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In this study, the relation between rogue wave occurrence statistics and properties of the directional wind-wave spectrum is investigated. The study is conducted by means of the fully nonlinear phase-resolving numerical model and the high-order spectral model. Benjamin-Feir Index (BFI ), Π numbers and Modulation Index, which are designed to represent instabilities in nonlinear wave systems, are used as indicators for the occurrence of rogue waves. Rogue wave statistics and indicator parameters' performance are assessed based on numerical simulations and compared against in situ measurements. Directional Π 2 is found to be the best performing indicator. It is also observed that probability of rogue wave occurrence further peaks up at high directionality where modulational instability should be suppressed. It is argued that this condition is associated with the linear superposition of waves coming from different directions. Therefore, both directionality and instability, i.e. both linear and nonlinear effects, appear to be important physical mechanisms contributing to the extreme wave statistics. However, it is also argued that rogue wave occurrence is a transient (fast) event and cannot be accurately represented with conventional probability distribution functions. [ABSTRACT FROM AUTHOR]

Sea spray comprises liquid droplets that cover a broad range of radii, from 0.01 to 1000 μm. For field observations, it is difficult to measure the sea spray size distribution over the full range of radii, particularly as spray production is associated with extreme weather conditions. As a result, differences in magnitude of the sea spray production estimates reach 6 orders. In this study, the sea spray volume flux (SSVF) was measured by laser altimeters under Tropical Cyclone Olwyn in the Indian Ocean. The results show that the SSVF increases gradually with the wind speed and is approximately 2 orders of magnitude larger than the results of two laboratory experiments and existing sea spray generation functions. The SSVF is also influenced by the sea state. When the nondimensional significant wave height is factored in a new parameter R B u ∗ 2 / gH s 1 / 3 , the correlation coefficients are improved, increasing to 0.85 and 0.88. Finally, a new parameterization for SSVF generation function is proposed in terms of the nondimensional wave height and windsea Reynolds number RB. [ABSTRACT FROM AUTHOR]

In this study, we investigate how sea ice extent and thickness are affected by additional turbulent mixing from unbroken surface waves. This 'surface wave mixing' (SWM) is parameterized by the inclusion of an extra mixing term in the k-ε turbulence scheme implemented in a global-scale ocean model (MOM5). Relative to simulations without SWM, we observe a reduction of seasonal extremes of sea ice extent in the Antarctic of about 9%. This reduction brings the seasonal amplitude of sea ice extent significantly closer to observations, as well as causing an increase in sea ice thickness of up to 15 cm leading up to and during the Antarctic summer. [ABSTRACT FROM AUTHOR]

This paper presents an assessment of the impact of the ocean circulation on modeled wave fields in the Southern Ocean, where a systematic positive bias of the modeled wave height against altimetry data has been reported. The inclusion of ocean currents in the wave model considerably reduces the positive bias of the simulated wave height for high southern latitudes. The decrease of wave energy in the presence of currents is almost exclusively related to the reduction of the relative wind, caused by an overall co-flowing current field associated with the Antarctic Circumpolar Current. Improvements of the model results are also found for the peak period and the mean period against a long-term moored buoy. At the mooring location, the effect of currents is greater for larger and longer waves, suggesting remotely generated swells are more influenced by the currents than local waves. However, an additional qualitative analysis using high-resolution currents in a finer grid nested to the global coarser grid shows that typical resolution of global hydrodynamic reanalysis is not sufficient to resolve mesoscale eddies, and as a consequence, the simulation of mesoscale wave patterns can be compromised. The results are also discussed in terms of the accuracy of forcing fields. [ABSTRACT FROM AUTHOR]