CAREER: Multiscale Investigation of Warm-Season Precipitation Extremes

这项研究将在多个空间和时间尺度上研究与中纬度暖季极端降水有关的过程和可预报性。尽管非常需要准确的降水预报和洪水预警，但暖季强降雨的预报仍然是天气预报中最大的挑战之一。研究产生极端降雨和致命洪水的天气系统将为我们提供对这些系统的基本了解。这项研究的最终目标是改进对导致极端暖季降水的天气系统的预测。这项研究将确定增强或限制暖季对流系统可预报性的机制。智力上的优点。这项研究的一个重点将是高空中尺度对流系统(MCSs)，这些系统已经被观测到会产生极端的局地降雨和山洪暴发。缺乏关于上升的、有组织的对流的知识，限制了对潜在的山洪暴发情况进行准确预报和警告的能力。为了解决这个问题，将进行数值模拟来量化对高空线性MCSs的启动、组织和降水产生的大尺度控制，特别是热带、副热带和中纬度影响的各自作用。这些模拟还将与观测相结合，量化这些MCS演变过程中锋生环流和对流尺度过程之间的相互作用。在更大范围内，大范围、多天的暴雨事件，如2007年影响美国南部平原和2008年影响中西部的暴雨，将产生深远的影响。在一些情况下，暴雨的发生与深对流活动与大气中层长期缓慢移动的环流的发展和维持之间的一系列反馈有关。初步研究表明，像这样的事件在中期内的可预测性很低。这项研究将创建与这种中尺度环流相关的暴雨的观测气候学。然后，集合预报数据将被用来评估这些事件的可预报性，导致它们发展和数值预报成败的过程，以及它们的更大范围的影响。极端降水及其预测的不确定性也可能对社会产生相当大的影响。这项研究将研究和教育结合在一起，向大气科学领域的学生介绍探索这些影响的研究方法。研究生将接受现有社会科学方法的培训，并将开发一门多学科的本科课程，为讨论和探讨天气与社会之间的关系提供基础。通过对当地洪水和山洪事件进行学生设计的社会分析，将加强上述极端降雨的气象研究。一个地区性研讨会将把学生、研究人员、从业者和利益攸关方聚集在一起，以建立新的合作关系，并应对与极端降雨相关的复杂挑战。此外，对天气事件的综合分析将吸引公众参与，并将揭示从气象和社会角度可以改进预报和警告的领域。

This study will examine the processes and predictability associated with midlatitude warm-season extreme precipitation on multiple spatial and temporal scales. Despite the great need for accurate precipitation forecasts and flood warnings, the prediction of warm-season heavy rainfall continues to be one of the greatest challenges in weather forecasting. Investigating the weather systems that produce extreme rainfall and deadly flash flooding will provide us with basic understanding of these systems.The ultimate goal of this research is to improve prediction of the weather systems that lead to extreme warm-season precipitation. This research will identify the mechanisms that enhance or limit predictability in warm-season convective systems. Intellectual merit. One focus of this research will be elevated, linear mesoscale convective systems (MCSs) that have been observed to produce extreme local rainfall and flash flooding. The lack of knowledge about elevated, organized convection limits the ability to produce accurate forecasts and warnings of potential flash-flood situations. To address this issue, numerical simulations will be conducted to quantify the large-scale controls on the initiation, organization, and rainfall production of elevated linear MCSs, particularly the respective roles of tropical, subtropical, and midlatitude influences. These simulations will also be combined with observations to quantify the interactions between frontogenetical circulations and convective-scale processes in the evolution of these MCSs.At larger scales, widespread, multiple-day heavy rainfall events, such as those that affected the Southern Plains of the United States in 2007 and the Midwest in 2008, have far-reaching impacts. In some cases, the heavy rainfall occurs in association with a series of feedbacks between deep convective activity and the development and maintenance of long-lived, slow-moving circulations at the mid-levels of the atmosphere. Preliminary research has shown that events such as this have low predictability at the medium range. This research will create an observational climatology of heavy rainfall associated with such mesoscale circulations. Then, ensemble forecast data will be used to assess the predictability of these events, the processes that lead to their development and to the success or failure of numerical forecasts, and their larger-scale effects.Broader impacts. Extreme precipitation, and uncertainties in predicting it, can also have considerable impacts on society. This study integrates research and education by introducing students in the atmospheric sciences to research methods that explore these impacts. Graduate students will be trained in established social-science methods, and a multidisciplinary undergraduate course will be developed to provide the basis for discussions and inquiry into the relationship between weather and society. The meteorological research on extreme rainfall described above will be enhanced by performing student-designed societal analyses of local flood and flash-flood events. A regional workshop will bring together students, researchers, practitioners, and stakeholders to forge new collaborations and to address the complex challenges associated with extreme rainfall. Furthermore, integrated analyses of weather events will engage the public, and will reveal areas where forecasts and warnings can be improved from both the meteorological and societal perspective.