Simplified Model Domain - 2D

This page provides instructions on how to build a simplified two-dimensional version of the Salish Sea model. The two-dimensional model is based on a simplifed bathymetry profile along the domain’s thalweg. A simplified model allows for quick sensitivity tests of mixing parametrizations and resolution.

New NEMO Configuration

The first step is to create a new NEMO configuration. Here we will define parameters such as number of grid points and resolution. These instructions explain how to create a new configuration called SalishSea2D

  1. In NEMO-code/NEMOGCM/CONFIG, create directory for the new configuration.

cd NEMO-code/NEMOGCM/CONFIG
mkdir SalishSea2D

2. Create a cpp_SalishSea2D.fcm file and place it the configuration directory. Add a key for the new configuration and any other keys you require. For example,

cd SalishSea2D
ls cpp_SalishSea2D.fcm
bld::tool::fppkeys  key_bdy key_vectopt_loop   key_dynspg_ts key_ldfslp    key_vvl
key_diainstant key_mpp_mpi key_netcdf4 key_nosignedzero key_traldf_c2d key_dynldf_c3d
key_tide key_zdfgls key_iomput key_salishsea2D

3. Add configuration source files to SalishSea2D/MY_SRC. You need at least two modified source files: par_oce.F90 and par_SalishSea2D.h90. In par_oce.F90, add a case for dealing with the new configuration key:

#elif defined key_salishsea2D
   !!---------------------------------------------------------------------
   !!   'key_salishsea2D':                    Strait of Georgia: 2D
   !!---------------------------------------------------------------------
#             include "par_SalishSea2D.h90"

4. Specify choices in domain size, grid and resolution by editing par_SalishSea2D.h90. For example, these choices will set up a simplified grid 1100 by 10 by 40 grid points with 500 m resolution. See the NEMO documentation for details on parameter choices.

jpidta  = 1100,        &  !: first horizontal dimension > or = to jpi
jpjdta  = 10,          &  !: second                     > or = to jpj
jpkdta  = 40,          &  !: number of levels           > or = to jpk

jphgr_msh = 2          &  !: type of horizontal mesh
!                         !  = 2 f-plane with regular grid-spacing

ppgphi0  = 0.0_wp,         &  !: latitude for the Coriolis or Beta parameter (jphgr_msh = 2 or 3)

ppe1_m   = 500,   &  !: zonal      grid-spacing (meters )
ppe2_m   = 500       !: meridional grid-spacing (meters )
  1. Add SalishSea2D OPA_SRC to the last line of NEMO-code/NEMOGCM/CONFIG/cfg.txt

6. Try compiling with this new configuration. For example, on salish

cd NEMO-code/NEMOGCM/CONFIG
./makenemo -n SalishSea2D -m salish -j8

Note: This configuration has been added to the NEMO-code repository.

Bathymetry

A simplifed 2D bathymetry was created by smoothing the bathymetry along the thalweg. See Generate_2D_bathy.ipynb

Initial Conditions

Initial conditions for temperature and salinity were taken from model 2003 spin-up. The velocities are initialized to zero values. Winter and summer stratifications were created using Generate_2D_T+S.ipynb. Note that a test run with basic namelists was used to create the 2D mesh_mask.nc. This file was used to ensure the initial temperature and salinity covered the full 2D domain.

Tides

Tidal elevations are based on the 3D model tides, averaged across the mouth of the Strait of Juan de Fuca. Tidal currents for U are also based on 3D tidal currents, averaged across the boundary. Tidal currents for V are ignored. Some adjustments to the tidal currents are made to enforce rapid velocties over the sill since the horizontal constriction is not present in the 2D domain. See Generate_2D_Tides.ipynb for generation of tide forcing files.

River

A simple representation of the Fraser River was added to replace mixed stratification. A constant flow rate was used. Details in Generate_rivers_forcing.ipynb.

Namelists

The namelists need to be modified to reflect the new forcing files and boundary conditions. See /data/nsoontie/MEOPAR/2Ddomain/namelists.

Changes in Resolution

To be added