Improving the Understanding and Prediction of Nocturnal Convection through Advance Data Assimilation and Ensemble Simulations for Plains Elevated Convection At Night (PECAN)

研究人员早就确定，在北美大平原的大片地区，夏季雷暴和对流降水最频繁的不是在下午，而是在日落之后。夜间降水对该地区的水文和农业生产至关重要，夜间中尺度有组织的对流常常伴随着恶劣天气。然而，描述夜间对流如何在夜间发起和演化的概念框架仍然缺乏，夜间对流的预测仍然是一个科学和技术挑战。为了提高我们对夜间对流的了解和预测能力，计划于2015年6月1日至7月15日在俄克拉荷马州、堪萨斯州和内布拉斯加州的部分地区进行平原夜间高空对流(山核桃)现场试验。山核桃有望收集史无前例的观测数据，捕捉夜间对流的多尺度特征。这些数据不仅将通过观测分析促进对与夜间对流有关的关键过程的了解，而且还将使研究人员能够利用先进的数据同化(DA)和集合模拟系统来显著促进对夜间对流系统的理解和预测。本研究的重点是山核桃的预测成分，同时也对山核桃的其他三个成分做出了重大贡献。具体地说，这项研究寻求资金用于：1)通过生成实时的允许对流的集合预报来支持山核桃的干运行和场相，该集合预报使用基于高级集合的DA和集合预报系统来初始化；2)同化特殊的山核桃观测，包括地面遥感，并将这些模拟与实时模拟和观测进行比较，以评估独特的山核桃观测在提高预报技能方面的作用；3)综合诊断集合分析和模拟，以确定启动和维持夜间对流的动力和物理过程，并控制其结构和演变；4)根据特殊的山核桃观测，综合评估集合分析和预报，以确定适当的模拟策略(例如，网格间距；物理参数化)，以改进预报。智力上的好处：这一努力将促进我们对控制夜间对流系统的启动、维持、演变和结构的过程的了解。这些目标将通过重点关注下一代允许对流的模型和先进的DA技术来实现。该项目下的模拟将在其他山核桃研究人员专注于山核桃数据观测分析和理想化建模之间的努力之间发挥重要作用。这项工作还将通过对模拟的分析和与观测的比较，解决钻孔和稳定层扰动在维持提升的夜间系统中所起的内在作用。集合诊断将允许对允许对流的模式模拟再现这些关键过程的能力进行新的评估。这些研究成果将为推进高影响对流天气事件的DA策略、模式物理和观测策略提供新的见解。广泛影响：这项研究将解决天气研究的最重要目标之一-提高我们准确预测造成重大经济损失和伤亡的强烈危险天气的能力。它将直接涉及天气方面的三个既定国家优先事项：作为下一代航空运输系统的关键组成部分的下一代预报系统--高影响天气预报警告，以及从地面上观测天气和气候：全国网络网络。它将在高级发展议程和高分辨率集合模拟和数值预测领域提供急需的教育和培训，并使下一代建模和发展议程专家接受重大科学实地实验。这些研究结果具有直接的可操作性，因为将要使用的总体DA系统是基于新的美国业务DA系统开发的，并且由于PI在PI中的重要作用和/或PI与NOAA国家强风暴实验室(NSSL)、国家环境预测中心(NCEP)风暴预测中心(SPC)和环境建模中心(EMC)的联系。

Researchers have long established that summer thunderstorms and convective precipitation are most frequent not in the afternoon, but after sunset over a large swath of the Great Plains of North America. Nocturnal rainfall is critical to the hydrology and agriculture of this region, and nocturnal mesoscale organized convection is often accompanied by severe weather. However, a conceptual framework describing how nocturnal convection initiates and evolves at night is still lacking, and the prediction of nocturnal convection still remains a scientific and technical challenge. To improve both our understanding of and our ability to forecast nocturnal convection, the Plains Elevated Convection At Night (PECAN) field experiment is planned to occur across portions of Oklahoma, Kansas and Nebraska from June 1 to 15 July 2015. PECAN promises to collect unprecedented observations that capture the multi-scale aspects of nocturnal convection. Such data will not only advance the understanding of key processes associated with nocturnal convection through observational analysis , but also will enable investigators to use advanced data assimilation (DA) and ensemble modeling systems to significantly advance both the understanding and prediction of nocturnal convective systems. This research focuses on the prediction component of PECAN, but also makes major contributions to the other three components of PECAN. Specifically, this research seeks funding to : 1) Support the dry run and field-phase of PECAN through generation of real-time convection-permitting ensemble forecasts initialized using an advanced ensemble based DA and ensemble forecast system; 2) Assimilate special PECAN observations including ground-based remote sensing and compare these simulations against the real-time simulations and the observations to assess the role that the unique PECAN observations play in improving predictive skill; 3) Comprehensively diagnose the ensemble analyses and simulations to determine the dynamical and physical processes that initiate and maintain nocturnal convection and control their structure and evolution; 4) Comprehensively evaluate ensemble analyses and forecasts against special PECAN observations to determine the appropriate modeling strategies (e.g., grid spacing; physical parameterization) for improved prediction.Intellectual Merit :This effort will advance our knowledge of the processes that control the initiation, maintenance, evolution and structure of elevated nocturnal convective systems. These goals will be accomplished through a focus on the next generation of convection-permitting models and advanced DA techniques. The simulations under this project will play an important role in bridging between efforts of other PECAN investigators focused on observational analysis of PECAN data and on idealized modeling. This effort will also address the inherent role that bores and stable layer disturbances play in the maintenance of elevated nocturnal systems through analysis of simulations and comparison against observations. Ensemble diagnostics will allow for a novel assessment of the capability of a convection-permitting model simulation to reproduce these key processes. The research findings will provide new insights into advancing DA strategies, model physics and observing strategies of high impact convective weather events.Broader Impacts :This research will address one of the most important goals of weather research - to improve our ability to accurately predict intense hazardous weather that causes large monetary loss, injuries and fatalities. It will directly address three established national priorities in weather: Warn on Forecast for High Impact Weather, the Next-Generation Forecast System, as key component of the Next-Generation Air Transportation System, and Observing Weather and Climate from the Ground Up: A Nationwide Network of Networks. It will provide much needed education and training in the areas of advanced DA and high-resolution ensemble modeling and numerical prediction and expose the next generation of modeling and DA experts to a major scientific field experiment. The research findings have a direct path to operations because the ensemble DA system to be used is developed based on the new US operational DA system, and because of the significant roles of the PIs in and/or linkage of the PIs have made with NOAA National Severe Storm Lab (NSSL), National Centers for Environmental Prediction (NCEP) Storm Prediction Center (SPC) and Environmental Modeling Center (EMC).