A global climatology of sting-jet cyclones

冬季风暴，正式名称为中纬度或热带外气旋，是中纬度地区的主要自然灾害。它们可以造成与飓风一样大的破坏，尽管风力稍弱，因为它们的锋面很长，可以超过1000公里。破坏可能来自极端的风，雨和风暴潮，具有异常强风的风暴通常被称为风暴。自2015年以来，气象局已命名所有影响英国的风暴，这些风暴有可能导致琥珀色或红色天气警报，以改善即将发生的潜在危险天气的沟通;通常每年发生约7场命名风暴（以及更多未命名风暴）。自2004年对1987年十月大风暴的观测结果进行重新审查以来，已经在一些影响英国的最具破坏性的中纬度气旋中发现了刺痛射流。据报道，这场风暴造成的损失为63亿美元（与2012年的价值挂钩）。刺状喷流是从云头内部下降几个小时的连贯气流，云头是一条云带，围绕着强烈的气旋中心向极地弯曲。这些喷流与其他寿命更长、规模更大、特征更好的近地表风喷流不同。虽然它们的风足迹通常只有50-100公里宽，但它们可以导致异常强烈的近地表风和破坏性阵风的不同区域。自首次识别以来，我们对尾喷流动力学的理解已经有了相当大的进展，但主要是通过分析穿越北大西洋影响西北欧的气旋的案例研究。最近发表了一个起源于地中海的刺喷流活动的案例，但其他中纬度地区没有发表的案例，发表的气候学只涵盖北大西洋。尽管如此，没有已知的物理原因，为什么刺痛射流不应该发展在其他海洋盆地和类型的大气不稳定性与刺痛射流已被证明是广泛的中纬度海洋。该项目将产生第一个全球性的刺流气旋气候学，并分析这些气旋与不含刺流的气旋之间的差异。我们将应用一个刺式喷气环境前兆工具识别和跟踪再分析数据中的气旋。再分析数据提供了过去天气和气候的最完整的表示，并通过使用一致的现代天气预报模型将观测结果与天气预报相结合而生成。尾喷流的瞬时、相对小尺度的性质以及与其产生相关的大气不稳定性的类型意味着它们只能由具有非常高分辨率的模型来表示（即，在空间上紧密分离的点处求解运动方程），这些点通常在数据周期和/或区域性质上受到限制。前兆工具旨在诊断有助于在多年代际全球数据集中形成尾喷流的环境条件，例如再分析，这些数据集分辨率太粗，无法代表尾喷流。这项工作将利用项目小组成员以前的工作来开发前兆，最近，提高其计算效率，作为气象局将其作为预报工具的一部分（它被应用于真实的时间预报输出），以及从最新的ECMWF再分析ERA 5（从1979年至今可用）得出的气旋路径的可用性。这些创新意味着全球气候学现在是可行的。由此产生的气候学将揭示在南半球，北太平洋，北大西洋和欧洲大陆上空的刺急流的存在和频率。这项研究将为全面评估刺射流旋风在现在和未来几年的影响铺平道路。

Winter storms, formally called mid-latitude or extra-tropical cyclones, are a major natural hazard in the midlatitudes. They can cause as much damage as hurricanes, despite somewhat weaker winds, due to their long fronts that can trail for more than 1000 km. Damage can come from extreme wind, rain and storm surge, and storms with exceptionally strong winds are often called windstorms. Since 2015 the Met Office has named all storms impacting the UK that have the potential to cause an amber or red weather warning to improve the communication of impending potentially dangerous weather; typically about 7 named storms (and many more unnamed storms) occur each year. Sting jets have been identified in some of the most damaging mid-latitude cyclones that have affected the UK since their first identification in 2004 from a re-examination of observations of the 1987 Great October Storm. The damage caused by this storm is indicated by the reported insured loss of $6.3bn (indexed to 2012 values). Sting jets are coherent airflows that descend over a few hours from within the cloud head, a band of cloud that hooks poleward around the centre of intense cyclones. These jets are distinct from the other longer-lived, broader-scale and much better characterised near-surface wind jets. While their wind footprints are typically just 50-100 km across, they can lead to distinct regions of exceptionally strong near-surface winds, and damaging gusts. Our understanding of the dynamics of sting jets has advanced considerably since their first identification, but mostly through analysis of case studies of cyclones crossing the North Atlantic to affect northwest Europe. A single case of sting-jet activity originating in the Mediterranean has recently been published, but no published cases exist for other mid-latitude regions and published climatologies only cover the North Atlantic. Despite this, there are no known physical reasons why sting jets should not develop over other oceanic basins and the type of atmospheric instability associated with sting jets has been shown to be widespread over the mid-latitude oceans. This project will produce the first global climatology of sting-jet cyclones and characterise the differences between these cyclones and cyclones that do not contain sting jets. We will apply a sting-jet environmental precursor tool to cyclones identified and tracked in reanalysis data. Reanalysis data provide the most complete representation of past weather and climate and are generated by blending observations with weather forecasts rerun using a consistent modern weather forecast model. The transient, relatively small-scale nature of sting jets and the type of atmospheric instability associated with their generation mean that they can only be represented by models with very high resolution (i.e., the equations of motion are solved at points that are closely separated in space) which are typically limited in data period and/or regional in nature. The precursor tool is designed to diagnose environmental conditions conducive to sting jet formation in multi-decadal, global datasets, such as reanalyses, that have too coarse resolution to represent sting jets.This work will exploit previous work by members of the project team to develop the precursor and, more recently, improve its computational efficiency as part of work to implement it at the Met Office as a forecast tool (it is applied to forecast output in real time), as well as the availability of cyclone tracks derived from the latest ECMWF reanalysis, ERA5 (which is available from 1979 to the present day). These innovations mean that a global climatology is now feasible. The resulting climatology will reveal the presence and frequency of sting jets over the southern hemisphere, North Pacific, and North Atlantic oceans, and continental Europe. This research will pave the way to a comprehensive evaluation of the impact of sting-jet cyclones in present and future years.