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Abstract We examine the dependence of the penetration depth and fractional surface area (e.g., whitecap coverage) of bubble plumes generated by breaking surface waves on various wind and wave parameters over a wide range of sea state conditions in the North Pacific Ocean, including storms with sustained winds up to 22 m s−1and significant wave heights up to 10 m. Our observations include arrays of freely drifting SWIFT buoys together with shipboard systems, which enabled concurrent high‐resolution measurements of wind, waves, bubble plumes, and turbulence. We estimate bubble plume penetration depth from echograms extending to depths of more than 30 m in a surface‐following reference frame collected by downward‐looking echosounders integrated onboard the buoys. Our observations indicate that mean and maximum bubble plume penetration depths exceed 10 and 30 m beneath the surface during high winds, respectively, with plume residence times of many wave periods. They also establish strong correlations between bubble plume depths and wind speeds, spectral wave steepness, and whitecap coverage. Interestingly, we observe a robust linear correlation between plume depths, when scaled by the total significant wave height, and the inverse of wave age. However, scaled plume depths exhibit non‐monotonic variations with increasing wind speeds. Additionally, we explore the dependencies of the combined observations on various non‐dimensional predictors used for whitecap coverage estimation. This study provides the first field evidence of a direct relation between bubble plume penetration depth and whitecap coverage, suggesting that the volume of bubble plumes could be estimated by remote sensing.
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This content will become publicly available on May 1, 2027
Mapping Coastal Ocean Surface Winds with High-Frequency Radar: A Tomographic Approach
Abstract We present a method to achieve continuous observations of ocean surface winds over the coastal zone from coastal high-frequency radar (HFR) systems via a new, tomography-based approach. The method estimates winds over the ocean via the inversion of a linear system of equations relating the received first-order signal power, backscattered from wind-driven ocean surface waves to the wind stress along the path between the radar and the scattering patch. In this formulation, the method holistically considers the role of surface wind waves as both a reflector and an attenuator of the radar signal as it propagates. When applied to observations from an array of 16-MHz HFRs, the tomographic approach achieves high spatial resolution coverage over the full first-order domain of the HFRs, on par with returns for surface currents themselves, and RMS differences against in situ wind observations of 1.1–1.5 m s−1.
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- PAR ID:
- 10699120
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Atmospheric and Oceanic Technology
- Volume:
- 43
- Issue:
- 5
- ISSN:
- 0739-0572
- Page Range / eLocation ID:
- 637 to 654
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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