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一大片日落之后。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往往伴随着恶劣天气。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，计划于2015年6月1日至7月15日在俄克拉荷马州、堪萨斯和内布拉斯加州的部分地区进行夜间平原高架对流（PECAN）现场实验。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）和集合建模系统来显着推进对夜间对流系统的理解和预测。本研究的重点是PECAN的预测组件，但也作出了重大贡献的PECAN的其他三个组成部分。具体而言，本研究寻求资金：1）通过使用先进的集合基于DA和集合预报系统初始化的实时对流允许集合预报的生成来支持PECAN的试运行和现场阶段; 2）同化包括地面遥感在内的PECAN特别观测数据，并将这些模拟数据与真实的数据进行比较。时间模拟和观测，以评估独特的PECAN观测在提高预测技能方面发挥的作用;第三章全面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，控制它们的结构和演变; 4）根据特殊的PECAN观测结果全面评估集合分析和预报，以确定适当的建模策略（例如，网格间距;智力上的优点：这一努力将推进我们的知识过程控制的启动，维持，演变和结构的夜间升高对流系统。这些目标将通过关注下一代对流允许模型和先进的DA技术来实现。该项目下的模拟将发挥重要作用，在其他PECAN研究人员的努力之间的桥梁，侧重于PECAN数据的观测分析和理想化建模。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高架夜间系统中所起的固有作用。包围诊断将允许一个新的评估能力的对流允许模型模拟重现这些关键过程。研究结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。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重大经济损失、伤亡的强烈危险天气的能力。它将直接解决天气方面的三个既定国家优先事项：对高影响天气预报的警告，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，以及从地面观察天气和气候：全国网络网络。它将提供先进的DA和高分辨率集成建模和数值预报领域急需的教育和培训，并使下一代建模和DA专家接触到重大的科学现场实验。研究结果具有直接的操作路径，因为要使用的集合DA系统是基于新的美国操作DA系统开发的，并且因为PI在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）和环境模拟中心（EMC）中的重要作用和/或PI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).