Integrated Coastal Zone Management
Coastal Water Quality Simulation
Coastal & Marine Systems Modeling
ROMS/TOMS: Regional Ocean Modeling System

The Regional Ocean Model System ( is a free-surface, hydrostatic, primitive equation ocean model that uses stretched, terrain-following coordinates in the vertical and orthogonal curvilinear coordinates in the horizontal.

Initially, it was based on the S-coordinate Rutgers University Model (SCRUM) described by Song and Haidvogel (1994). ROMS was completely rewritten to improve both its numerics and efficiency in single and multi-threaded computer architectures. It also was expanded to include a variety of new features including:

  • high-order advection schemes;
  • accurate pressure gradient algorithms;
  • several subgrid-scale parameterizations;
  • atmospheric, oceanic, and benthic boundary layers;
  • biological modules;
  • radiation boundary conditions;
  • and data assimilation.

Test case: Model implementation for the Hamriyah Free Economic Zone, UAE,
Reverse Osmosis desalination plant, inner harbor outfall scenario

Model Grid
The model uses Cartesian grid with horizontal resolution of 10 m. Domain size: 400x400 grid points with 7 vertical levels. Sigma (terrain-following) levels are uniformly distributed.

Topography is extracted from prepared bathymetry file for HFZ domain. Land/sea masking for rho, u, v and psi grids are calculated accordingly. Grid parameters: pm, pn, x_rho, y_rho, x_psi, y_psi, x_u, y_u, x_v, y_v are extracted from analytical grid calculated by the model using ANA_GRID option. Coriolis factor is set to constant f=0.0001 s-1

Model options
for setup with open boundary conditions, analytical tides, analytical salinity input and mm5 surface forcing:

ANA_BSFLUX Analytical kinematic bottom salinity flux. ANA_BTFLUX Analytical kinematic bottom temperature flux.
ANA_FSOBC Analytical free-surface boundary conditions. ANA_INITIAL Analytical initial conditions.
ANA_M2OBC Analytical 2D momentum boundary conditions. ANA_PSOURCE Analytical point sources and sinks.
ANA_TOBC Analytical tracers boundary conditions. ASSUMED_SHAPE Using assumed-shape arrays.
AVERAGES Writing out time-averaged fields AVERAGES_AKS Writing out time-averaged vertical S-diffusion.
AVERAGES_AKT Writing out time-averaged vertical T-diffusion. BULK_FLUXES Surface bulk fluxes parametererization.
DJ_GRADPS Parabolic Splines density Jacobian (Shchepetkin, 2002). DOUBLE_PRECISION Double precision arithmetic.
EASTERN_WALL Wall boundary at Eastern edge. EMINUSP Compute Salt Flux using E-P.
LMD_BKPP KPP bottom boundary layer mixing. LMD_CONVEC LMD convective mixing due to shear instability.
LMD_MIXING Large/McWilliams/Doney interior mixing. LMD_NONLOCAL LMD convective nonlocal transport.
LMD_RIMIX LMD diffusivity due to shear instability. LMD_SKPP KPP surface boundary layer mixing.
LONGWAVE_OUT Compute outgoing longwave radiation internally. MASKING Land/Sea masking.
MIX_GEO_TS Mixing of tracers along geopotential surfaces. NONLINEAR Nonlinear Model.
NONLIN_EOS Nonlinear Equation of State for seawater. NORTH_FSCHAPMAN Northern edge, free-surface, Chapman condition.
NORTH_M2FLATHER Northern edge, 2D momentum, Flather condition. NORTH_M3RADIATION Northern edge, 3D momentum, radiation condition.
NORTH_TRADIATION Northern edge, tracers, radiation condition. _OPENMP OpenMP parallel shared-memory directives.
POWER_LAW Power-law shape time-averaging barotropic filter. PROFILE Time profiling activated .
!RST_SINGLE Double precision fields in restart NetCDF file. SALINITY Using salinity.
SOLVE3D Solving 3D Primitive Equations. SOUTH_FSCHAPMAN Southern edge, free-surface, Chapman condition.
SOUTH_M2FLATHER Southern edge, 2D momentum, Flather condition. SOUTH_M3RADIATION Southern edge, 3D momentum, radiation condition.
SOUTH_TRADIATION Southern edge, tracers, radiation condition. SPLINES Conservative parabolic spline reconstruction.
STATIONS Writing out station data. TS_A4HADVECTION Fourth-order Akima horizontal advection of tracers.
TS_A4VADVECTION Fourth-order Akima vertical advection of tracers. TS_DIF2 Harmonic mixing of tracers.
TS_PSOURCE Tracers point sources and sinks. UV_ADV Advection of momentum.
UV_COR Coriolis term. UV_U3HADVECTION Third-order upstream horizontal advection of 3D momentum.
UV_C4VADVECTION Fourth-order centered vertical advection of momentum. UV_QDRAG Quadratic bottom stress.
UV_PSOURCE Mass point sources and sinks. VAR_RHO_2D Variable density barotropic mode.
WEST_FSCHAPMAN Western edge, free-surface, Chapman condition. WEST_M2FLATHER Western edge, 2D momentum, Flather condition.
WEST_M3RADIATION Western edge, 3D momentum, radiation condition. WEST_TRADIATION Western edge, tracers, radiation condition.
WET_DRY Wetting and drying activated.

Initial conditions   Initial temperature and salinity are set to background values. Background temperature T0 = 25C. Background salinity S0 = 40 psu. Initial velocities and sea surface height are set to zero.

Lateral boundary conditions   In scenario with open boundary conditions, South, North and West boundary have prescribed radiation condition for tracers and 3D momentum, Chapman condition for sea surface height and Flather conditions for 2D momentum. Tides are prescribed on the northern boundary with analytical function: ssh = A * sin( 2 * pi * time / (12 * 3600) ), where A= -0.05m (-0.9 m for scenario "HFZ tides MM5").
No velocities are prescribed on the lateral boundaries, while tracer values are set to background values. In scenario with closed boundary conditions, walls are defined for all lateral boundaries (zero velocities, no radiation).

Surface boundary conditions   In scenarios with MM5 surface forcing, real-time MM5 forecast output is used to force the model. MM5 timeseries at ROMS HFZ longitude/latitude are extracted for 24 hours, output every 60 minutes. (Note: maximal resolution of MM5 output is 3 km, while ROMS HFZ domain extent is 4km). Following variables are extracted from MM5 and interpolated on ROMS HFZ grid:

  • PSTARTCRS, PTORP, PP - pressure
  • T2 - temperature at 2 m
  • Q2 - humidity at 2 m
  • U10 - u-wind at 10 m
  • V10 - v-wind at 10m
  • SWDOWN - shortwave downward radiation
  • LWDOWN - longwave downward radiation
  • RAIN_CON, RAIN_NON - convective and non-convective rain
Surface fluxes are calculated within the model using bulk formulas (BULK_FLUXES option). Evaporation is calculated in the model and saved as output variable.

Brine input   Brine input in the model is introduced as salinity point source in the HFZ port channel. Position of the source is at the land/sea boundary (coordinates i=203, j=158). Input flux equals to 0.5 m3/s with brine salinity of 60 psu. Salinity input is equally distributed between levels 3, 4 and 5. Available scenarios have constant salinity input. Time-dependant salinity release was tested.

ROMS scenarios   ROMS results are organized into ROMS scenarios. Each scenario refers to 24 hours period of model output. Additional 5 days scenario named "TOTAL" are given for overview consisting from joined 5 sequential model outputs. ROMS scenario displays following ocean variables: temperature, salinity, 3D currents, salinity increase, sea surface height, timeseries of evaporation, input of brine and vertical averaged salinity at the observational station. Salinity increase is defined as (salinity - default_salinity)/default_salinity*1000.

MM5 coupling   Each ROMS scenario with surface forcing has corresponding MM5 scenario where atmospheric conditions are displayed for the ROMS domain. The extraction of MM5 data for ROMS domain can be done automatically by saving MM5 timeseries into the MM5 domain station, which can be read by a ROMS preprocessing function that interpolates MM5 data on the ROMS grid and create atmospheric forcing fields in the real-time.

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