Sea spray can contribute significantly to the exchanges of heat and momentum across the air–sea interface. However, while critical, sea spray physics are typically not included in operational atmospheric and oceanic models due to large uncertainties in their parameterizations. In large part, this is because of the scarcity of in-situ sea spray observations which prevent rigorous validation of existing sea spray models. Moreover, while sea spray is critically produced through the fundamental interactions between wind and waves, traditionally, sea spray models are parameterized in terms of wind properties only. In this study, we present novel in-situ observations of sea spray derived from a laser altimeter through the adoption of the Beer–Lambert law. Observations of sea spray cover a broad range of wind and wave properties and are used to develop a wind–wave-dependent sea spray volume flux model. Improved performance of the model is observed when wave properties are included, in contrast to a parameterization based on wind properties alone. The novel in-situ sea spray observations and the predictive model derived here are consistent with the classic spray model in both trend and magnitude. Our model and novel observations provide opportunities to improve the prediction of air–sea fluxes in operational weather forecasting models.

Extreme marine weather enhances the production of sea spray droplets which, in turn, affect the air‐sea fluxes. Despite the ability of sea spray to modulate air‐sea interaction processes, it remains under‐represented in tropical cyclone (TC) forecasting modeling. In this study, impacts of sea spray on the atmospheric and oceanic environments of TC Olwyn are investigated. This is achieved by high‐resolution nested simulations using an air‐sea‐wave model coupled with a sea spray production model. We compared two different sea spray models: a wave‐Reynolds‐number‐dependent model, and a wave‐steepness‐dependent spray model. By including a sea spray model, the root mean square error in the simulated TC Olwyn 10 m wind and significant wave height are significantly reduced by up to 30% and 26%, respectively, in comparison to the baseline simulation without spray. This improvement is because sea spray decreases air‐sea heat fluxes at larger radii of TC, and increases air‐sea heat fluxes at smaller radii of TC. In contrast to the simulated results without sea spray, sea spray increases the air‐sea heat (sensible + latent) energy transfer and intensifies TC Olwyn. Sea spray also triggers stronger upper‐ocean mixing and strengthens the TC‐induced sea surface temperature cooling. Our results thus imply that sea spray critically impacts the atmosphere and ocean conditions during extreme marine weather and thus needs to be considered explicitly in TC forecasting modeling.

Waves critically modulate the air‐sea fluxes, and upper‐ocean thermodynamics in a Tropical Cyclone (TC) system. This study improves the modeling of TC intensification by incorporating non‐breaking wave‐induced turbulence and sea spray from breaking waves into an atmosphere‐ocean‐wave coupled model. Notably, wind forecast error decreased by around 10% prior to TCs' peak intensity. The positive feedback of sea spray along with compensatory negative feedback from non‐breaking waves, overall enhanced TCs' intensity. These breaking and non‐breaking wave‐coupled processes consistently cool sea surface temperature, resulting in improvement of the modeled SST. Observed improvements in full‐year TC cases ranging from Categories I to IV in this study suggest that an accurate characterization of ocean wave‐coupled processes is crucial for improving TCs' intensity forecasts and advancing our understanding of severe weather events in both, the atmosphere and ocean.

Spume, large-radius seawater droplets that are ejected from the ocean into the atmosphere, can exchange moisture and heat fluxes with the surrounding air. Under severe weather conditions, spume can substantially mediate air-sea fluxes through thermal effects and thus needs to be physically parameterized. While the impact made by spume on air-sea interactions has been considered in bulk turbulent air-sea algorithms, various hypotheses in current models have resulted in uncertainties remaining regarding the effect of spume on air-sea coupling. In this study, we extended a classic bulk turbulent air-sea algorithm with a “bag-breakup” physical scheme of spume generation parameterizations to include spume effects in a complicated numerical model. To investigate the impact of spume on air-sea coupling, we conducted numerical experiments in a simulation of Tropical Cyclone Narelle. We observed a significant improvement in the ability to model minimum central pressure and maximum sustained surface wind speed when including the bag-breakup spume scheme. In particular, the impact of the bag breakup–generated spume is observed in the intensity, structure, and size of the tropical cyclone system through the modulation of local wind speed (U10), wave height (Hs), and sea surface temperature.