Using high-resolution climate models to predict increases in atmospheric turbulence

大气乱流是航空旅客和空乘人员在飞行中受伤的主要原因。每年有数以万计的飞机遭遇严重的乱流，造成数百人受伤，并造成飞机结构损坏。例如，一家典型的航空公司每年损失超过7000个工作日，因为空乘人员因气流受伤而无法工作。动荡会导致人们对航空旅行的恐惧（恐航症），据报道，高达40%的人口在某种程度上受到影响。据估计，湍流每年给全球航空业造成的损失约为10亿美元。气候变化被认为正在加强晴空湍流，这是一种特别危险的形式，因为它无法被机载雷达探测到。然而，我们目前对这一趋势的认识是基于气候模式模拟的，其空间分辨率(a)过于粗糙，无法解决单个湍流斑块；(b)比诊断已被证明是熟练的分辨率要粗一个数量级。此外，云中的湍流（对流湍流）对气候变化的响应以前没有被研究过，尽管对流湍流也很危险并且可能取决于气候。该项目将首次使用高分辨率气候模型来研究晴空湍流和对流湍流如何响应气候变化。使用~20公里的大气网格分辨率有很多好处，而不是以前研究中使用的~200公里。首先，产生湍流的小规模过程（如风切变和对流上升气流）将得到更精细的解决。其次，航空湍流的业务预报是在约20公里的分辨率下完成的，并且在与飞机测量结果进行验证时具有很高的技能分数，表明了对计算的信心。第三，由于一片湍流的中位长度是60公里，我们将首次解决单个湍流斑块。这开启了提出以前无法回答的新的科学问题的可能性。该博士项目将考虑以下研究问题：-与新获得的高分辨率再分析数据（ERA5）相比，高分辨率气候模式对产生晴空湍流过程的模拟效果如何？在这些模型中，晴空湍流是如何对气候变化做出反应的？-在高分辨率气候模式中，对流湍流（使用诸如对流降水率和对流有效势能等技术指标诊断）如何响应气候变化？-湍流补丁的大小分布是如何变化的？会有两倍的相同大小的补丁，还是相同数量的补丁，但每个补丁的大小都是原来的两倍？这些相反的可能性对未来的飞机操作有不同的影响。该学生将与国家科学院高分辨率气候模拟小组密切合作，并因此获得一套高分辨率气候模拟，例如最近为cmip6准备的那些，作为PRIMAVERA项目的一部分。从大气动力学的角度来看，这些结果具有很大的学术价值，它们也将直接影响商业航空部门，从而产生很高的非学术影响。

Atmospheric turbulence is the leading cause of in-flight injuries to air travellers and flight attendants.Tens of thousands of aircraft encounter severe turbulence annually, injuring hundreds of people andcausing structural damage to planes. For example, a typical airline loses over 7,000 working daysannually, due to flight attendants being injured by turbulence and unable to work. Turbulencecontributes to the fear of air travel (aviophobia), which reportedly affects up to 40% of the populationto some degree. Turbulence is estimated to cost the global aviation sector around one billion dollarsannually.Climate change is thought to be strengthening clear-air turbulence, which is a particularly hazardousform, because it is undetectable by on-board radar. However, our current knowledge of this trend isbased on climate model simulations whose spatial resolution is (a) too coarse to resolve individualpatches of turbulence and (b) an order of magnitude coarser than the resolution at which thediagnostics have been shown to be skilful. Furthermore, the response of turbulence in clouds(convective turbulence) to climate change has not previously been studied, even though convectiveturbulence is also hazardous and likely to depend on climate.This project will use high-resolution climate models for the first time to investigate how clear-airturbulence and convective turbulence respond to climate change. There are many benefits of usingan atmospheric grid resolution of ~20 km, rather than the ~200 km used in previous studies. First, thesmall-scale processes that generate turbulence (such as wind shear and convective updrafts) will beresolved in much finer detail. Second, operational forecasts of aviation turbulence are done at ~20 kmresolution and have high skill scores when verified against aircraft measurements, demonstratingconfidence in the calculations. And third, because the median length of a patch of turbulence is60 km, we will be resolving individual patches of turbulence for the first time. This opens up thepossibility of asking new scientific questions that were previously unanswerable.This PhD project will consider the following research questions:- How well do high-resolution climate models simulate the processes generating clear-airturbulence, compared to newly available high-resolution reanalysis data (ERA5)? How doesclear-air turbulence respond to climate change in these models?- How does convective turbulence (diagnosed using skilful proxies such as the convectiveprecipitation rate and convective available potential energy) respond to climate change in high-resolution climate models?- How do the turbulence patch size distributions change? Will there be twice as many patchesof the same size, or the same number of patches but each doubled in size? These oppositepossibilities have different implications for future aircraft operations.The student will work closely with the NCAS high-resolution climate modelling group, and will therebygain access to a set of high-resolution climate simulations, such as those recently prepared for CMIP6as part of the PRIMAVERA project. As well as the results being of great academic interest from anatmospheric dynamics perspective, they will also be of direct interest to the commercial aviationsector, leading to a high non-academic impact.