Spectral Energy Dissipation in Broad-banded Wave Fields

该团队在之前NSF资助的研究中，在远程估计开放海洋中波浪破碎的能量耗散方面取得了重大进展，在该研究中，他们验证了在没有涌浪的情况下对风浪破碎的远程观测。该项目将把研究扩展到宽带波场（即，混合海洋）。具体目标是：1.利用宽带波场中的同步现场观测，从菲利普斯（1985）分布中得到的能量耗散，2.确定能量耗散对波龄和频率方向传播的依赖性，以及3。测试常用的平衡近似的有效性，其中能量耗散由风输入平衡。将进行两个现场实验，通过同时进行的远程和现场观测来估计波浪破碎期间的能量耗散。这些实验将从最近对华盛顿湖和普吉特湾窄带破碎波中能量耗散的观察中逐步扩展（Thomson等人，2009年）。第一个实验将在胡安·德富卡海峡进行，第二个实验将在北太平洋进行。基于傅立叶的方法（Thomson和杰瑟普，2009年）在窄带波的远程观测中表现良好，将适用于宽带波。一个结构函数方法（Gemmrich，2009）开发的固定多普勒剖面的原位速度将适用于观测从一个新的自由漂移platform.Intellectual MeritQuantification的能量耗散波破碎过程中是必不可少的精确建模的波浪和海洋状态的演变。拟议的研究将继续测试和应用一个假设，利用波峰的分布来远程估计耗散[菲利普斯，1985]。远程估计是光谱的，因此理想的输入到数值模型，但是估计需要确定一个无标度的破缺参数B。最近已经验证了菲利普斯公式，包括窄带波场的B的确定（Thomson等人，2009年），但不是宽带波场是典型的开放海洋条件。拟议的研究将扩大验证，同时评估频率方向传播，波龄，风应力的依赖性打破。更广泛的影响拟议的研究将包括博士生，谁将参与工作的各个方面的培训。拟议的研究将纳入正在进行的外联活动，包括在华盛顿周末（华盛顿大学开放日）和KCTS公共电视台的演示？科学咖啡馆。拟议研究的结果将在会议和同行评审期刊上发表。这些结果的潜在应用包括改进的全球波浪模型，用于气候预测和航运/海军行动。

This team has made significant progress toward remotely estimating energy dissipation by wave breaking in the open ocean in a previous NSF-funded study in which they validated remote observations of wind-wave breaking in the absence of swell. This project will extend that research to broad-banded wave fields (i.e., mixed seas). The specific objectives are to:1. Validate energy dissipation from the Phillips (1985) distribution using simultaneous in situ observations in broad-banded wave fields,2. Determine the dependence of energy dissipation on wave age and frequency-directional spread, and3. Test the validity of a commonly used equilibrium approximation, in which energy dissipation is balanced by wind input.Two field experiments will be conducted to estimate energy dissipation during wave breaking via simultaneous remote and in situ observations. The experiments will extend incrementally from recent observations of energy dissipation in narrow-banded breaking waves on Lake Washington and Puget Sound (Thomson et al., 2009). The first experiment will be in the Juan de Fuca Strait, and the second experiment will be in the North Pacific. A Fourier based method (Thomson and Jessup, 2009) that has performed well for remote observations of narrow-banded waves will be adapted to broad-banded waves. A structure function method (Gemmrich, 2009) developed for stationary Doppler profiles of in situ velocity will be adapted to observations from a new free drifting platform.Intellectual MeritQuantification of energy dissipation during wave breaking is essential for accurate modeling of waves and the evolution of sea states. The proposed research will continue testing and application of a hypothesis for remotely estimating dissipation using the distribution of wave crests [Phillips, 1985]. The remote estimates are spectral, and thus ideal as input to numerical models, however the estimates require determination of a scale-free breaking parameter b. The Phillips formulation recently has been validated, including determination of b, for narrow-banded wave fields (Thomson et al., 2009), but not for the broad-banded wave fields that are typical of open ocean conditions. The proposed research will expand the validation, while evaluating the dependence of breaking on frequency-directional spreading, wave age, and wind stress.Broader ImpactsThe proposed research will include training of a PhD student, who will participate in all aspects of the work. The proposed research will be incorporated into ongoing outreach activities, including demonstrations during Washington Weekend (University of Washington open house) and presentations at KCTS public television?s Science Café. Results from the proposed research will be presented at conferences and in peer-reviewed journals. Potential applications of the results include improved global wave models for climate predictions and shipping/naval operations.