Is flood risk increasing? Exploring the relationships between atmospheric circulation, extreme rainfall and flooding

现在有一个广泛的科学共识，即全球气候正在以可能在未来几十年对我们的社会和自然环境产生重大影响的方式发生变化。全球变暖及其对极端天气事件的影响，可能会对我们未来的生活方式产生深远的影响。最近发生的极端天气事件，例如美国2005年飓风季节异常多的飓风、2002年夏天中欧史无前例的洪灾、次年夏天欧洲热浪造成的悲惨生命损失，或者2000年秋季英国的严重洪灾，都被媒体认为是全球变暖的可能影响。这使得我们把注意力集中在未来气候变化对我们社会可能产生的影响上。然而，如果我们不了解当前局地尺度的气候变率如何受更大尺度的大气控制，以及这些过程在未来可能会如何变化，我们如何预测未来全球变暖可能会如何改变极端天气事件的频率和强度及其影响？该奖学金将通过与欧洲国家大气研究中心的美国国际专家合作，以及通过与英国生态与水文学中心和环境局的联系，来研究这些和其他基础研究问题。这项研究将以英国为试验台，研究大尺度大气环流模式、局部尺度极端降雨及其对洪水的影响之间的联系。最近政府资助的Foresight项目表明，洪水每年给英国造成22亿GB的损失；8亿GB的防洪费和14亿GB的平均损失。到本世纪80年代，这一数字可能会从2 GB上升到270亿GB，这取决于我们未来如何管理温室气体排放。虽然英国洪水随时间的变化得到了合理的描述，但洪水的空间范围和严重程度的变化却没有得到很好的描述。此外，我们不了解导致严重降雨事件和洪水的大气机制，目前这些机制可能会如何变化，以及在全球变暖下这些机制可能会如何进一步变化。英国是开展这项研究的理想地点，因为它拥有丰富的水文、气候和气象数据，这项研究将首先集中于了解导致全英国洪水风险的气候过程。然后，它将使用两个案例研究--约克郡的乌斯河和坎布里亚郡的伊甸河，利用水文模型框架，研究河流集水区内对气候变化的更详细反应。虽然这项研究的重点是英国，但通过了解导致洪水的综合过程，结果将适用于世界其他地区。最后，利用对导致极端降雨事件和洪水的复杂大气过程的新理解，我将开发一种方法来调查未来气候变化对英国洪水风险的影响。这一方法将利用最新的区域和全球气候模型成果制定，并将有助于制定一个新的欧洲气候变化影响概率框架和新的工具，供管理人员用来设计对气候变化影响强大的防洪系统。正如英国政府环境、食品和农村事务部(DEFRA)最近发布的《为水创造空间》报告所指出的那样，这些措施对于未来在气候变化下管理英国集水区的洪水风险是必要的。

There is now a broad scientific consensus that the global climate is changing in ways that are likely to have a large impact on our society and the natural environment over the coming decades. Global warming, and its impact on extreme weather events, may have a profound influence on the way we live in the future. Recent extreme weather events, such as the unusual number of hurricanes in the US 2005 hurricane season, the unprecedented flooding in central Europe in summer 2002, the tragic loss of life in the European heatwave the following summer, or the severity of flooding in the UK during autumn 2000, have been said to be a possible impact of global warming by the media. This has made us focus our attention on the possible impacts of future climate change on our society. However, how can we predict how future global warming may change the frequency and intensity of extreme weather events and their impacts if we do not understand how current local scale climatic variability is governed by the larger-scale atmosphere and how these processes may change in the future? This fellowship will examine these and other fundamental research questions through collaboration with international experts in the US at the National Center for Atmospheric Research, Europe and through links with the Centre for Ecology and Hydrology and the Environment Agency in the UK. This fellowship will examine the links between large-scale atmospheric circulation patterns, local scale extreme rainfall and their impact on flooding using the UK as a test-bed. The recent government-funded Foresight project suggests that flooding costs the UK £2.2 billion annually; £800 million on flood defence and £1.4 billion average damage. This may rise to somewhere from £2 to £27 billion by the 2080s, depending on how we manage greenhouse gas emissions in the future. Whilst changes through time in UK flooding are reasonably well characterised, changes in the spatial extent and severity of flooding are not. Additionally, we do not understand the atmospheric mechanisms that cause severe rainfall events and thus flooding, how these may be currently changing and how these may further change under global warming. The UK is an ideal location for this study as it has a wealth of hydrological, climatological and meteorological data, and the study will concentrate firstly on an understanding of the climatic processes that contribute to flood risk UK-wide. It will then use two case studies, the river Ouse in Yorkshire and the river Eden in Cumbria, to look at the more detailed response to climate variability within a river catchment using a hydrological modelling framework. Although the study has a UK focus, the results will be applicable to other parts of the world, through an understanding of the processes that combine to cause flooding. Finally, using this new understanding of the complex atmospheric processes that cause extreme rainfall events and flooding, I will develop a method to investigate the impacts of future climate change on the risk of flooding in the UK. This methodology will be developed using the latest regional and global climate model outputs and will contribute to the development of a new probabilistic framework for climate change impacts in Europe and new tools that can be used by managers to design flood defence systems that are robust to the impacts of climate change. These will be necessary for the future management of flood risk in UK catchments under climate change; as indicated by the UK government's Department for Environment, Food and Rural Affairs (DEFRA) recent report 'Making Space for Water'.