| 摘要: |
| 通过对国内外白浪研究和应用的分析，首次提出了有效白浪寿命的定义，给出了计算白浪寿命的公式及测量方法和结果，并报告了以此方法在渤海实测的结果，得到了白浪寿命TL海面风速U10的关系为：TL=0.26U10以及白浪寿命概率分布近于瑞和分布等。 |
| 关键词: 白浪 白浪寿命 现场测量 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金资助项目，49376254,19332010号 |
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| DEFINITION AND MEASUREMENT OF OCEANIC WHITECAP LIFETIME |
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LOU Shun-li,CAO Lu-jie,TIAN Ji-wei
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Physical Oceanography
Laboratory, Ocean University of Qingdao, Qingdao, 266003
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| Abstract: |
| Oceanic whitecaps, resulting from wave breaking play an important role in affecting air-sea fluxes and marine remote sensing. So far, measurements of whitecap have been limited to establishing the relationship between whitecap coverage and wind speed. In present study, the authors proposed a definition of average whitecap lifetime and the method of its measurement in time and space for the first time, and also presented the method for calculating the whitecap lifetime TL, for comparison with results from actual measurements in the Bohai Sea. Oct. 31 to Nov. 7, 1989 observations were conducted from a platform at 39o09'N, 119o42'E in the Bohai Sea. The observer followed 20 whitecaps for roughly 30 min intervals at certain in the studied sea area to measure their 20 lifetimes and defined their average as significant whitecap lifetime. The field experiment, during which wind speeds were 3 to 18.5 m/s, yielded 2 data sets.
This study showed that whitecap lifetime, TL, increases linearly with wind speed U10, according to the relationship, TL=0.26U10, while foam lifetime varies with wind velocity (with the separating point at 7 m/s), and increases sharply at roughly U10= 7 m/s, maximizing at about U10 = 15 m/s, and then decreases with wind velocity. The foam lifetime TLF = 23 s when wind velocity U10 > 7 m/s and = 50s when U10 > 7 m/s. It is noteworthy that the abrupt increase of foam lifetime at about U10 = 7 m/s as shown in Figure 2b is consistent with the variation of the characteristic length of bubble vertical entrainments pointed out by Wu (1988). The possible explanation is that the foam consists of bubbles and hence its behavior has close relation with the bubble.
The whitecap lifetime follows Rayleigh distribution, the results of a simple empirical algorithm based on wave breaking probability and whitecap lifetime to calculate whitecap coverage were compared with Wang (1990)'s results obtained in the same place. |
| Key words: Whitecap, Whitecap lifetime, Actual measurement |
