PREEVENTS Track 2: Collaborative Research: Improving High-Impact Hail Event Forecasts by Linking Hail Environments and Modeled Hailstorm Processes

美国每年因破坏性的冰雹风暴而遭受数十亿美元的保险损失，而且这种风暴造成的社会和经济损失一直在增加。仅2017年一年，美国就有超过1000万处财产被冰雹破坏。最近的灾难性冰雹事件包括2017年影响丹佛的损失23亿美元的冰雹事件，2016年4月圣安东尼奥损失14亿美元的冰雹事件，其中包括4.5英寸的冰雹，以及2012年德克萨斯州阿马里洛的冰雹风暴，造成200万米的冰雹漂移，冲刷道路，导致交通瘫痪。不幸的是，这些事件都没有提前预料到。这项建议将确定什么样的环境会产生如此高的影响冰雹事件，以及产生冰雹的物理过程如何受到环境过程的影响。对冰雹增长的更好理解将被纳入国家天气预报模式中的冰雹预报系统，以改进冰雹预报，这与NSF促进国民健康、繁荣和福利以及保障国防的使命是一致的。随着短期(1小时)冰雹预报的改进，可以避免迫在眉睫的威胁，例如建议户外体育场或活动的参观者避难。改进的中期预报(1-3天)可能会产生需要更多时间密集规划的建议行动，例如移动掩体下的飞机，通知保险理算员，并与县级应急管理人员合作，为公共户外活动制定应急计划。除了冰雹的大小之外，了解预计的冰雹类型，如大冰雹或大量小冰雹(或“暴雪”冰雹)，将使天气预报员能够更好地为公众做好准备：例如，预测的“暴风雪”冰雹事件可能需要一个城市准备好耕作设备，并建议公众避开可能发生洪水的低洼地区。此外，了解哪些环境与哪些冰雹事件类型有关，对于在更长的时间尺度上、从亚季节尺度到季节性尺度乃至更远的尺度上发展冰雹预报来说，是一个必要的步骤。该提案还将支持一名获得博士学位的研究生、两名获得硕士学位的研究生和三名本科生。为了提高可预测性，减少冰雹对社会日益重要的影响，该提案将实现以下四个目标：1)确定不同冰雹威胁级别(例如，大冰雹或10厘米或4英寸、大量小冰雹)对冰雹生产的环境控制，并确定区域、季节和地区差异。2)建立冰雹威胁级别发生与环境条件之间的物理关系。确定哪些胚胎源区特征增加了不同类别冰雹威胁的有利冰雹增长轨迹的概率，以及这些特征在现实风暴环境中的变化情况。3)根据最新可用的时变雷达反演的风场和浮力场以及地面冰雹观测，验证微物理复杂冰雹轨迹模型。4)将有关环境控制、三维冰雹轨迹和胚胎源区的新知识整合到CAM-HAILCAST冰雹模型中，以改进对冰雹威胁的业务预报。目标1将使用风暴预报中心(SPC)提供的广泛的冰雹邻近探测数据库来探索环境控制。目标2将使用理想化的模拟来探索对环境条件和微物理过程的敏感性。目标3将使用新开发的雷达派生的风和微物理数据集来驱动冰雹轨迹模式，该模式将通过地面冰雹观测得到验证。最后，将根据SPC数据库中的冰雹威胁事件的一个独立子集对目标4中开发的改进的冰雹预报模型进行测试。这项拟议的研究将提高对冰雹在环境和风暴尺度上增长的基本过程以及这些过程如何在不同环境中变化的理解。它将确定哪些环境最有利于不同的冰雹威胁级别(如大冰雹或大量小冰雹)或冰雹大小。它还超越了纯粹的统计学努力，以确保每个冰雹威胁级别的环境控制背后的物理过程被理解，包括大的上升量，有利的胚胎来源区域的放置，以及适当的胚胎大小。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The United States suffers billions of dollars in insured losses each year from damaging hail storms and the societal and economic costs of such storms have been increasing. Over 10 million properties in the U.S. were damaged by hail in 2017 alone. Recent examples of catastrophic hailstorms include a $2.3 billion loss hail event impacting Denver in 2017, a $1.4 billion loss hail event in San Antonio in April 2016 that included 4.5+ inch hailstones, and a 2012 hailstorm in Amarillo, TX that produced 2-m drifts of hail that washed out roads and brought traffic to a standstill. Unfortunately, none of these events were anticipated ahead of time. This proposal will identify what type of environments produce such high impact hail events, and how the physical processes that produce hail are affected by environmental processes. The improved understanding of hail growth will be incorporated into a hail forecasting system within national weather prediction models to improve hail forecasts, which is in line with NSF's mission to advance national health, prosperity and welfare and to secure the national defense. With improved short-term ( 1 h) hail forecasts, immediate threats could be avoided, such as recommending that attendees at outdoor stadiums or events take shelter. Improved intermediate-term forecasts (1-3 days) could result in recommended action that required more time-intensive planning, such as moving aircraft under shelter, notifying insurance adjusters, and working with county-level emergency managers to have contingency plans in place for public outdoor events. Knowledge of the expected type of event, such as giant hail or lots of small hail (or "blizzard" hail), in addition to merely hail size, would allow forecasters to better prepare the public: for example, a forecasted "blizzard" hail event might require a city to ready its plowing equipment and advise the public to avoid low-lying areas that could potentially flood. Additionally, knowledge of which environments are connected to which hail events types is a necessary step for developing hail forecasts on longer time scales, of subseasonal to seasonal scale and beyond. This proposal will also support a graduate student receiving a Ph.D. degree, two graduate students receiving M.S. degrees, and three undergraduate students.In order to advance predictability and reduce the increasingly significant impact of hail on society, this proposal will accomplish the following four goals: 1) Identify environmental controls on hail production for different hail threat classes (e.g., giant hail or 10 cm or 4 in, large amounts of small hail) and identify regime, seasonal and regional differences.2) Establish the physical relationship between hail threat class occurrence and environmental conditions. Determine what embryo source region characteristics increase the probability of favorable hail growth trajectories for different classes of hail threats and how these vary across realistic storm environments.3) Validate a microphysically complex hail trajectory model in light of newly available time-varying radar-retrieved wind and buoyancy fields and surface hail observations.4) Integrate new knowledge about environmental controls, three-dimensional hail trajectories, and embryo source regions into the CAM-HAILCAST hail model to improve operational forecasts of hail threats.Objective 1 will use an extensive hailstorm proximity sounding database available from the Storm Prediction Center (SPC) to explore environmental controls. Objective 2 will use idealized simulations to explore sensitivity to both environmental conditions and microphysical processes. Objective 3 will use a newly-developed radar-derived wind and microphysical dataset to drive a hail trajectory model which will be validated with surface hail observations. Finally, the improved hail forecasting model developed in Objective 4 will be tested against an independent subset of hail threat events from the SPC database. This proposed research will improve understanding of the basic processes underlying hail growth on both environmental- and storm-scales and how those vary across environments. It will determine which environments are most favorable to different hail threat classes (such as giant hail or large amounts of small hail) or hail sizes. It also moves beyond a purely statistical endeavor to ensure the physical processes underlying the environmental controls for each hail threat class are understood, including large updraft volumes, favorable placement of embryo source regions, and appropriate embryo sizes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.