DRAGON-WEX: The DRake pAssaGe sOuthern oceaN Wave EXperiment

重力波是一种大气波，可以由风吹过山脉、风暴、不稳定的急流和强对流产生。当波从低层大气的源头上升到平流层和中间层时，它们以“动量流”的形式输送动量。当海浪变得不稳定时，它们就会“破裂”，就像海面的海浪在海滩上破裂一样。这会将它们的动量转移到大气层中，施加“阻力”，极大地影响全球大气环流。用于数值天气预报和气候研究的计算机通用环流模型(GCM)如果要预测真实大气的行为，就必须真实地表示这些波。然而，GCM显示出“偏差”，即它们预测的行为与观测揭示的不一致。在几乎所有的GCM中，最大的偏差发生在冬季和春季的南极平流层。在那里，它们产生了一个极地区域，即“极地涡旋”，与观测值相比，在5-10K的温度下太冷了，风太强了，大约每S 10米，在春天破裂之前持续了大约2-3周。这些显著的偏差被称为“冷极”问题。现在人们意识到，这些偏差的产生是因为GCM遗漏了大量重力波通量，而这些重力波通量必须出现在南纬60度附近的实际大气中。这些纬度包括多雨的南大洋和德雷克海峡。然而，这些“失踪”的海浪的性质、来源、可变性和通量目前还很不确定。在Drake-Passage南大洋波浪实验中，我们将使用卫星、无线电探空仪和雷达直接测量南大洋和Drake Passage 60 S附近的海浪，确定它们的性质，并研究它们在对流层、平流层和中间层相互耦合中的作用。因此，我们的结果将有助于解决冷极问题。我们将应用我们开发的一种非常强大的新3D方法来分析卫星数据。使用我们的方法，我们可以在3D中探测平流层中的单个重力波，并测量它们的动量通量。重要的是，因为它是一种全3D方法，所以我们可以在不需要严格限制早期1D和2D方法的假设的情况下做到这一点。我们将使用我们的方法来识别大约100,000个60岁左右的重力波。我们将把卫星观测与无线电探空仪(天气气球)和雷达所做的重力波测量相结合，来描述“失踪”的重力波，确定它们的短期和季节变化，并调查它们的来源--特别是南安第斯山脉和南极半岛的山脉、南大洋/德雷克海峡的风暴、不稳定急流以及从纬度到南北传播到60 S地区的波对重力波的贡献。我们将使用独特的流星雷达组合，一个在南极，一个在遥远的南乔治亚岛山区，用来测量中间层的风、浪和潮汐。我们将确定我们在平流层测量的波动在多大程度上驱动中间层的可变性，特别是波在驱动最近在极地中间层近90公里高度观察到的异常事件中的作用，当时一般环流的北风似乎短暂停止，极地中间层云的出现频率大大减少。我们将使用南乔治亚岛和南极罗瑟拉的流星雷达来调查最近关于山脉产生的波可以传播到90公里或更高的高度--有效地在空间边缘--的说法。最后，在《影响之路》中，我们将与英国气象局密切合作，使用我们的结果来测试和改进他们的统一模型GCM。

Gravity waves are atmospheric waves that can be generated by winds blowing over mountains, storms, unstable jet streams and strong convection. As the waves ascend from their sources in the lower atmosphere, into the stratosphere and mesosphere, they transport momentum in a "momentum flux". When the waves become unstable they "break", rather like ocean surface waves breaking on a beach. This acts to transfer their momentum into the atmosphere, exerting a "drag force" that dramatically influences the global atmospheric circulation.Computer General Circulation Models (GCMs) used for numerical weather prediction and climate research must represent these waves realistically if they are to predict the behaviour of the real atmosphere.However, the GCMs display "biases" in which the behaviour they predict does not match that revealed by observations. The largest biases in nearly all GCMs occur in the winter and springtime Antarctic stratosphere. There, they produce a polar region, the "polar vortex", that when compared to observations, is too cold by 5-10 K, has winds that are too strong by about 10 m/s and that persists some 2-3 weeks too long into spring before it breaks up. These significant biases are known as the "cold pole" problem.It is now realised that the biases arise because the GCMs are missing large amounts of gravity-wave flux that must occur in the real atmosphere at latitudes near 60 degrees S. These latitudes include the stormy Southern Ocean and the Drake Passage. However, the nature, sources, variability and fluxes of these "missing" waves are currently very uncertain. In DRAGON-WEX (DRake pAssaGe sOuthern oceaN - Wave EXperiment) we will use satellites, radiosondes and radars to directly measure the waves over the Southern Ocean and Drake Passage near 60 S, determine their properties and investigate their role in coupling together the troposphere, stratosphere and mesosphere. Our results will thus help resolve the cold pole problem.We will apply a very powerful novel 3D method we have developed for analysing satellite data. With our method, we can detect individual gravity waves in the stratosphere in 3D and measure their momentum fluxes. Importantly, because it is a fully 3D method we can do this without the needing the assumptions that critically limit earlier 1D and 2D methods. We will use our method to identify an estimated 100,000 individual gravity waves near 60 S.We will combine the satellite observations with measurements of gravity waves made by radiosondes ("weather balloons") and radars to characterise the "missing" gravity waves, determining their short-term and seasonal variability and investigate their sources - in particular, the contributions made to the waves by the mountains of the Southern Andes and Antarctic Peninsula, storms over the Southern Ocean/Drake Passage, unstable jet streams and by waves propagating into the 60 S region from latitudes to the North or South.We will use a unique combination of meteor radars, one in the Antarctic and a new radar on the remote mountainous island of South Georgia to measure the winds, waves and tides of the mesosphere. We will determine the degree to which fluctuations in the waves we measure in the stratosphere drive the variability of the mesosphere and, in particular, the role of waves in driving anomalous events recently observed at heights near 90 km in the polar mesosphere, when the Northward winds of the general circulation appeared to briefly cease and when the occurrence frequency of polar mesospheric clouds was greatly reduced.We will use meteor radars on the island of South Georgia and at Rothera in the Antarctic to investigate recent suggestions that waves generated by mountains can propagate to heights of 90 km or more - effectively the edge of space.Finally, in Pathways to Impact we will work closely with the Met Office to use our results to test and improve their Unified Model GCM.