Upper ocean physics: observations and applications

上层海洋的中尺度（~100 km）和亚中尺度（~1 ~10 km）过程在示踪剂的垂直输送、与大气交换热量和气体以及将海洋内部的营养物质输送到阳光照射的光区中起着重要作用。然而，从现场观测估计造成这种输送的垂直速度需要以高得令人望而却步的水平分辨率对海洋进行垂直采样。在过去的5年中，研究人员开发了一种仅利用地面观测资料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测试。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，以及漂流浮标提供的分层现场观测，以估计：i)上层海洋中示踪剂的水平和垂直湍流通量，以及ii)大、中尺度和亚中尺度之间的动能转移。为实现这一目标，今后5年将努力实现以下短期目标：***1)进一步发展和试验利用地面观测资料诊断垂直速度的新方法；***2)发展从卫星高度计观测中过滤与内波有关的信号的方法；***3)利用高频雷达观测估计中尺度和亚中尺度之间的动能转移，以研究低频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年可用的地表水海洋地形（SWOT）卫星高度计的高分辨率数据开辟新的视角。预期结果是在10-100公里范围内对海洋上层湍流示踪剂通量和动能转移的全球观测估计。这些观测估计将反过来为调整和改进用于预测气候变化的全球海洋环流模式中未解决过程的参数化提供有价值的基准。

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.