Structure and transport properties of jets in the atmosphere and oceans

在过去几年中，随着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组成的详细空间结构，大气和海洋混合在不同情况下的强烈不均匀性变得越来越明显。现在已知混合仅限于不同的纬度区域，通常由表明动力输运屏障的陡峭梯度分隔。大气和海洋中波浪和涡旋的不均匀混合与纬向排列射流的存在有着内在的联系，纬向排列射流不仅是涡旋混合的结果，而且还将混合组织在不同的纬向区域。组合效应是一种动态反馈，现在已知它在非常普遍的条件下起作用。不均匀混合对于水汽、二氧化碳、臭氧、热量和盐度等成分的输送很重要；它们的不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，但对纬向射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难以捉摸。在理解射流和混合的水平结构方面取得了进展，特别是在关注位势涡度方面，位势涡度是一个包含水平旋转运动和密度分层信息的关键动态量。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主要喷流结构的结构，并提供它们如何在不同强迫条件下达到动力平衡的预测，这些条件可能在不断变化的气候中发生变化。预计新的理论将使我们能够评估气候模型预测的稳健性，这些模型现在开始准确地代表喷气机结构固有的复杂性。除了推进我们对基本动力学过程的基本理解外，我们还将研究当前重要的气候科学的四个具体问题：(i)平流层中微量化学物质的系统运输；（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非均匀输送和混合。该项目凸显了基础科学的进步如何与特定应用驱动的定向目标有效结合。

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.