The South Georgia Wave Experiment (SG-WEX)

重力波是大气波的一种重要类型。它们在许多大气过程中发挥着关键作用，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反映重力波的影响是至关重要的。重力波是由山上吹来的风、急流不稳定和强对流等源产生的。这些波可以将能量和动量从这些来源输送出去，并将它们堆积在更高的高度，从而对环流施加显著的“阻力”，从而将不同层次的大气耦合在一起。最近的研究表明，强风地区与世隔绝的山区岛屿可能是重力波的强烈来源，可能会对大气环流产生气候上的重大影响。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来源的海浪，因为与模型的分辨率相比，岛屿太小--这就是“小岛屿问题”。在这里，我们建议进行一项大型协调观测和模拟实验，以确定所有这些岛屿中最重要的岛屿--南大西洋的南乔治亚岛--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.南乔治亚产生的重力波的性质是什么？它们的变异性是什么？2.这些重力波对南大西洋上空重力波的总场有什么贡献？3.来自南乔治亚的重力波对中间层有什么影响？4.如何利用这些观测来改进模式中的重力波参数化？5.与其他重力波源相比，南乔治亚有多重要？它如何影响当地的风和天气系统的发展？为了回答这些问题，我们将对以下几个问题进行测量南乔治亚州上空和周围的重力波在两次无线电探空活动中，气象气球将从南乔治亚州发射。我们将把这些观测与整个南大西洋的卫星测量联系起来。值得注意的是，我们还将在南乔治亚州部署第一台大气雷达。这是一台流星雷达，将首次在南乔治亚州上空80-100公里高度的中间层测量重力波(以及风、潮汐和大尺度行星波)。这些实验结果将得到一项探索重力波远离其来源的传播的模拟工作方案的补充。这些观测将被用来帮助指导发展新的、改进的、重力波的数学表示法(所谓的“参数化”)，从而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，模拟研究将综合这些研究，确定南乔治亚州与其他波源相比的相对重要性，并调查来自南乔治亚州的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.