# npzd Powell.in

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Powell NPZD Biological Model Input Script - npzd_Powell.in

The npzd_Powell.in file sets the parameters for the **Powell et al. NPZD** model. The name of this file is set by the BPARNAM keyword in the ocean.in file. A default npzd_Powell.in standard input ASCII file can be found in the **User/External** subdirectory of the ROMS source code. In order to include the **Powell et al. NPZD** model in ROMS you must set BPARNAM correctly and activate the NPZD_POWELL CPP option.

The Powell NPZD model equations and representative parameters may be found in:

**Notice:** Detailed information about ROMS input script file syntax can be found here.

## Biological Model Parameters

Input parameter units are specified within brackets ([ ])and default values are specified within braces ({ }).

- This switch to control the computation of npzd_Franks within nested and/or multiple connected grids. By default this switch is set to TRUE in mod_scalars.F for all grids. Ngrids values are expected. The
**user**has the option, for example, to compute the biology in just one of the nested grids. If so, this switch needs to be consistent with the dimension parameter NBT in mod_param.F. In order to make the model more efficient in memory usage, NBT(:) should be zero in such grids.

- Lbiology == T

- Maximum number of iterations to achieve convergence of the nonlinear solution.

- BioIter == 1

- Initial concentration for analytical uniform initial conditions, [millimole/m
^{3}]. It is only used when ANA_BIOLOGY is activated.

- BioIni(iNO3_) == 17.0d0 ! nitrate

BioIni(iPhyt) == 1.0d0 ! phytoplankton

BioIni(iZoop) == 1.0d0 ! zooplankton

BioIni(iSDet) == 1.0d0 ! detritus

- Fraction of shortwave radiation that is photosynthetically active, [nondimensional], {0.43d0}.

- PARfrac == 0.43d0

- Light attenuation due to seawater, [1/m], {0.067d0}.

- AttSW == 0.0067d0 ! k_ext

- Light attenuation due to phytoplankton, self-shading coefficient, [m
^{2}/millimole_N], {0.0095d0}.

- AttPhy == 0.0095d0 ! k_extP

- Phytoplankton, initial slope of P-I curve [m
^{2}/W], {0.025d0}.

- PhyIS == 0.025d0 ! alpha

- Nitrate uptake rate, [1/day], {1.5d0}.

- Vm_NO3 == 1.5d0 ! Vm

- Phytoplankton mortality rate to Detritus pool, [1/day], {0.1d0}.

- PhyMRD == 0.1d0 ! sigmaD

- Phytoplankton mortality rate to Nitrogen pool, [1/day], {0.0d0}.

- PhyMRN == 0.0d0 ! sigmaN

- Half-saturation for phytoplankton nitrate uptake [millimole_N m
^{-3}], {1.0d0}.

- K_NO3 == 1.0d0 ! k_N

- Ivlev constant for zooplankton grazing parameterization [Nondimensional], {14*0.06=0.84d0}

- Ivlev == 0.84d0

- Zooplankton grazing rate, [1/day], {0.52}.

- ZooGR == 0.52d0 ! R_m

- Zooplankton excretion efficiency to Detritus pool [nondimensional], {0.3d0}

- ZooEED == 0.0d0 ! gammaD

- Zooplankton excretion efficiency to Nitrogen pool [nondimensional], {0.3d0}

- ZooEEN == 0.3d0 ! gammaN

- Zooplankton mortality rate to Detritus pool, [1/day], {0.0d0}.

- ZooMRD == 0.145d0 ! zetaD

- Zooplankton mortality rate to Nitrogen pool, [1/day], {0.145d0}.

- ZooMRN == 0.0d0 ! zetaN

- Detritus remineralization rate, [1/day], {0.1d0}.

- DetRR == 1.03d0 ! delta

- Vertical sinking velocity for phytoplankton [m/day], {0.0d0}.

- wPhy == 0.0d0 ! wP

- Detrital sinking rate, [m/day], {8.0d0}.

- wDet == 8.0d0 ! wD

- Lateral, constant, harmonic/biharmonic horizontal diffusion of biological tracer for nonlinear model and adjoint-based algorithms: [1:NBT,Ngrids] values expected.

- Nudging/relaxation time scales, inverse scales will be computed internally: [1:NBT,Ngrids] values expected.

- TNUDG == 4*0.0d0 ! days

- Logical switches to specify which variables to consider on tracers point Sources/Sinks (like river runoff): [1:NBT,Ngrids] values expected.

- LtracerSrc == 4*F

- Logical switches to activate writing of biological tracers into history/average output file: [1:NBT,Ngrids] values expected.

- Hout(idTvar) == 4*T ! biological tracer

Hout(idTsur) == 4*F ! surface tracer flux

! idTvar(idbio(1))=iNO3_ Nitrate concentration

! idTvar(idbio(2))=iPhyt Phytoplankton biomass

! idTvar(idbio(3))=iZoop Zooplankton biomass

! idTvar(idbio(4))=iSdet Detritus concentration - As an example, if you only wanted to write
**zooplankton biomass**to the history and averages files you would do the following: - Hout(idTvar) == 2*F T F