Upper ocean physics: observations and applications

上层海洋的中尺度(~100公里)和亚中尺度(~1-10公里)过程在示踪剂的垂直输送、与大气交换热量和气体以及将营养物质从海洋内部提供到阳光照亮的真光带中起着基本作用。然而，从现场观测中估计造成这种传输的垂直速度将需要以令人望而却步的水平分辨率垂直采样海洋。在过去的5年里，已经发展了一种仅利用地面观测来诊断垂直速度的新方法，同时考虑了混合层的关键物理过程，并通过理想化和现实的数值模拟进行了检验。*拟议研究计划的长期目标是结合高分辨率卫星*对海面高度、温度和盐度的观测，以及由漂流提供的层结的现场观测，以估计：i)上层海洋示踪剂的水平和垂直湍流通量，以及ii)大、中、亚中尺度之间的动能转移。为了实现这一目标，未来5年将追求下列短期目标：*1)进一步开发和测试根据地面观测诊断垂直速度的新方法；*2)开发过滤与卫星高度计观测的内波有关的信号的方法；*3)利用高频雷达观测估计中、亚中尺度之间的动能转移*以调查低频海洋过程与高频海洋过程的相对重要性。*拟议的研究活动将为充分利用将于2021年提供的表层水海洋地形(SWOT)卫星高度计的高分辨率数据开辟新的视角。预期成果是对10-100公里范围内的上层海洋湍流示踪剂通量和动能转移的全球观测估计。这些观测估计反过来将提供有价值的基准，以调整和完善用于预测气候变化的全球海洋环流模型中未解决的过程的参数。

Mesoscale (~100 km) and submesoscale (~1-10 km) processes in the upper ocean play a fundamental role in the vertical transport of tracers, exchanging heat and gases with the atmosphere, and supplying nutrients from the ocean's interior into the sun-lit euphotic zone. However, estimating the vertical velocities responsible for this transport from in-situ observations would require to sample the ocean vertically at a prohibitive horizontal resolution. A new method to diagnose vertical velocities using only surface observations, while taking into account the key physical processes of the mixed layer, has been developed and tested against idealized and realistic numerical simulations during the past 5 years.***The long-term objective of the proposed research program is to combine high-resolution satellite***observations of sea surface height, temperature and salinity, and in-situ observations of stratification provided by drifting floats, to estimate: i) the horizontal and vertical turbulent fluxes of tracers in the upper ocean, and ii) kinetic energy transfers between large-, meso- and submeso-scales. To attain this objective, the following short-term objectives will be pursued in the next 5 years:***1) Further develop and test the new method to diagnose vertical velocities from surface observations;***2) Develop methods to filter signals associated with internal waves from satellite altimeter observations;***3) Estimate kinetic energy transfers between meso- and submeso-scales using high-frequency radar***observations to investigate the relative importance of low-frequency versus high-frequency oceanic processes.***The proposed research activities will open new perspectives to fully exploit the high-resolution data from the Surface Water Ocean Topography (SWOT) satellite altimeter that will become available in 2021. Expected outcomes are global observational estimates of upper ocean turbulent tracers fluxes and kinetic energy transfers in the range of 10-100 km. These observational estimates will in turn provide valuable benchmarks to tune and refine parameterizations of unresolved processes in global ocean circulation models used to predict climate change.