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

大气湍流是造成空中旅行者和空乘人员在飞行中受伤的主要原因。每年有数万架飞机遭遇严重的湍流，造成数百人受伤，并造成飞机结构性损坏。例如，一家典型的航空公司每年损失超过7,000个工作日，原因是空乘人员因湍流受伤而无法工作。湍流导致了对航空旅行的恐惧（航空恐惧症），据报道，这在某种程度上影响了高达40%的人口。据估计，湍流每年会给全球航空业造成约10亿美元的损失。气候变化被认为会加强晴空湍流，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）太粗糙，无法分辨单个湍流斑块，（B）比诊断技术所能达到的分辨率粗糙一个数量级。此外，尽管对流湍流也是一种危险的、可能依赖于气候的湍流，但云中的湍流（对流湍流）对气候变化的响应以前还没有研究过。本项目将首次使用高分辨率气候模式来研究晴空湍流和对流湍流对气候变化的响应。使用~20 km的大气网格分辨率，而不是以前研究中使用的~200 km，有很多好处。首先，产生湍流的小尺度过程（如风切变和对流上升气流）将得到更精细的解析。第二，航空湍流的业务预报是在~20公里分辨率下完成的，当与飞机测量结果进行验证时，具有很高的技能分数，证明了计算的可信度。第三，因为一片湍流的平均长度是60公里，我们将第一次分辨出单个的湍流。这个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（ERA 5）相比，高分辨率气候模式模拟产生晴空湍流的过程有多好？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可用势能等巧妙的代理进行诊断）如何响应气候变化？湍流斑块尺寸分布是如何变化的？是否会有两倍大小相同的补丁，或者同样数量的补丁，但每个补丁的大小都增加了一倍？这些相反的可能性对未来的飞机操作有不同的影响。学生将与NCAS高分辨率气候模拟组密切合作，并因此获得一套高分辨率气候模拟，例如最近为CMIP 6准备的PRIMAVERA项目的一部分。从大气动力学的角度来看，这些结果不仅具有很大的学术意义，而且还将直接影响到商业航空部门，从而产生很大的非学术影响。

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.