Air-Sea Exchange in the Southern Ocean

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。在南大洋，海气通量在改变海洋表面的水方面发挥着关键作用。它们决定了当水被表面埃克曼流作为纬向翻转环流的一部分向北输送时，水的性质如何变化。它们还确定了从南极绕极流北方侧翼下降到中等深度的中间和模式沃茨的特性，这些水域携带着它们与大气接触的指纹。数值天气预报模式或对卫星和现场数据的详细分析提供了一些网格化的海气通量产品。这些产品的差异很大，通常为50瓦/平方米或更大的时间平均值。此外，现有的通量产品是不够准确的，以充分解释所观察到的季节到年际变化的混合层热含量。此外，虽然海气通量被认为是在小的空间尺度上变化与中尺度海洋功能，如锋或涡，小尺度的变化通常是不解决海气通量products.Intellectual优点：本研究项目将调查混合层热收支和水团的转换在南大洋。这项工作的前提假设是，改进海气通量估计是增进对南大洋混合层过程了解的一个重要步骤。热量和淡水通量估计数将用于评价三个关键想法：（a）南大洋的地表水质量变化主要可以通过海气热量和淡水通量来解释，而不需要援引任何地下过程。(b)海洋上层的热量平衡应该关闭，无论是在区域范围内还是在系统范围内。海洋上层温度的季节到年际变化在很大程度上可以用海气热通量来解释，其中水平平流过程占了大部分差异。(c)小空间尺度，快速变化的表面通量是显着的，造成了很大的海气热量和淡水通量现有的不确定性，解决这些小尺度通量将减少上层海洋热量收支的不确定性。从本质上讲，这三个假设转化为一个概念，即改善我们对热通量的估计应该提高我们对南大洋发生的气候尺度过程的物理理解。将通过考虑海气通量性能的两个指标来评估南大洋尺度上重要的过程：随时间演变的混合层热收支的闭合和由海气通量驱动的向北Ekman平流和水团转换之间的时间平均平衡。将对一套现有的通量产品进行评价，并将通过测试可能的参数来开发一种新的混合通量估计，以找到一套最佳的卫星和数值天气预报产品，用于计算海气通量的批量算法。Braoder影响：该项目将提供部分支助，以便在海气交换这一重要领域培训一名博士后研究员。作为这项研究的一部分得出的南大洋海气热量和淡水通量估计数将通过一个网站公布。研究结果将有助于为今后在海气通量及其在气候中的作用方面取得进展奠定基础。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).In the Southern Ocean, air-sea fluxes play a critical role in transforming water at the ocean surface. They determine how water properties change when water is carried northward by surface Ekman currents as part of the meridional overturning circulation. They also determine the properties of Intermediate and Mode Waters that descend to mid-depth from the northern flank of the Antarctic Circumpolar Current, carrying with them fingerprints of their contact with the atmosphere. A number of gridded air-sea flux products are available from numerical weather prediction (NWP) models or detailed analyses of satellite and in situ data. These products differ substantially, often by 50 Watts per square meter or more in the time-averaged mean. In addition, the existing flux products are not accurate enough to explain fully the observed seasonal to interannual variations in the mixed-layer heat content. Moreover, while air-sea fluxes are thought to vary over small spatial scales associated with mesoscale ocean features such as fronts or eddies, small-scale variations are typically not resolved in air-sea flux products.Intellectual Merit: This research project will investigate the mixed-layer heat budget and water mass transformation in the Southern Ocean. The work is predicated on the hypothesis that improving air-sea flux estimates is an essential step towards an improved understanding of Southern Ocean mixed-layer processes. Heat and freshwater flux estimates will be used to evaluate three key ideas: (a) Surface water mass transformation in the Southern Ocean can be explained primarily through air-sea heat and freshwater fluxes, without requiring that any subsurface processes be invoked. (b) The upper ocean heat balance should close, both regionally and on a system-wide scale. Seasonal to interannual variations in upper ocean temperature should be explainable largely by air-sea heat fluxes, with horizontal advective processes making up most of the difference. (c) Small-spatial scale, rapid variations in surface fluxes are significant, contributing much of the existing uncertainty in air-sea heat and freshwater fluxes, and resolving these small-scale fluxes will reduce the uncertainties in upper ocean heat budgets. In essence, these three hypotheses translate into a single concept, that improving our estimates of heat fluxes should improve our physical understanding of the climate-scale processes that occur in the Southern Ocean. Processes that matter on the scale of the Southern Ocean will be evaluated by considering two metrics of air-sea flux performance: the closure of a time-evolving mixed-layer heat budget and time-averaged balance between northward Ekman advection and water mass conversion driven by air-sea fluxes. A suite of existing flux products will be evaluated, and a new, hybrid flux estimate will be developed by testing possible parameters to find an optimal set of satellite and numerical weather prediction products to feed into the bulk algorithms used to compute air-sea fluxes. On a regional scale, shipboard meteorological data will be used to assess the small-scale structure of air-sea fluxes.Braoder Impacts: The project will provide partial support in order to train one postdoctoral researcher in the important area of air-sea exchange. Estimates of Southern Ocean air-sea heat and freshwater fluxes derived as part of this research will be released via a website. Research findings will help to lay the groundwork for future advances in air-sea fluxes and their role in climate.