_temp)%stf field. Hence, to avoid double counting, sw_frac(k=0)=sw_frac_top should=0.0. If one removes shortwave from stf, then set sw_frac_top=1.0.
[real]
f_vis_in
F_vis is the amount of light in the shortwave versus the long wave. F_vis=0.54 on sunny days and F_vis=0.60 on cloudy days. With override_f_vis = .true. F_vis is defined from f_vis_in. We believe, that this effect is in the first exponential in Paulson and Simpson (1977). The default is f_vis_in=1., instead of .57 but it is still possible to define this quantity.
[real]
rpart_in
rpart_in = (0..1)
[real]
coef1_in

[real, units: meter]
coef2_in

[real, units: meter]
override_coeff
With override_coeff = .true. rpart_in, coef1_in, coef2_in specify the parameters for the double exponential. The default is .false..
[logical]
override_f_vis
With override_f_vis = .true. F_vis is defined from f_vis_in, otherwise it is the shortwave versus the long wave amount of light. The default is .true.
[logical]
zmax_pen
Maximum depth of penetration of shortwave radiation. Below this depth, shortwave penetration is exponentially small and so is ignored.
[real, units: meter]
baltic_optics, jerlov_1, jerlov_2, jerlov_3, jerlov_1a, jerlov_1b
Logical switch to select a watertype. Default=.false.. The model stops, if none is selected and override_coeff=.false..
[logical]
enforce_sw_frac
To ensure the shortwave fraction is monotonically decreasing with depth.
[logical]
sw_pen_fixed_depths
To compute penetration assuming fixed depths via Grd%zw(k) depths. This is strictly incorrect when have undulating free surface or generatlized vertical coordinates. This option is here for purposes of legacy, as this was done in MOM4.0 versions. It saves some compute time if the surface elevation is small compared with the upper cells' thickness. The default is .false.
[logical]
debug_this_module
For debugging purposes.
[logical]

REFERENCES

  1. Jerlov (1968) Optical Oceanography Elsevier Press
  2. Paulson and Simpson (1977) Irradiance measurements in the upper ocean Journal of Physical Oceanography vol 7 pages 952-956
  3. Rosati and Miyakoda (1988) A General Circulation Model for Upper Ocean Simulation Journal of Physical Oceanography vol 18 pages 1601-1626.

NOTES

The efolding depth is depth independent.

Simpson and Dickey (1981) and others have argued between one and two exponentials for light between 300 um and 750 um. With vertical grid resolution of 5 meters or finer for the upper 20 meters, a second exponential will make a difference.

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