Collaborative Research: A Two-Stage Towing System for Swath-Mapping Ocean Turbulence

P.I.Gargett，Ann(Old Dominion University)提案#：0220504合作机构：Woolsey，Craig(VA Tech.)建议#：0220745私人投资促进机构建议建造一个双体拖曳系统，以建立一个稳定的海洋湍流测量平台。这项工作建立在一种有效的湍流测量工具的潜力之上，该工具使用非标准方式的声学多普勒电流测量。特别值得一提的是，在海洋中水平移动五光束VADCP可以产生垂直平面的“条带图”，其中包括关键的湍流量，如垂直动量应力、湍动能及其耗散率，以及平均流及其垂直切变的标准测量结果。这些测量需要一个足够稳定的平台，就像这里建议的那样。从原型拖曳系统进行的初步海上测量表明，两级设计可以提供所需的稳定性。这项初步试验还阐明了在近海环境中持续测绘所需的设计修改：为(I)一次拖体和二次拖体之间的电缆长度和(Ii)二次拖体的平均姿态提供船上控制。具体地说，私人投资促进机构建议设计必要的控制系统，建造一个完整的拖曳系统，以便在200米深处作业，并进行沿海近海试验巡航，以记录该系统的运动特征，并使用1.2兆赫5波束VADCP收集初步数据，该系统可在上下两种模式下部署。在这项浅水系统的工作过程中，他们还将探索在后续系统中实现电缆长度调整的各种选择，以便在整个海洋深度上运行。如果成功，这一进展将对湍流研究以外其他领域的上层海洋观测能力产生广泛影响，从而能够对生物薄层和主导海洋与大气之间气体传输的近地表气泡云等特征进行空间测绘。

P.I. Gargett, Ann (Old Dominion University) Proposal #: 0220504Collaborating Inst: Woolsey, Craig (VA Tech.) Proposal #: 0220745 The PIs propose to construct a two-body towing system to create a stable measurement platform for ocean turbulence measurements. This work builds on the potential for an effective turbulence survey tool using acoustic Doppler current measurements in non-standard ways. In particular, horizontally moving a 5-beam VADCP through the ocean can produce vertical-plane "swath-maps" of crucial turbulence quantities such as vertical momentum stresses, turbulent kinetic energy, and its dissipation rate, as well as standard measurements of mean currents and their vertical shear. These measurements require a sufficiently stable platform, as proposed here. Preliminary offshore measurements taken from a prototype towing system suggest that a two-stage design can provide the required stability. This preliminary testing also clarified the design modifications needed for continuous mapping in offshore environments: provision of shipboard controls for (i) the length of cable between primary and secondary tow bodies and (ii) mean attitude of the secondary tow body. Specifically, the PIs propose to design the necessary control systems, build a complete towing system for operation to depths of 200m, and carry out a coastal offshore test cruise to document the motion characteristics of the system and collect preliminary data with a 1.2MHz 5-beam VADCP, deployed in both upward and downward looking modes. During the course of this work with a shallow system, they will also explore options for accomplishing cable length adjustments in a subsequent system to operate over full ocean depths. If successful, this development would have broad impacts on upper ocean observational capabilities in areas other than turbulence research, enabling spatial mapping of such features as biological thin layers and the near-surface bubble clouds that dominate gas transfer between ocean and atmosphere.