Wave forecast model upgrades

MetOcean Solutions has released an upgrade in all regional and local scale operational wave models. This upgrade brings improvements to model skill throughout the forecast horizon.

Wave models are used to simulate the physical processes occurring in wave growth, wave breaking and wave propagation. The processes involved in describing the input from the wind and the dissipation from wave breaking are collectively referred to as the model source terms.

“New source terms (called ST6) have recently been implemented in the official release of the Simulating WAves Nearshore (SWAN) spectral wave model,” says MetOcean Solutions’ Senior Physical Oceanographer Dr Rafael Guedes. “These terms are based on field observations and incorporate some important new physical features, including airflow separation under strong wind forcing, swell dissipation and a better description of breaking dissipation.

“Our operational services rely extensively on SWAN. The new source terms represent a great improvement in the physical representation of wave generation and dissipation within our regional and local scale wave models.

“We have carefully calibrated and validated all our regional operational domains with the new physics,” continues Rafael. “Comparison against satellite altimeters and in-situ wave observations showed consistent improvements in our models across all major areas.”

Figure 1 and Figure 2 below show percentage changes in Root-Mean-Square-Deviation (RMSD) and scatter index (SI), two commonly-used measurements of wave model skills. Overall improvements are apparent as highlighted by the blue colours, with up to 30% decrease in RMSD and 11% decrease in SI with ST6 in some of these areas. The improvements are shown in more detail for MetOcean’s 5-km SWAN grid in Australia Northwest Shelf in Figures 3 and 4.

 
Figure 1. Percentage changes in Root-Mean-Square-Deviation (RMSD) between operational SWAN domains run with old and new SWAN physics. Blue and red indicate reduction and increase in RMSD respectively.

Figure 1. Percentage changes in Root-Mean-Square-Deviation (RMSD) between operational SWAN domains run with old and new SWAN physics. Blue and red indicate reduction and increase in RMSD respectively.

 
 
Figure 2. Percentage changes in Scatter Index (SI) between operational SWAN domains run with old and new SWAN physics. Blue and red indicate reduction and increase in SI respectively.

Figure 2. Percentage changes in Scatter Index (SI) between operational SWAN domains run with old and new SWAN physics. Blue and red indicate reduction and increase in SI respectively.

 
 
Figure 3. Validation against satellite altimeters of MetOcean Solutions’ 5km Australia Northwest Shelf SWAN domain using the old physics source terms. Overall scatter diagram and scatter density are shown at the top. Model bias and RMSD are presented at the bottom.

Figure 3. Validation against satellite altimeters of MetOcean Solutions’ 5km Australia Northwest Shelf SWAN domain using the old physics source terms. Overall scatter diagram and scatter density are shown at the top. Model bias and RMSD are presented at the bottom.

 
 
Figure 4. Validation against satellite altimeters of MetOcean Solutions’ 5km Australia Northwest Shelf SWAN domain using the new ST6 physics source terms. Overall scatter diagram and scatter density are shown at the top. Model bias and RMSD are presented at the bottom.

Figure 4. Validation against satellite altimeters of MetOcean Solutions’ 5km Australia Northwest Shelf SWAN domain using the new ST6 physics source terms. Overall scatter diagram and scatter density are shown at the top. Model bias and RMSD are presented at the bottom.

 

At MetOcean Solutions, a division of MetService, we continuously improve our models with the current state-of-the-art science to ensure the highest possible performance.