Parameterization of the sea spray generation function with whitecap coverage
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Parameterization of the sea spray generation function with whitecap coverage Jian Shi1*, Wenjing Zhang1, Xueyan Zhang1, Jingdong Liu1, 2, Zhenyu Liu1 1 College of Meteorology and Oceanography, National University of Defense Technology, Nanjing 211101, China 2 Unit 91604 of the Chinese People’s Liberation Army, Longkou 265700, China
Received 21 March 2020; accepted 20 May 2020 © Chinese Society for Oceanography and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
Sea spray droplets are produced by waves breaking on the sea surface, and they vary the transfer of energy between the atmosphere and ocean. The sea spray generation function (SSGF) is generally considered as a function of the initial radius of the spray droplets and the wind speed. However, ocean waves always exist at the air-sea interface, so it is not reasonable to consider only the effect of sea surface winds while ignoring the effects of ocean waves. Whitecap coverage is an important characteristic parameter of breaking waves, and researchers believe that this parameter is related to both wave state and wind speed. In this paper, the SSGF is parameterized by the whitecap coverage, and a new SSGF describing different droplet radii is organically integrated based on the whitecap coverage parameter. Then, with the relationship between the whitecap coverage and wave state, the influence of ocean waves on the SSGF for different wave states was analyzed by using observational data in the laboratory. The results show that the new SSGF that considers wave effects can reasonably describe the droplet generation process under different wave state conditions. Key words: sea spray generation function, whitecap coverage, wave state Citation: Shi Jian, Zhang Wenjing, Zhang Xueyan, Liu Jingdong, Liu Zhenyu. 2020. Parameterization of the sea spray generation function with whitecap coverage. Acta Oceanologica Sinica, 39(8): 24–33, doi: 10.1007/s13131-020-1618-9
1 Introduction Ocean waves are produced by the ocean winds. As the wind speed increases, the waves break, and tiny spray droplets leave the waves. The existence of sea spray droplets changes and influences the energy transfer between atmosphere and ocean. Furthermore, it affects the prediction of typhoon intensity and climate change which are closely related to the ocean (Liu et al., 2011; Wu et al., 2015; Rizza et al., 2018; Barthel et al., 2019). Sea spray droplets can be divided into two types: one is produced by the collapse of the bubble, and the other is mainly produced by the wind blowing against the wave crest (Veron, 2015). Breaking waves produce many bubbles in the sea, and when a bubble rises to the sea surface, it bursts and produces hundreds of film droplets. After the bubbles burst, a collapsing cavity is filled with surrounding water, then, the water rebounds rapidly as a column, and jet droplets are formed. The radius of bubble-induced film droplets and jet droplets ranges from 3−20 μm. Wind tears the wave crest and carries the droplets away, or the crest of a breaking wave c
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