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，夏季雷暴和对流降水最频繁的不是在下午，而是在北美大平原的大片地区日落之后。夜间降雨对该地区的水文和农业至关重要，夜间中尺度有组织对流常伴有恶劣天气。然而，描述夜间对流如何在夜间开始和演变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理解和预测能力，平原夜间高架对流（PECAN）野外实验计划于2015年6月1日至7月15日在俄克拉何马州、堪萨斯州和内布拉斯加州的部分地区进行。PECAN承诺收集前所未有的观测数据，捕捉夜间对流的多尺度方面。这些数据不仅将通过观测分析促进对与夜间对流相关的关键过程的理解，而且还将使研究人员能够使用先进的数据同化（DA）和集成建模系统来显著推进对夜间对流系统的理解和预测。本研究的重点是PECAN的预测部分，但对PECAN的其他三个部分也有重要贡献。具体而言，本研究寻求资金支持：1)通过使用先进的基于集合的数据分析和集合预报系统初始化生成允许对流的实时集合预报，支持PECAN的干运行和现场阶段；2)吸收包括地面遥感在内的特殊PECAN观测数据，并将其与实时模拟和观测数据进行比较，评估PECAN独特观测数据对提高预测技能的作用；3)综合诊断集合分析和模拟，以确定夜间对流的启动和维持以及控制其结构和演变的动力和物理过程；4)根据特殊的PECAN观测综合评价集合分析和预测，以确定适当的建模策略（如网格间距；物理参数化）以改进预测。智力价值：这一努力将推进我们对夜间高空对流系统的启动、维持、演化和结构控制过程的认识。这些目标将通过关注下一代对流允许模型和先进的数据分析技术来实现。该项目的模拟将在其他PECAN研究人员专注于PECAN数据的观测分析和理想化建模之间发挥重要的桥梁作用。这项工作还将通过模拟分析和与观测结果的比较，解决钻孔和稳定层扰动在维持夜间高架系统中所起的内在作用。集成诊断将允许对允许对流的模型模拟的能力进行新的评估，以重现这些关键过程。研究结果将为推进数据分析策略、模式物理和高影响对流天气事件的观测策略提供新的见解。更广泛的影响：这项研究将解决天气研究最重要的目标之一——提高我们准确预测导致大量金钱损失、伤害和死亡的强烈危险天气的能力。它将直接解决三个国家在天气方面的优先事项：高影响天气预警预报，下一代预报系统，作为下一代航空运输系统的关键组成部分，以及从地面观测天气和气候：全国网络的网络。它将在高级数据分析、高分辨率集成建模和数值预测领域提供急需的教育和培训，并将下一代建模和数据分析专家暴露在重大的科学领域实验中。研究结果具有直接的操作路径，因为所使用的集成数据分析系统是基于新的美国业务数据分析系统开发的，并且由于pi在与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pi联系中发挥了重要作用。

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).