Session: 02-04-02 Probabilistic and Spectral Wave Modelling (Co-hosted with the Ian Young Honoring Symposium)

Paper Number: 104355

104355 - Sea Spray Production During Extreme Marine Weather Conditions: Observations During Tropical Cyclones Olwyn and Veronica 

During extreme weather conditions, the wind can tear off droplets from the wave crests to produce sea spray. These airborne droplets can then modulate the fluxes of heat and momentum, leading to changes in tropical cyclone intensity. Measuring and predicting the volume of sea spray produced at the ocean surface is thus critical for accurate forecasts of extreme weather events. Unfortunately, reliable observations of sea spray in the field are extremely rare. For this reason, most parameterizations of sea spray volume are either derived from or validated using laboratory experiments. While these laboratory experiments have significantly improved our understanding of sea spray dynamics and production, the wave conditions in these laboratory experiments are nearly two orders of magnitude smaller than in the field, meaning we are strongly relying on the extrapolation thereof to field conditions. Not surprisingly, differences between contemporary sea spray models is currently multiple orders of magnitude.

In this study, we use laser altimeter observations obtained at a fixed observational platform located on the north shelf of Western Australia to obtain rare estimates of the sea spray flux in the field. We do so for two tropical cyclones (TCs), TC Olwyn and TC Veronica, which passed the observational site in 2015 and 2019, respectively. These extreme weather events led to maximum wind speed and significant wave height at the platform of 22 m/s and 7 m, respectively, for TC Olwyn, and 29 m/s and 8 m, respectively, for TC Veronica. We observe that the estimated sea spray volume flux matches surprisingly well with the classical model of Andreas (1992). We also observe a tentative flattening of the sea spray volume flux around 30 m/s, although the size of our dataset is too small to confirm such a change in trend.

Presenting Author: Joey Voermans University of Melbourne

Presenting Author Biography: Dr. Joey Voermans is an expert in experimental fluid mechanics, and has expertise in topics including waves, the air-sea-wave-ice coupled system, turbulence and sediment transport. Dr. Joey Voermans has extensive experience in the design, execution and analysis of laboratory and field experiments.

Authors:

Joey Voermans University of Melbourne
Xingkun Xu University of Melbourne
Alexander Babanin University of Melbourne