Exploring co-occurring UK HYDRo-meteorological extremes that exAcerbate risk (HYDRA)

在冬季，英国(GB)的基础设施受到多种重大气象灾害的威胁，越来越明显的是，这些灾害在一个复杂但研究较少的多灾害系统中相互作用(例如，Hillier等人，2020)。例如，2022年2月戏剧性的风暴序列(达德利、尤尼斯、富兰克林)的影响表明，迫切需要对英国的多重危险风险有更复杂的看法。尤尼斯的高风速使100多万户家庭断电，并在英格兰南部造成重大交通中断(火车和航班被取消，道路被封锁)，苏格兰和英格兰北部的降雪造成了进一步的中断。在富兰克林期间，持续的大雨导致400多户家庭被淹。此外，英国有30亿英镑的直接保险损失、因山体滑坡造成的道路封闭(例如，德比郡的A57“蛇口”关闭了1个月)和其他社会影响(例如，学校和港口关闭、树木被砍伐)。这些影响强调，有必要适当考虑可能发生的严重事件，这些事件可能(I)包括多个风暴，(Ii)跨越多天，以及(Iii)呈现在不同地点出现的各种危害，并影响英国plc的各种关键系统(例如基础设施)。这与目前英国的水文气象灾害(与风和雨有关)几乎总是被分开考虑的做法形成对比(例如，英国的气候变化风险评估在很大程度上将单一天气风险归入竖井)。为了方便起见，有一些分类(例如，高温和低温对运输的风险)，并讨论了连锁故障的相关问题，但没有适用于由共同发生的危险驱动的风险的综合逻辑。同样，保险公司应用复杂的随机风险模型(例如，10,000个模拟事件)，然而内陆洪水和极端风仍然被建模为独立的和独立的。更好地了解洪水和极端风的一个关键进展是确定它们是系统地联系在一起的(Hillier等人，2015)。在这一初步观察的推动下，UKRI资助的各种项目(即UKCGFI，与劳埃德银行集团的KTP，暴风雨天气，稳健)正在为这两种危险之间的联系建立科学证据基础。作为其中的一部分，英国央行在2022年引入了一项初步(谨慎的)要求，要求保险公司在它们必须提交的压力测试中考虑到这一联系。九头蛇将把这项工作提升到一个新的水平，将这一重要的调查范围扩展到更广泛的冬季多重灾害系统(即内陆洪水、山体滑坡、极端风、风暴潮、极端寒冷、降雪)。九头蛇是一个探索性项目，旨在识别、量化和暂时解释六个关键的GB冬季极端水文气象事件如何加剧风险。九头蛇将使用历史观测(同化于ERA5，GLOFAS)和UKCP18区域气候预测，以更好地了解相关灾害将如何演变到未来。铁路和其他基础设施提供商对确定的共生事件的敏感度将在研讨会上绘制出来，结束了科学工作。九头蛇的科学是开创性的，因为目前缺乏系统的、高度多种危险的风险证据。除了对NERC科学做出贡献外，它还将通过确定基础设施网络风险建模的驱动因素来定义工程(EPSRC)挑战，并将纳入政策(通过DEFRA和CCRA)和行业(例如再保险)实践。

In wintertime, infrastructure in Great Britain (GB) is threatened by multiple significant meteorological hazards, and it is increasingly apparent that these interact in a complex yet poorly studied multi-hazard system (e.g. Hillier et al, 2020). For example, the impacts of the dramatic February 2022 storm sequence (Dudley, Eunice, Franklin) demonstrated the pressing need for a more sophisticated view of GB's multi-hazard risk. The high windspeeds of Eunice left over 1 million homes without power and caused major transport disruption (trains and flights cancelled, roads blocked) in southern England, with snow causing further disruption in Scotland and northern England. Persistent heavy rain then resulted in the flooding of >400 homes during Franklin. In addition, there was ~£3 billion in direct insurance damage, road closures due to landslips (e.g. A57 'snake pass', Derbyshire, closed for 1 month) and other societal impacts in GB (e.g. school and port closures, trees felled). The impacts underlined the need to properly account for severe episodes that might (i) encompass a number of storms, (ii) span many days, and (iii) present a variety of hazards that manifest in different locations and affect various critical systems of UK plc (e.g. infrastructure).This contrasts to current practice where GB's hydro-meteorological hazards (related to wind and rain) are almost always considered separately (e.g. the UK's Climate Change Risk Assessment very much places single weather risks into siloes). There is some grouping for convenience (e.g. risks to transport from high and low temperatures), and the related issue of cascading failure is discussed, but there is no integrated logic applied to risk driven by co-occurring hazards. Likewise, insurers apply sophisticated, stochastic risk models (e.g. >10,000 simulated events), yet inland flooding and extreme wind are still modelled as separate and independent.A critical advance to better understanding flooding and extreme wind was identifying that they were systematically linked (Hillier et al., 2015). Spurred on by this initial observation, various UKRI funded projects (i.e. UKCGFI, a KTP with Lloyds Bank Group, STORMY-WEATHER, ROBUST) are building a scientific evidence base for a link between these two hazards. As part of this, in 2022 the Bank of England introduced an initial (cautious) requirement for insurers to account for this link in the stress tests to which they must submit. HYDRA will take this work to a new level, extending this important line of enquiry to the wider wintertime multi-hazard system (i.e. inland flooding, landslide, extreme wind, storm surge, extreme cold, snow). HYDRA is an exploratory project that aims to identify, quantify, and provisionally explain how the co-occurrence of six key GB hydro-meteorological wintertime extremes exacerbates risk. HYDRA will use historical observations (assimilated in ERA5, GLOFAS) and UKCP18 regional climate projections to better understand how linked hazards will evolve into the future. Rail and other infrastructure providers' sensitivity to identified co-occurrences will then be mapped in workshops book-ending the scientific work. HYDRA's science is ground-breaking due to the lack of systematic, highly multi-hazard risk evidence currently available. In addition to contributing to NERC science, it will define the engineering (EPSRC) challenge by identifying drivers for risk modelling of infrastructure networks, and will feed into policy (via DEFRA and the CCRA) and industry (e.g. reinsurance) practice.