The South Georgia Wave Experiment (SG-WEX)

引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，有必要在数值天气预报和气候模式中表示它们的影响。重力波的来源包括从山上吹来的风、不稳定的急流和强对流。这些波可以将能量和动量从这些来源转移到更高的地方，从而对环流施加显著的“阻力”，从而将大气层的不同层结合在一起。最近的研究表明，位于强风地区的孤立的山地岛屿可能是重力波的强烈来源，对大气环流具有重大的气候学影响。然而，大多数气候和数值天气预报模式不能准确地模拟来自如此小而强烈的岛屿源的波浪，因为与模式的分辨率相比，这些岛屿太小了——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：南乔治亚岛产生的重力波的性质是什么？它们的可变性是什么？这些引力波对整个南大西洋引力波场的贡献是什么？南乔治亚岛的重力波对中间层的影响是什么？如何利用这些观测来改进模型中的引力波参数化？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，我们将在两个无线电探空仪运动中对南乔治亚岛上空和周围的重力波进行测量，其中将从南乔治亚岛发射气象气球。我们将把这些观测结果与整个南大西洋的卫星测量结果结合起来。值得注意的是，我们还将在南乔治亚部署首个大气雷达。这是一个流星雷达，它将在80 - 100公里的高度对南乔治亚州上空的中间层进行重力波（以及风、潮汐和大规模行星波）的首次测量。这些实验结果将由一项模拟工作计划加以补充，该计划将探索重力波在远离其源的地方的传播。这些观测结果将用于帮助指导发展新的、改进的、重力波的数学表示（所谓的“参数化”），使这些岛屿在用于数值天气预报和气候研究的英国气象局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，确定南乔治亚与其他波源相比的相对重要性，并调查来自南乔治亚的重力波对当地风和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.