Collaborative Research: Mapping the kinematics and dynamics of tidal ocean currents with surface drifters

该项目涉及对周日和半日斜压潮汐进行量化和绘图，即海洋中的内波，是太阳和月球迫使正压潮汐损失能量的结果。这项工作将主要使用由全球漂流者方案（GDP）的表面漂流浮标轨迹提供的海洋近表面每小时海流的独特数据集。该方法是由潮汐能量学的分析，区分时间平均，或锁相，斜压潮汐和时间变量，或非锁相，斜压潮汐。GDP数据集既足够大，又足够准确，它应该允许定量评估两种类型的斜压潮汐，并专门测试理论模型的散射相位锁定潮汐到非相位锁定潮汐。此外，分析将允许映射-锁相和非锁相潮汐-耗散率系数及其相关的动力过程，这可以根据地理位置和环境条件而不同。这种测绘将提供急需的信息，以改进海洋环流模式中潮汐混合的真实性和物理参数化。这项工作将有助于在全球范围内测量普遍表现出潮汐频率能量振荡的上层洋流。改进对海洋表面流的预测将对从航运业到季节性气候预报员等利益攸关方产生社会影响。该项目还将促进以气候为主题的教育计划，包括夏令营，动手活动，并加强现有的学校实地考察programmes.Estimates的相位锁定潮汐目前可从卫星高度计数据的分析，这些估计导致斜压潮汐模型的创建，该项目将测试和扩展使用GDP数据。由于潮汐动力学包括波浪散射和波浪耗散，测试这些模型将限制这些过程在区域和全球尺度上的物理合理参数化范围。最后，将把国内生产总值数据与潮汐和中尺度分辨海洋全球环流模型的输出进行系统比较，这一工作将有助于验证模型模拟，并为理解国内生产总值观测和所用统计方法的潜在偏差提供有用的背景。该项目将产生有关潮流的新知识，以便更好地了解潮汐动力学及其在维持全球温盐海洋环流方面的作用。新的漂流数据集，将被用来调查斜压潮汐现象是足够大的和独特的（时间，空间和准确性明智的），以提供一个定量描述的潮汐特性。此外，将获得潮汐/非潮汐相互作用的定性和潜在的新评估，包括其季节性和较长时间的变化。一种新的分解的潮汐能预算，分离的过程主要影响相位锁定和非相位锁定的潮汐信号，提出了指导分析和解释的漂流观测，以及测高数据和数值模拟。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This project is concerned with quantifying and mapping diurnal and semi-diurnal baroclinic tides, that is, internal waves in the ocean that are the result of the loss of energy from the barotropic tides forced by the Sun and the Moon. This work will primarily use a unique dataset of oceanic near-surface hourly currents provided by the trajectories of surface drifting buoys from the Global Drifter Program (GDP). The approach is guided by an analysis of tidal energetics which distinguishes between time-mean, or phase-locked, baroclinic tides and time-variable, or non-phase-locked, baroclinic tides. The GDP dataset is both large enough and sufficiently accurate that it should permit quantitative assessment of both types of baroclinic tides, and specifically test theoretical models for the scattering of phase-locked tides into non-phase-locked tides. In addition, the analyses will permit the mapping---for both phase-locked and non-phase-locked tides---of dissipation rate coefficients and their associated dynamical processes, which can be distinct based on geographical locations and environmental conditions. Such mapping will provide much needed information for improving the realism and physical parameterization of tidal mixing in ocean general circulation models. The work will contribute to the goal of measuring on a global scale upper-ocean currents which ubiquitously exhibit energetic oscillations at tidal frequencies. Improved prediction of ocean surface currents will have societal impacts for stakeholders ranging from the shipping industry to seasonal climate forecasters. The project will also contribute to a climate-themed educational program including summer camps, hands-n activites, and enhancements to existing school field trip programs.Estimates of the phase-locked tides are presently available from the analysis of satellite altimeter data,and these estimates have led to the creation of baroclinic tide models, which this project will test and extend using the GDP data. As tidal dynamics includes both wave scattering and wave dissipation, testing these models will place constraints on the range of physically plausible parameterizations for these processes on regional and global scales. Finally, the GDP data shall be systematically compared with outputs of a tide and mesoscale-resolving ocean global circulation model, an exercise which will be useful for validating the model simulations as well as providing a useful context for understanding potential biases of the GDP observations and statistical methods applied. This project will generate new knowledge concerning tidal currents in order to better understand tidal dynamics and their role in the maintenance of the global thermohaline ocean circulation. The new drifter dataset that will be utilized to investigate baroclinic tidal phenomena is both large enough and unique (temporally, spatially and accuracy wise) to provide a quantitative description of tidal properties. In addition, qualitative and potentially new assessments of tidal/non-tidal interactions will be obtained, including their seasonal and longer temporal variability. A novel decomposition of the tidal energy budget, which separates processes primarily affecting phase-locked and non-phase-locked tidal signals, is proposed to guide the analysis and interpretation of the drifter observations, as well as altimetry data and numerical simulations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.