The Equatorial Mixed Layer and Upper Ocean Mixing

热带混合层的日循环是控制海气热湿交换的动力学的核心，而海气热湿交换又是各种赤道现象的核心，包括热带不稳定波、马登-朱利安涛动、厄尔尼诺/南方涛动、热带风暴气旋生成和季风季节的总体循环。季节性混合层以下的增强分层也很重要，因为它调节从较冷的，营养丰富的上升流沃茨下面的表层垂直通量。了解控制湍流混合的动量和示踪剂在这个过渡层的过程是一个突出的问题，在上层海洋物理。基于模拟结果和先前的观测，该项目的研究人员将追求这样的假设，即活跃混合层中的湍流结构与上密度跃层的剪切相结合，产生能量充沛的近N内波（NNIW）。这些NNIW仅限于最上层密度跃层中浮力频率升高的区域。当它们破裂时，它们有助于穿过过渡区的湍流耗散和混合。在热带地区，这种NNIW生成最有可能的候选者是夜间浮力驱动的对流与赤道暗流切变相结合。热带一代的NNIW将与以前的温度-纬度观测的朗缪尔环流和惯性流的类似一代进行比较，使用高分辨率相控阵多普勒声纳，快速剖面CTD和R/V Revelle上的高分辨率声学多普勒系统的组合进行的新观测。该项目的重点是空气/海洋系统中至关重要但尚未完全了解的一个环节：海洋最上层的净混合。混合层和最上层的密度跃层一起形成大气和深海之间的重要屏障，控制着热量、动量、营养物质和温室气体的净通量。最上层对海洋生物也至关重要，它是光线和营养物质相遇的地方，也是污染物和污染物分散的地方。这些通量的适当缩放已被证明是重要的全球海气耦合模拟，这可能是敏感的表面混合的程度和混合层的深度。更广泛的影响。这些结果将有助于改进海气交换估计，从而改进环境和气候影响，从而有助于改进作出长期政策决定所依据的信息。结果和解释将广泛传播，以提高科学认识，促进决策和进一步的科学工作。拟议的活动将为研究生提供培训和科学机会，并为正在进行的涉及学生、博士后和暑期实习生的科学研究提供数据支持。将积极发展各机构之间的伙伴关系和协作。

Diurnal cycling of the tropical mixed layer is central in the dynamics governing air-sea exchanges of heat and moisture which, in turn, are central to a variety of equatorial phenomena including Tropical Instability Waves, the Madden-Julian Oscillation, El Nino/Southern Oscillation, tropical storm cyclogenesis, and the overarching cycle of monsoon seasons. The enhanced stratification below the seasonal mixed layer is also important, as it regulates vertical fluxes into the surface layer from the cooler, nutrient rich upwelling waters below.Understanding the processes that control turbulent mixing of momentum and tracers in this transition layer is an outstanding problem in upper-ocean physics. Based on both modeling results and prior observations, this project's investigators will pursue the hypothesis that turbulent structures in an active mixed layer, combined with shear across the upper pycnocline, generate energetic Near-N Internal Waves (NNIW). These NNIW are confined to the region of elevated buoyancy frequency in the uppermost pycnocline. When they break, they contribute to turbulent dissipation and mixing across the transition zone. In the tropics, the most likely candidate for this kind of NNIW generation is nighttime buoyancy-driven convection combined with the Equatorial Undercurrent shear. The tropical generation of NNIW will compared with previous temperate-latitude observations of the analogous generation by Langmuir circulation and inertial currents, using new observations taken with a combination of a High-resolution Phased Array Doppler sonar, the fast-profiling CTD, and the High-resolution Acoustic Doppler systems aboard the R/V Revelle.Intellectual merit. The project focuses on a link in the air/ocean system that is vitally important yet incompletely understood: net mixing through the uppermost layers of the sea. The mixed layer and uppermost pycnocline together form a crucial barrier between the atmosphere and deep ocean, controlling the net fluxes of heat, momentum, nutrients, and greenhouse gases. This uppermost layer is also vital to marine life, setting the scene where light and nutrients meet, and where pollutants and contaminants are dispersed. Appropriate scaling of these fluxes has been shown to be important to global air-sea coupled simulations, which can be sensitive to both the degree of surface mixing and to the mixed layer depth. Broader impacts. The results will help improve air-sea exchange estimates, and hence both environmental and climate effects, thereby helping improve the information by which long-term policy decisions are made. The results and interpretations will be disseminated broadly to enhance scientific understanding and facilitate both decision making and further scientific work.The proposed activity will provide training and scientific opportunities for a graduate student, and data to support ongoing scientific studies involving students, post-docs, and summer interns. Partnerships and collaborations across institutions will be actively developed.