WAMSI Node 6.1 - Offshore and coastal engineering and the effects of climate change - Wave model (past and present)

Brief description

This output is a wave model covering the Indian Ocean using the open source WAVEWATCH III (WW3) model. WW3 is the operational ocean wave prediction model of the US National Oceanic and Atmospheric Administration (NOAA). This was run from 1990 to 1998 (ongoing) and this overlaps with measured data from off Rottnest Island.

The Simulating WAve iNshore (SWAN) model was also used at particular regions of the WA coastline and a very high resolution grid for Yanchep Lagoon was also used.

Lineage

Statement: he wave models to be used in this part of the study have been set-up and are currently under validation. A model covering the Indian Ocean was setup using the open source WAVEWATCH III (WW3) model. WW3 is the operational ocean wave prediction model of the US National Oceanic and Atmospheric Administration (NOAA). It is a third generation wave model that solves the random phase spectral action density balance equation for wave number-direction spectra [1] (Tolman, 2002). The model includes wave propagation, growth due to wind, decay due to dissipation, breaking and whitecapping. It allows for multi-grid nesting and is design to run on a parallel computing environment, thus significantly increasing model run times. Hence, it is the most suitable model to simulate waves on an ocean basin scale.

WW3 grids used in the current study comprises of 4 model grids are used with different resolution:
(1) One degree resolution grid covers the entire southern Indian Ocean;
(2) 30 degree in the southern ocean where we receive majority of the storms; i.e. the generating region
(3) 30 degree in the along the outer WA coast; and (4) 10 degree grid encompasses the WA coast.

The model is forced by NCEP winds at 6 hourly intervals have a resolution of 2.5 degrees.

The WAVEWATCH III model has been run for the period 1990 to 1998 (and ongoing) and this period overlaps with the measured data off Rottnest Island (off the south-western Australia) located in 50 m of water. At this initial stage a very good correspondence has been achieved with the WW3 model predicting the majority of the major storms observed at the Rottnest wave rider buoy.
Although WW3 can simulate waves in the inshore, the Simulating WAve iNshore (SWAN) model provides a more suitable alternative for the coastal zone. The SWAN model focuses more on inshore wave processes, like wave setup and diffraction. A further advantage of the SWAN models is it can be run on an unstructured grid. This means that areas of interest can be modeling in finer resolution without the compromise of significantly increased model run times. We have nested a number of high resolution local SWAN wave models, covering particular regions of the WA coastline, into the relatively coarse Indian Ocean WW3 model.

The model grid for the Perth Metropolitan area is shown in thumbnail, along with the very high resolution grid for Yanchep Lagoon.

[1] Tolman, H.L., 2002. Validation of WAVEWATCH III version 1.15 for a global domain. NOAA / NWS / NCEP / OMB Technical Note Nr. 213, pp. 33.