The South Georgia Wave Experiment (SG-WEX)

重力波是一种重要的大气波。它们在许多大气过程中发挥关键作用，从对流到化学物质的混合，再到影响平流层和中间层的全球尺度环流。因此，在数值天气预报和气候模式中体现重力波的影响是非常重要的。重力波的来源包括吹过山脉的风、急流不稳定性和强对流。这些波可以将能量和动量从这些源中传输出去，并将它们存款在更高的高度，从而对环流产生显著的“阻力”，从而将大气的不同层耦合在一起。最近的研究表明，强风地区的孤立山区岛屿可能是重力波的强烈来源，对大气环流产生重大的气候影响。然而，大多数气候和数值天气预报模型无法准确地模拟来自如此小而强烈的岛屿源的波浪，因为与模型的分辨率相比，岛屿太小了-这就是“小岛问题”。在这里，我们提出了一个主要的协调观测和建模实验，以确定所有这些岛屿中最重要的，南大西洋的南格鲁吉亚产生的重力波的性质和影响。我们的实验将回答以下问题：1.南格鲁吉亚产生的重力波的性质是什么？它们的变化是什么？2.这些重力波对南大西洋重力波总场的贡献是什么？3.来自南格鲁吉亚的重力波对中间层有什么影响？4.如何利用这些观测结果来改进模型中的引力波参数化？5.与其他重力波源相比，南格鲁吉亚有多重要？它如何影响当地风和天气系统的发展？为了回答这些问题，我们将在两次无线电探空仪活动中测量南格鲁吉亚上空和周围的重力波，其中气象气球将从南格鲁吉亚发射。我们将把这些观测结果与整个南大西洋的卫星测量结果联系起来。重要的是，我们还将在南格鲁吉亚部署第一个大气雷达。这是一个流星雷达，将首次测量南格鲁吉亚上空80 - 100公里高度中间层的重力波（以及风、潮汐和大规模行星波），这些实验结果将得到一个模拟工作方案的补充，该方案将探索重力波远离其来源的传播。这些观测结果将用于帮助指导开发新的、改进的重力波数学表示（所谓的“参数化”），使这些岛屿在气象局用于数值天气预报和气候研究的统一模型中得到更好的表示。最后，模拟研究将整合这些研究，并确定南格鲁吉亚与其他波源相比的相对重要性，并调查南格鲁吉亚重力波对当地风和天气（天气）系统发展的影响。

Gravity waves are an important type of atmospheric wave. They play a key role in many atmospheric processes, ranging from convection to the mixing of chemical species to influencing the global-scale circulation of the stratosphere and mesosphere. Because of this, it is essential to represent their effects in numerical weather prediction and climate models.Gravity waves are generated by sources including winds blowing over mountains, jet-stream instabilities and strong convection. The waves can transport energy and momentum away from these sources and deposit them at greater heights, thus exerting a significant "drag" on the circulation and so coupling together different layers of the atmosphere. Recent studies have shown that isolated mountainous islands in regions of strong winds can be intense sources of gravity waves that can have climatologically-significant effects on atmospheric circulation. However, most climate and numerical weather prediction models cannot accurately model waves from such small, intense island sources because the islands are too small compared to the resolution of the models - this is the "small island problem". Here, we propose a major coordinated observational and modelling experiment to determine the nature and impacts of gravity waves generated by the most important of all these islands, South Georgia in the Southern Atlantic. Our experiment will answer the following questions:1. What is the nature of gravity waves generated by South Georgia and what is their variability?2. What is the contribution of these gravity waves to the total field of gravity waves over the South Atlantic?3. What is the influence of gravity waves from South Georgia on the mesosphere?4. How can these observations be used to improve gravity-wave parametrizations in models?5. How important is South Georgia in comparison to other gravity-wave sources and how does it impact local winds and the development of synoptic systems?To answer these questions we will make measurements of gravity waves over and around South Georgia in two radiosondes campaigns in which meteorological balloons will be launched from South Georgia. We will place these observations in context with measurements made by satellite across the whole South Atlantic. Significantly, we will also deploy the first atmospheric radar on South Georgia. This is a meteor radar that will make the first ever measurements of gravity waves (and winds, tides and large-scale planetary waves) in the mesosphere over South Georgia at heights of 80 - 100 km.These experimental results will be complemented by a programme of modelling work that will explore the propagation of gravity waves away from their sources. The observations will be used to help guide the development of new, improved, mathematical representations of gravity waves (so-called "parametrizations") allowing such islands to be better represented in the Met Office's Unified Model used for numerical weather prediction and climate studies. Finally, modelling studies will integrate these studies and determine the relative importance of South Georgia compared to other waves sources and investigate the impact ofGravity waves from South Georgia on local winds and the development of synoptic (weather) systems.