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Characteristics of the Marine Atmospheric Boundary Layer under the Influence of Ocean Surface Waves
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2022
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Source: Journal of Physical Oceanography, 52(6), 1261-1276
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Journal Title:Journal of Physical Oceanography
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Description:The deviation of the mean wind profile from Monin–Obukhov similarity theory (MOST) within the wave boundary layer (WBL) is investigated by combining four levels of turbulence data measured on a fixed platform with wave measurements. The data suggest that the mean wind profile follows MOST under wind-sea conditions because the turbulence statistics and structure are consistent with the attached eddy model. However, pronounced swell-related peaks appeared in the velocity spectra and uw cospectra under swell conditions. The upward wave-induced stress resulted in a large wind gradient within the WBL when light winds traveled with the swell, while the opposite result was found for the wind-opposite swell. These phenomena were analyzed based on the velocity spectra and turbulence variances. We found that the deviation of the wind profile was due to the longer or shorter length of the f −1 scaling region appearing in the velocity spectra. Significance Statement: The interactions between ocean waves and adjacent airflow affect the functioning of Earth’s climate and weather systems. However, our physical understanding of air–wave interactions remains incomplete, for example, the deviation of the mean wind profile from Monin–Obukhov similarity theory within the wave boundary layer. In this study, we aim to provide new insights by analyzing four-level turbulence data and wave measurements. We found that when the local wind travels faster than the wave, the airflow over the wavy surface is similar to that over land because the effects of waves do not reach the measurement heights. In conditions with wind-following or -opposing fast-propagating waves, the overlying airflow is greatly modified as the turbulence is affected by wave-induced perturbations.
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Source:Journal of Physical Oceanography, 52(6), 1261-1276
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