Characteristics of whitecaps estimated from image processing of the ocean surface

Yukun Wang, Ryo Ohnishi, Yuji Sugihara, Yoshihiro Nakamura, Osama Eljamal

Research output: Contribution to conferencePaperpeer-review

Abstract

Whitecaps generated by wave breaking on the ocean surface play an important role in the local interaction between the atmosphere and the ocean. Whitecap coverage is defined by the area of whitecaps per the unit ocean surface. It has been recognized as one of important physical quantities for describing the ocean surface fluxes such as the momentum, heat and carbon dioxide, so that the quantitative evaluation of whitecap coverage becomes significant from viewpoints of environmental hydraulics and ocean engineering. In this study, in order to validate typical estimation methods for whitecap coverage, the AWE algorithm proposed by Callaghan and White (2008) was compared with the threshold method adopted usually in previous studies. The agreement between both was examined on the basis of the influence of solar radiation. Previous studies have suggested that the depth of bubble penetration generated by wave breaking may be proportional to the significant wave height. Based on this assumption, we proposed a new index for expressing characteristics of whitecaps, i.e., whitecap depth, indicating the product of whitecap coverage and the bubble penetration depth. This quantity denotes the averaged depth of the bubbly layer per the unit ocean area, and can be expected to become a more significant quantity than whitecap coverage. In addition, for the data of whitecap coverage obtained from the AWE method, we investigated the relation of whitecap depth with 10-m wind speed or the windsea Reynolds number.

Original languageEnglish
Publication statusPublished - 2020
Event22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Creating Resilience to Water-Related Challenges, IAHR-APD 2020 - Sapporo, Virtual, Japan
Duration: Sep 14 2020Sep 17 2020

Conference

Conference22nd Congress of the International Association for Hydro-Environment Engineering and Research-Asia Pacific Division: Creating Resilience to Water-Related Challenges, IAHR-APD 2020
Country/TerritoryJapan
CitySapporo, Virtual
Period9/14/209/17/20

All Science Journal Classification (ASJC) codes

  • Ecology
  • Environmental Engineering

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