WRF-ARW Forecast Model

Weather Research and Forecast model has been designed for operational forecast and atmospheric research, developed by NCAR (The National Centre for Atmospheric Research, USA). The scope of this model is wide, from the study of meteorological phenomena (convection, baroclinic waves, etc.) to the operational mesoscale forecasts and regional atmospheric circulation of the order of hundred meters to several thousand kilometres. The advantage of the meteorological model is that it allows calculation of the value of meteorological parameters at the entire modeling area, including those places where there are no measurements.

WRF-ARW boundary and initial conditions are interpolated from GFS (0.25 degrees) global model results. Our setup is covering western region of Australia at horizontal resolution of 10km with 2-way nested 2 km resolution model domain for wider Perth area. Model outputs are used as a forcing input for our ROMS ocean model. For certain locations we save model outputs more frequent in time (actually at each model time step – 60s for big domain and 12s for nested). Those variables are presented at the Timeseries section.

List of WRF model output parameters provided on Costal Oceanography website:

Air temperature: the value is given in °C and refers to the temperature 2m ​​above ground.

Pressure: mean Sea Level Pressure given in hPa.

Wind: wind speed (m/s) and direction at 10m height.

Precipitation: Given in millimeters and represents the accumulated total precipitation for the last 3hours.

Reflectivity: a reflectivity of the atmosphere measured in dBZ. The most common value for convective cloudiness reflexivity is above 35 dBZ. The higher the dBZ value, the stronger the convective processes (which may later lead to precipitation).

MCAPE: Mean Available Convective Potential Energy (CAPE) is one of the measures of tropospheric instability. Generally, the higher the MCAPE value, the greater the probability of development of thunderstorms.


ROMS Forecast Model

Numerical model ROMS (Regional Ocean Modelling System) is a 3D, free-surface oceanographic model discretized with a terrain-following vertical coordinate system (class of sigma-coordinate models). It solves Navier-Stokes equation with Boussinesq approximation and fluid incompressibility assumption. Model has been widely applied in many applications ranging from planetary scales down to the scales of estuarine environments. Beside calculations of water temperature, ocean currents, salinity, and sea surface height, it uses advanced turbulence closure scheme describing sub-grid processes and enabling applications such as sediment transport modeling, etc.

Lateral boundary conditions for outer ROMS model are daily updated from the global HYCOM model forecasts. Atmospheric forcing in our current ROMS setup use outputs from our local WRF-ARW model output fields. Our model setup covers western region of Australia at ~ 1.5 – 2.5 km horizontal resolution for the big model domain with additional downscale for wider Perth region at 500 m resolution. We archive our variables hourly, however for certain locations even more frequent outputs are provided (10 minute outputs).

List of ROMS model output parameters provided on Costal Oceanography website:

Surface currents: surface currents velocity (m/s) and direction are shown with vector (arrow). Unit vector length is shown on the map legend. Currents velocity less than 5 cm/s are not plotted. Colors under the vectors represent Sea Surface Temperature (°C).

Sea temperature: represent surface temperature defined in degrees Celsius (°C).

Salinity: dimensionless variable, defined as the total amount of dissolved salts in seawater in ‰, when all carbonates are turned into oxides, bromides and jodides into chlorides and all organic matter completely oxidised.


NOAA WAVEWATCH III® Model

WAVEWATCH III® is a third generation wave model developed at NOAA/NCEP in the spirit of the WAM model. The model uses a regularly spaced longitude-latitude grid (longitude and latitude increment do not need to be equal) and, optionally, a Cartesian grid. It is set up for traditional one-way nesting, where model grids are run as separate models consecutively, starting with the models with the lowest spatial resolution. Wave energy spectra are discretized using a constant directional increment (covering all directions), and a spatially varying wavenumber grid. The latter grid corresponds to an invariant logarithmic intrinsic frequency grid. Global WAVEWATCH III® model setup is run 4 times per day, giving 126 hours of forecast and covering 77°S - 77°N at 0.5°x0.5° horizontal resolution. It is forced with NOAA operational GFS atmospheric model.

List of WAVEWATCH III® model output parameters provided on Costal Oceanography website:

Significant wave height (m): measure for the wave height, and closely corresponds to what a trained observer would consider to be the mean wave height. Note that the highest wave height of an individual wave will be significantly larger.

Wave direction (°): parameter defined as the mean direction in the frequency bin corresponding to peak period Tp.

Wave peak period (s): Tp (in seconds) is a period (the time between waves) associated with the locally generated wind sea (in cases with strong local winds) or the dominant wave system (swell) that is generated elsewhere. Note that this peak period field shows discontinuities. These discontinuities can loosely be interpreted as swell fronts, although in reality many swell systems overlap at most locations and times.


SWAN Model

SWAN is a third-generation wave model, developed at Delft University of Technology, that computes random, short-crested wind-generated waves in coastal regions and inland waters. The model is a Eulerian formulation of the discrete action balance equation (Booji et al., 1996). It is setup to cover a frequency range of 45 frequency bands logarithmically scaled from 0.03 to 2 Hz and 45 directional bands, giving the model a directional resolution of 8°. Three model grids were nested together in order to minimize computation time while maximizing the spatial resolution, with the finest grid having a resolution of ~500 m by ~500 m.

The model is forced using 1-hourly GFS wind fields at a spatial resolution of 0.25° by 0.25°. Boundary wave conditions are obtained from NOAA’s global WaveWatch III Multi-grid wave model with a spatial resolution of 30 arc-min.

SWAN model output parameter provided on Costal Oceanography website:

Significant wave height (m): measure for the wave height, and closely corresponds to what a trained observer would consider to be the mean wave height. Note that the highest wave height of an individual wave will be significantly larger.