PRESTO (PREcipitation STructures over Orography)

山洪暴发每年在英国造成生命损失和数十亿英镑的损失，并通过持久的影响给社会带来额外的损失，包括抑郁症风险增加四倍。由于这些事件的严重危害和长期后果，必须准确地了解和预测它们。英国山洪事件背后的三个主要机制中有两个是对流风暴和地形降水(另一个是锋面系统)。近年来，一系列毁灭性事件加强了它们的影响。2004年的博斯卡斯尔洪水和2008年的奥特里圣玛丽冰雹都是由准静止对流风暴引起的，2005年的卡莱尔洪水和2009年的科克茅斯洪水都是由地形增强的降雨引起的。虽然对流和地形可能会独立地产生极端降雨，但在英国复杂的地形上，它们往往是密切相关的。在条件不稳定流动中，陡峭地形的上游、上方和下风方向的机械上升以及由于加热升高而导致的热驱动上升是主要的对流启动机制。由于地形在空间上是固定的，这些风暴可能会锚定到特定的地形特征，并将它们的降水集中在首选地区。尤其是，准静止降水带是地形对流的一种表现，这种对流极大地增加了洪水风险，因为它们集中在特定地区的强降水。这类事件在地形分水岭上尤其令人担忧，由于其陡峭的峡谷和封闭的盆地，极易发生洪水。由于高分辨率雷达系统，在包括日本、地中海地区、落基山脉、美国太平洋西北部和加勒比海岛屿在内的许多山区都观测到了准静止对流带。在即将开展的地中海水文循环(HyMeX)方案期间，计划在法国中部山区建立一个专门的带状地形对流观测网，这反映了这些波段的水文气象重要性。尽管这些乐队在英国也会定期发展，但它们以前很少受到关注。此外，以前的大多数研究都集中在特定的个例上，并没有普遍地确定有利于它们形成的环境条件、导致它们发展的机制，或者它们在数值模式中的可预测性。拟议的工作将在英国和其他地区对准静止地形对流的理解和预测方面取得飞跃。这将通过对全球几个有连续雷达数据的区域进行密集的气候学分析来实现，这将确定支持这些波段的环境条件及其特征位置和地形。互补的高分辨率数值模拟将查明数值天气预报模式中波段及其可预报性背后的潜在机制。这项工作将为预测界、公众和该领域的其他学者提供积极的影响。预报员将受益于识别简单的诊断方法，这些诊断方法可用于根据现有的模式预报和/或上游探测来预测这些事件。建议开展一系列活动，直接与预报员接触，以便有效地传播我们的研究结果。公众将受益于对潜在危险降水事件的改进预报。学术界将受益于先进的物理理解(将通过会议、讲习班和同行评议的出版物传播)以及与该项目相关的众多国际合作。

Flash floods cause loss of life and billions of pounds of damage each year within the UK, and take an additional toll on society through lasting impacts including a four-fold enhancement in the risk of depression. Because of the acute hazards and long-term consequences of these events, it is essential that they be accurately understood and predicted. Two of the three principal mechanisms behind UK flash-flooding events are convective storms and orographic precipitation (the other being frontal systems). Their impact has been reinforced in recent years by a series of devastating events. The Boscastle flood of 2004 and the Ottery St Mary's hailstorm of 2008 were both caused by quasi-stationary convective storms, and the Carlisle flood of 2005 and Cockermouth flood of 2009 were both caused by orographically enhanced rainfall. Although convection and orography may act independently to produce extreme rainfall, they are often closely linked over the complex UK terrain. The mechanical ascent upstream, over, and downwind of steep terrain and the thermally-driven ascent due to elevated heating are primary convection-initiation mechanisms in conditionally unstable flows. Because orography is fixed in space, these storms may anchor to specific terrain features and focus their precipitation over preferred areas. In particular, quasi-stationary precipitation bands are a manifestation of orographic convection that greatly increases flood risks because they focus heavy precipitation over specific regions. Such events are of particular concern over orographic watersheds, which, due to their steep gorges and confined basins, are highly susceptible to floods.Thanks to the high resolution radar systems, quasi-stationary convective bands have been observed over numerous mountain regions including Japan, the Mediterranean region, Rocky Mountains, Pacific Northwest United States, and Caribbean islands. The hydro-meteorological importance of these bands is reflected by the planned installation of a dedicated observational network for banded orographic convection over the French Massif Central during the upcoming Hydrological Cycle in the Mediterranean (HyMEX) programme. Although these bands also develop regularly over the UK, they have received little previous attention. Moreover, the majority of previous studies have focused on specific cases and have not generally identified the environmental conditions that favour their formation, the mechanisms that cause them to develop, or their predictability in numerical models.The proposed work will provide a leap forward in the understanding and prediction of quasi-stationary orographic convection in the UK and beyond. This will be achieved through an intensive climatological analysis over several regions of the globe where continuous radar data is available, which will identify the environmental conditions that support the bands and their characteristic locations and morphologies. Complementary high-resolution numerical simulations will pinpoint the underlying mechanisms behind the bands and their predictability in numerical weather prediction models. This work will provide positive impacts for the forecasting community, general public, and other academics in the field. Forecasters will benefit from the identification of simple diagnostics that can be used operationally to predict these events based on available model forecasts and/or upstream soundings. A series of activities are proposed to directly engage with forecasters to effectively disseminate our findings. The public will benefit from improved forecasting of potentially hazardous precipitation events. The academic community will benefit from the advanced physical understanding (which will be disseminated through conferences, workshops, and peer-reviewed publications) and the numerous international collaborations associated with this project.