The Analysis of Sea Surface Imagery for Whitecap Kinematics
The Analysis of Sea Surface Imagery for Whitecap Kinematics
复制标题
Whitecap 运动学海面图像分析
DOI：
10.1175/2010jtecho744.1
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发表时间：
2011
影响因子：
2.2
通讯作者：
W. Melville
中科院分区：
文献类型：
--
作者：
J. Kleiss;W. Melville
对可见光海面图像进行了分析，以确定单位海面面积、单位航速增量的平均破碎峰长度分布，L(C)。L(C)分布提供了从波场到表层流的尺度相关的descriptionofwavebreakingthatisvaluableforunderstandingwaveenergydissipation，动量通量，以及气体和海盐气溶胶的海-气通量。实现了两种从视频图像中确定L(C)的独立处理技术。特别是，破碎事件的速度定义的重要性被认为是作为单个值、作为时间的函数、或作为垂直于破碎前沿的afunctionofspaceandtime.Thevelocitycanfurthermorebedefinedasthefulltranslationalvelocityorasthe速度。讨论了不同的速度定义、阈值灵敏度、观测分辨率对L(C)分布的影响，以及地表洋流和长波轨道velocityarepresented.Theappropriatenessandlimitationsofthecomparisonofthefirstmomentof L(C)对破碎率的影响。L(C)之前的两次现场观测给出了性质不同的结果：Melville和Matusov发现L(C)的指数形式，而Gemmrich等人。得到了一个在中速时达到峰值的函数，它比梅尔维尔和马图索夫的函数高一个数量级。通过采用以前研究中使用的破碎速度的定义，这两个结果都可以使用当前的数据集进行定性地再现。作者认为，目前对破碎速度的最优解释将破碎速度分解为空间和时间的函数，并认为速度与破碎峰值垂直。
Visible sea surface images are analyzed to determine the distribution of the average length of breaking crests per unit sea surface area per unit speed increment L(c). The L(c) distribution offers a scale-dependent descriptionofwavebreakingthatisvaluableforunderstandingwaveenergydissipation,momentumfluxfrom the wave field to the surface currents, and air‐sea fluxes of gas and sea salt aerosols. Two independent processing techniques for determining L(c) from video images are implemented. In particular, the importance of the definition of the velocity of a breaking event is considered, as a single value, as a function of time, or as afunctionofspaceandtime.Thevelocitycanfurthermorebedefinedasthefulltranslationalvelocityorasthe velocity normal to the breaking front. The L(c) distributions resulting from various definitions of velocity, sensitivity to thresholds, observational resolution, and the effect of surface currents and long wave orbital velocityarepresented.Theappropriatenessandlimitationsofthecomparisonofthefirstmomentof L(c)with the breaking rate are discussed. Two previous field observations of L(c) give qualitatively different results: Melville and Matusov found an exponential form for L(c), whereas Gemmrich et al. obtained a function that peaks at intermediate speeds and is up to an order of magnitude higher than that of Melville and Matusov. Both results can qualitatively be reproduced using the current dataset by employing the definitions of breaking velocity used in the previous studies. The authors argue that the current optimal interpretation of breaking speed resolves the breaking velocity as a function of both space and time and considers the velocity orthogonal to the breaking crest.