PRAC: Understanding the development and evolution of violent tornadoes in supercell thunderstorms

每年，龙卷风在美国造成数百万至数十亿美元的财产损失。自1990年以来，平均每年有78名美国公民死于龙卷风。2011年，美国48个州发生了1,690场龙卷风，其中59场龙卷风造成553人丧生。尽管观测和建模/计算技术取得了进步，龙卷风的行为仍然是个谜。我们目前还无法预测未来的雷雨是否会产生龙卷风，更不用说它是短暂而微弱的，还是持久而强大的。这项拟议的工作将使用Blue Waters在分辨率上模拟许多不同的猛烈龙卷风，从龙卷风的产生到消散。通过模拟不同环境中的许多风暴，该项目希望确定最具破坏性的龙卷风的形成和维持所涉及的因素，并了解更多关于其结构和演化的信息。这项工作有可能改善对最具破坏性的风暴的预测，最终拯救生命。一旦在Blue Waters上的模拟中确定了与长期存在的猛烈龙卷风的发生和维持有关的具体特征，现场研究人员就可以在观测到的风暴中搜索这些特征。在运行中的天气雷达上识别出的这些特征可以帮助预报员发布针对异常猛烈的龙卷风的具体、有针对性的警告。此外，对研究中使用的代码CM1的修改将与天气模拟社区共享。在之前的工作中，该项目对蓝水进行了突破性的超高分辨率模拟(网格间距30米)，模拟了一场长期存在的猛烈龙卷风，该龙卷风是由一个超级单体催生的，该超级单体是基于2011年5月24日在俄克拉荷马州中部观察到的EF5龙卷风超级单体而产生的。该项目建议在以前工作的基础上，探索2011年5月24日风暴中龙卷风形态对云微物理、湍流参数化和低层环境风切变等参数的敏感性。此外，该项目将能够在CM1中使用任意拉伸的垂直网格，以便将分辨率集中在关键垂直级别，如靠近地面的水平。此外，该项目将以实际可行的方式应用表面摩擦，为CM1增加功能，使其能够在强烈旋转的地区对雨和冰雹进行离心，并在发生猛烈龙卷风的其他风暴环境中爆炸。最后，该项目将增加CM1的能力，将重新启动文件从较粗的网格插入到较细的网格，允许该模型模拟风暴-S生命周期的周期，其中极端分辨率集中在风暴的核心。

Each year, tornadoes cause millions to billions of dollars of property damage in the United States.Since 1990, an average of 78 U.S. citizens were killed annually by tornadoes. In2011, 553 lost their lives from 59 tornadoes out of 1,690 that occurred that year in 48 states.Despite advances in observational and modeling/computing technology, thebehavior of tornadoes remains a mystery. We are currently unable to predict whether agiven thunderstorm will produce a tornado, much less whether it will be short-lived and weak, orlong-lived and powerful. The proposed work will use Blue Waters to simulate many different violent tornadoes at resolutions in which the tornado is resolved from its genesis through its dissipation.By simulating many storms in different environments, the project hopes to identify the factors involved inthe formation and maintenance of the most devastating tornadoes, as well as learn more about itsstructure and evolution. This work has the potential to improve the forecasting of the most devastatingstorms, ultimately saving lives. Once specific features related to the genesis and maintenance oflong-lived violent tornadoes are identified in simulations on Blue Waters, field researchers can search forsuch features in observed storms. Such features identified on operational weather radar could helpforecasters issue specific, targeted warnings for unusually violent tornadoes. Furthermore, modificationsto the code used in the study, CM1, will be shared with the weather modeling community.In a prior work, the project conducted a breakthrough ultra-high resolution simulation (30 meter grid spacing) on Blue Watersof a long-lived violent tornado spawned from a supercell that was based upon the observed24 May 2011 EF5 tornadic supercell in central Oklahoma. The project proposes to build upon this previous work to explore thesensitivity of tornado morphology in the 24 May 2011 storm to parameters such as cloud microphysics,turbulence parameterization and low-level environmental wind shear. In addition, the project will enable the useof arbitrarily stretched vertical grids in CM1 in order to focus resolution at key vertical levels, suchas near the ground. Moreover, the project will apply surface friction in a physically realistic manner, add functionalityto CM1 that enables the centrifuging of rain and hail in regions of intense rotation, and exploreother storm environments in which violent tornadoes occurred. Finally, the project will add the ability for CM1 tointerpolate restart files from a coarser mesh to a finer mesh, allowing the model to simulate periodsof the storm?s life cycle where extreme resolution is focused on the core of storm.