The eva‎luation and Development of Nonlinear Quadruplet Wave-Wave Interaction Term for Shallow Waters in Third-Generation Wave Models

12/10/2023 12:00:00 AM

In this research, the well-known WAM-Cycle4, known as ST3, and the newest ST6 package in WAVEWATCH-III model were employed combined with ERA5 wind data over the Persian Gulf and Gulf of Oman. In order to model the wave height appropriately over the study area in comparison with both in-situ and satellite observations, new combined error parameters were introduced leading to two major calibration values: (1) the local calibration values relating to either Persian Gulf (PGc) or Gulf of Oman (GOc); (2) the global calibration values over the entire computational domain (PGGOc). Considerably different model performance was appeared in the Persian Gulf (PG) compared to either the Gulf of Oman (GO) or entire computational domain (PGGO) when ST3 package was employed, while obtained results using ST6 package showed negligible sensitivity to the domain. During the time period the cyclone Phet has traversed across the study area, the model overestimated the wave height in comparison with altimeter dataset. Mean bias distribution over the study area indicates that calibrated ST6 outperforms calibrated ST3 over GO; however, both packages provide similar results over PG. Considering different methods for nonlinear interaction term led to similar directional wave spectrums over the study area and negligible changes in bulk wave parameters. In this study, the Gaussian Quadrature Method (GQM) method was implemented in the WAVEWATCH-III model and used along with embedded formulations for estimating the nonlinear wave interactions. The results of Discrete Interaction Approximation (DIA), Generalized Multiple Discrete Interaction Approximation (GMD), GQM and Webb-Resio-Tracy (WRT) methods were compared for ideal test cases. The GQM was in good agreement with the exact WRT method while its medium resolution conjuration was ~10 times faster than WRT. The GMD was more than 50 times faster than GQM but it could not reproduce WRT results for slanting fetch condition. Two different packages named ST3 and ST6, were employed for calculating the wind input and energy dissipation formulations over the Gulf of Mexico. The high quality ERA5 wind data from August to September in 2017 blended with Holland parametric model were used to run the wave model. The simulation period includes both fair weather condition and extreme events of Hurricanes Harvey and Irma. The performance of wave model using different nonlinear wave interaction terms was assessed against bulk wave parameters measured by in-situ buoys as well as altimeter-derived data by introducing a new error index. The general features of in-situ directional wave spectra were well captured by all DIA, GMD, GQM and WRT methods; however, the spectra produced by GMD and GQM were closer to the results by WRT method. Interestingly, the DIA method with calibrated whitecap dissipation term outperformed other methods in reproducing in-situ data (i.e. wave bulk parameters and wave spectra) during both fair weather and extreme events; indicating overfitting in the white capping or/and wind input terms in the wave model.

خليج فارس , درياي عمان , خليج مكزيك , طوفان فِت , طوفان هاروي , طوفان ايرما , روش جي كيو ام

persian gulf , Gulf Of Oman , gulf of mexico , Phet , Harvey , Irma , GQM

MosTafa Beiramzade

Dr. Siadat Moosavi