Module ocean_shortwave_gfdl_mod

OVERVIEW

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

OTHER MODULES USED

          axis_utils_mod
           constants_mod
        diag_manager_mod
       field_manager_mod
                 fms_mod
                 mpp_mod
time_interp_external_mod
       ocean_domains_mod
    ocean_parameters_mod
         ocean_types_mod
     ocean_workspace_mod

PUBLIC INTERFACE

PUBLIC ROUTINES

1. ocean_shortwave_gfdl_init

   DESCRIPTION

   Initialization for the shorwave module

   
   
   

2. sw_source_gfdl

   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)" If the shortwave penetration routine is activated but Chlorophyll is not being read from data, then that implies that an ecological model is being used to determine chlorophyll concentration. In this case, the shortwave penetration is calcualted using the algorithm of Manizza, M., C Le Quere, A. J. Watson, and E. T. Buitenhuis (2005) Bio-optical feedbacks among phytoplankton, upper ocean physics and sea-ice in a global model. Geophys. Res. Let. 32, L05603, doi:10.1029/2004GL020778. This algorithm assumes that all infrared light is absorbed in the top level. It separates visible light into equal portions of red and blue bands, treating separately absorption by water and chlorophyll. If the Chlorophyll is read from data, then we generally use the Morel and Antoine optics scheme. Here, we take their approach for computing a vertical profile based on the surface Chlorophyll. However, one may also wish to use the Manizza scheme with surface Chlorophyll data. In this case, we assume the surface Chlorophyll concentration is the same throughout the depth. This assumption is not generally good, but it does provide for a simple means of using Manizza etal scheme with Chlorophyll data. Note that GFDL scientists prefer Manizza etal for use with prognostic 3d models. NOTE: Determine depths to T-points and W-points. This code is needed in particular for GEOPOTENTIAL, since depth_zwt and depth_zt for this coordinate do not include the surface height undulations. For the shortwave calculation, we wish to include the depth level undulations, unless enable sw_morel_fixed_depths=.true.

   
   
   

3. sw_morel

   DESCRIPTION

   Solar shortwave energy penetrates below the ocean surface and is aborbed by water and organic matter (both particulate and dissolved). This routine estimates fraction of shortwave penetration using chlorophyll-a. Absorbtion of shortwave radiation in the water assumes energy partitions between three exponentials: The first exponential is for wavelength > 0.75 um (microns) and assumes a single attenuation of 0.267 m if the "zenith_angle" is 0. Presently the code assumes a zero zenith angle, but this could be modified easily. The second and third exponentials represent a parameterization of the attenuation coeficient for light between 300 um and 750 um in the following form: E(z) = E(0) * [V1 * exp(z/efold1) + V2 * exp(z/efold2)] with z < 0 the ocean depth Here, V1+V2=1 represent the partitioning between long (V1) and short (V2) wavelengths between 300 um and 750 um. Thoughout most of the ocean V1<0.5 and V2>0.5. The "efold1" and "efold2" are the efolding depth of the long and short visable and ultra violet light. Throughout most of the ocean efold1 should not exceed 3 m while the efold2 will vary between 30 m in oligotrophic waters and 4 m in coastal regions. All of these constants are based on satellite estimates of chlorophyll a and taken from Morel and Antoine (JPO 1994, (24) 1652-1664). If the thickness of the first ocean level "dzt(1)" is 50 meters, then shortwave penetration does not do much. However, for higher 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.

   
   
   

4. sw_morel_mom4p0

   DESCRIPTION

   As in sw_morel, but uses the MOM4.0 algorithm to re-compute a k-level. The recomputation is not needed, it can be costly, and produces no physically significant differences. This routine is retained for legacy only and it is not otherwise recommended.

   
   
   

NAMELIST

REFERENCES

NOTES