ST6: Observation-Based Physics

in the Third-Generation Wave Forecast Models WAVEWATCH-III, SWAN, WWM-III and WAM

and

Modelling and Predicting Tropical Cyclone Intensity

Wave-Coupled Impacts on both Sides of the Ocean Interface

Alexander V. Babanin (University of Melbourne)

Time:

2:30PM Thursday, 26 November 2025

Location:

Science East, Room E0.32

The seminar will present research on two Metocean topics, which started as academic studies and led to significant advances of forecast models: for wind-generated waves and for tropical cyclones, respectively.

Major update of the physics of the third-generation models, known as ST6 package (in WW3) will be reported. The new source terms for wind input, whitecapping dissipation, interaction of waves with adverse winds (negative input), swell attenuation, nonlinear interactions and wave-ice interactions have been developed and implemented in WAVEWATCH-III, SWAN, WWM-III and WAM models, including their operational versions. Physics and parameterisations for the new source functions are based on observations, which allowed us to reveal features and processes previously unknown and not accounted for. For extreme conditions, physics of the wind input and whitecapping dissipation terms exhibit additional features irrelevant or inactive at moderate weather. In order to test the source functions independently, and control the flux balance in the model, additional observation-based constraints are implemented. At each time step, the total momentum input is verified to match an independently known wind stress. The new versions of the models have undergone extensive testing by means of academic tests, regional and global wave hindcast, modelling extreme conditions ranging from tropical cyclones to the marginal ice zone.

Tropical cyclones is the second topic of the presentation. While prediction of TC track has improved significantly over the two decades, forecast of their intensity has not. Apparently, some physics is missing in their understanding and description. In this presentation, we will discuss wave-coupled contributions to the Metocean processes on both sides of the ocean interface during tropical cyclones. On the atmospheric side this relates to the production of spray and its impacts on the heat fluxes. On the ocean side these effects are due to wave mixing which affects heat content of the upper ocean. Thus, we will report improvements of the modelling of TC intensification by incorporating turbulence induced by the wave orbital motion and sea spray from breaking waves into an atmosphere-ocean-wave coupled model. In particular, wind forecast error decreased by around 10% prior to TCs' peak intensity in full-year TC hindcast for the North-Western shelf of Australia, with Cyclones ranging from Categories I to IV.

Bio

Alexander V. Babanin is Professor in Ocean Engineering and Director of the Centre for Disaster Management and Public Safety at the University of Melbourne, Australia. Qualifications: BSc (Physics), MSc (Physical Oceanography) (Lomonosov Moscow State University, Russia), PhD (Physical Oceanography) (Marine Hydrophysical Institute, Sevastopol, Russia). Worked as a Research Scientist in the Marine Hydrophysical Institute, as an academic in the University of New South Wales, ADFA, Canberra; University of Adelaide, South Australia; Swinburne University of Technology, Melbourne. Areas of expertise, research and teaching, are wind-generated waves, maritime, coastal and Arctic engineering, air-sea interactions, ocean turbulence and ocean dynamics, climate, environmental instrumentation and remote sensing of the ocean. These include extreme Metocean conditions, from tropical cyclones to Arctic and Antarctic environments. 430+ career total publications.