Structure and transport properties of jets in the atmosphere and oceans

在过去的几年里，大气和海洋混合在不同情况下的强烈不均匀性已经变得越来越明显，因为高分辨率数值模拟和观测开始准确地表示空气和水团及其成分的详细空间结构。混合现在被认为是局限于不同的纬度地区，往往由尖锐的梯度，表明动态传输障碍。在大气层中由波和涡引起的不均匀混合与纬向排列的喷流的存在有着内在的联系，喷流不仅是涡混合的结果，而且也是在不同纬度区域组织混合的结果。这种组合效应是一种动态反馈，现在已知它在非常一般的条件下起作用。非均匀混合对于诸如水蒸气、二氧化碳、臭氧、热量和盐度等成分的输送非常重要;它们的非均匀再分布影响着全球辐射平衡和区域气候变化。尽管最近取得了一些进展，但对带状急流组织非均匀混合的方式，特别是这种混合的垂直结构的完整理解仍然是难以捉摸的。近年来，人们对喷流和混合的水平结构的理解取得了进展，特别是对位涡的理解，位涡是一个包含水平旋转运动和密度分层信息的关键动力学量。这个项目的目的是建立在最近的工作，以发展一个完整的理论，垂直结构的射流和混合。在这样做的过程中，它将有助于我们理解大气和海洋中占主导地位的喷流结构的结构，并预测它们如何在不同的强迫条件下达到动力学平衡，这些条件可能会随着气候的变化而变化。预计新理论将使我们能够评估气候模型预测的可靠性，这些模型现在已经开始准确地反映喷流结构中固有的复杂性。在推进我们对基本动力学过程的基本理解的同时，我们将研究气候科学中当前重要的四个具体问题：（i）平流层中痕量化学物质的系统传输;（ii）平流层和对流层环流的耦合;（iii）对流层急流气候变化的后果;（iv）与南大洋急流有关的不均匀输送和混合。该项目揭示了基础科学的进步如何有效地与特定应用驱动的定向目标相结合。

Over the last several years, the strongly inhomogeneous nature ofatmospheric and oceanic mixing in diverse situations has becomeincreasingly apparent, as high resolution numerical simulations andobservations begin to represent accurately the detailed spatialstructure of air and water masses and their constituents. Mixing isnow known to be confined to distinct latitudinal regions, oftenseparated by sharp gradients that indicate dynamical transportbarriers. Inhomogeneous mixing by waves and eddies in atmospheres andoceans is intrinsically linked to the presence of zonally alignedjets, which not only arise as a result of the eddy mixing, but alsoorganize the mixing in distinct latitudinal regions. The combinedeffect is a dynamical feedback that is now known to operate under verygeneral conditions. Inhomogeneous mixing is important for thetransport of constituents such as water vapour, carbon dioxide, ozone,heat, and salinity; their inhomogeneous re-distribution impacts bothglobal radiative balances and regional climate change.Despite recent advances, a complete understanding of the way zonaljets organize inhomogeneous mixing, in particular the verticalstructure of such mixing, remains elusive. Progress in understandingthe horizontal structure of jets and mixing has been made recently, inparticular by focusing on the potential vorticity, a key dynamicalquantity that contains information about both horizontal rotationalmotion and density stratification. The aim of this project is tobuild on that recent work to develop a complete theory for thevertical structure of jets and mixing. In doing so, it willcontribute to our understanding both of the structure of the dominantjet structures in the atmosphere and oceans, as well as providingpredictions of how they will reach dynamical equilibrium underdifferent forcing conditions, conditions that may change in a changingclimate. It is anticipated that the new theory will allow us toassess the robustness of predictions made by climate models, which arenow beginning to accurately represent the complexities inherent in jetstructures.As well as advancing our fundamental understanding of basic dynamicalprocesses, we will study four specific issues of current importance inclimate science: (i) systematic transport of trace chemicals withinthe stratosphere; (ii) the coupling of the stratospheric andtropospheric circulations; (iii) the consequences of a climatic shiftin the tropospheric jet stream; and (iv) inhomogeneous transport andmixing associated with jets in the Southern Ocean. The projecthighlights how advances in fundamental science can be effectivelycombined with directed goals driven by specific applications.