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到数十亿美元的财产损失。自1990年以来，每年平均有78名美国公民死于龙卷风。2011年，在48个州发生的1690次龙卷风中，有59次造成553人死亡。尽管观测和建模/计算技术取得了进步，但龙卷风的行为仍然是一个谜。我们目前无法预测雷暴是否会产生龙卷风，更不用说它是短暂而微弱的，还是长期而强大的。拟议的工作将使用蓝色水域模拟许多不同的强烈龙卷风的分辨率，其中龙卷风从起源到消散都被解决了。通过模拟不同环境下的许多风暴，该项目希望能够确定影响最具破坏性龙卷风形成和维持的因素，并更多地了解其结构和演变。这项工作有可能改善对最具破坏性风暴的预测，最终挽救生命。一旦在蓝水模拟中确定了与长寿命强龙卷风的发生和维持有关的特定特征，现场研究人员就可以在观测到的风暴中寻找这些特征。这些在气象雷达上识别的特征可以帮助预报员对异常猛烈的龙卷风发出具体的、有针对性的警告。此外，对研究中使用的代码CM1的修改将与天气建模社区共享。在之前的一项工作中，该项目对蓝水进行了突破性的超高分辨率模拟（30米网格间距），该模拟是基于2011年5月24日俄克拉荷马州中部EF5龙卷风超级单体观测到的超级单体产生的长寿命剧烈龙卷风。该项目建议在先前工作的基础上，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，该项目将允许在CM1中使用任意拉伸的垂直网格，以便在关键垂直水平（例如靠近地面）集中分辨率。此外，该项目将以物理上真实的方式应用表面摩擦，为CM1增加功能，使强旋转区域的雨和冰雹能够离心，并探索发生强烈龙卷风的其他风暴环境。最后，该项目将增加CM1从粗网格到细网格插值重启文件的能力，允许模型模拟风暴的周期。S生命周期，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.