Collaborative Research: Improved Understanding/Prediction of Severe Convective Storms and Attendant Phenomena through Advanced Numerical Simulation

这项研究的目的是通过使用先进的数值模拟来提高对强对流风暴及其伴随现象的认识。 重点领域包括：1）影响龙卷风发生、强度和寿命的环境和模式参数;2）使用改进的模式物理的龙卷风表示;3）影响低层旋转强度和寿命的多风暴相互作用;4）2003年5月30日重建超级单体线的分析和模拟;5）由于快速环境变化的龙卷风发生;6）风暴尺度同化的进展：ENKF使用极化雷达数据。有几个主题连接这些领域。 其中一个主题集中在低层风暴旋转及其与龙卷风发生、演变和衰减的关系，特别是在超级单体中。 上述焦点不仅旨在通过高分辨率数值模拟提高理解，而且还旨在解释产生长路径龙卷风的风暴的结构和行为。 与这些调查相结合，将重点放在改善强风暴内的微物理表现上。 为了更准确地描述风暴和龙卷风的演变、相关的地面天气以及正确地同化偏振雷达数据，需要先进的微物理学。 目前常用的简单单矩微物理参数化不能同时正确地表示飑线和超级单体，不能可靠地预报超级单体降水，也不能完全代表偏振雷达观测到的模拟超级单体内的微物理。另一个主题是现有风暴与自身或边界的相互作用。 1996年4月19日，强烈的风暴行为的动机，一个重点扩展了最初的工作，旨在了解合并的风暴在多单体和超级单体环境中，导致风暴强度增加，风暴旋转，并增加龙卷风的潜力。 这项调查将受益于国家超级计算应用中心正在开发的新技术，以及NSF资助的LEAD ITR项目，用于管理，挖掘和可视化大型模拟集。 另一个重点是了解某些线路的重建性质，例如2003年5月30日发生的线路。 对这一事件的观测分析之后将进行数值模拟，以研究这是通过加强辐合发生的假设，辐合位于盛行冷锋与最南端超级单体的向南移动流出边界相互作用的地方，扩展的微物理学的实施和测试将为其他风暴模拟者提供关于重要微物理过程的投入。 它还将向短期预报员提供指示，说明复杂的物理学对风暴规模模型预报的影响。 此外，考虑到国家气象局可能很快升级WSR-88 D雷达网络，以包括偏振测量，需要进行初步工作，以了解如何最好地将这些测量同化到风暴尺度预报模型中，以及哪些微物理方案可以最好地结合这些新的测量。

The objective of this research is to improve understanding of severe convective storms and attendant phenomena through the use of advanced numerical simulation. Areas of focus include1) environmental and model parameters influencing tornado genesis, intensity, and longevity;2) tornado representation using improved model physics;3) multiple storm interactions influencing the intensity and longevity of low-level rotation;4) analysis and simulation of the 30 May 2003 back-building supercell line;5) tornadogenesis owing to rapid environmental changes;6) advances in storm scale assimilation: ENKF using polarimetric radar data.There are several themes that connect these areas. One theme centers on low-level storm rotation and its relationship to tornado genesis, evolution, and decay, particularly within supercells. Not only are the above foci aimed at improved understanding through high resolution numerical simulations but also at explaining the structure and behavior of storms that produce long track tornadoes. Coupled with these investigations will be a focus on improving the microphysical representation within severe storms. Advanced microphysics is needed for more accurate depiction of storm and tornado evolution, associated surface weather, and proper assimilation of polarimetric radar data. The simple single moment microphysics parameterizations commonly used today do not properly represent squall lines and supercells simultaneously, cannot forecast supercell precipitation reliably, and incompletely represent the microphysics within simulated supercells as observed by polarimetric radar.Another theme centers on the interaction of existing storms with themselves or with the presence of a boundary. Motivated by severe storm behavior on 19 April 1996, one focus extends initial work aimed at understanding mergers of storms in multicell and supercell environments that result in increased storm strength, storm rotation, and increased tornadic potential. This investigation will benefit from new technologies being developed at the National Center for Supercomputing Applications and with the NSF funded LEAD ITR project for managing, mining, and visualizing large sets of simulations. Another focus is aimed at understanding the back-building nature of some lines such as the one that occurred on 30 May 2003. Observational analysis of this event will be followed by numerical simulations to study the hypothesis that this occurs through enhanced convergence located where the prevailing cold front interacts with a southward moving outflow boundary of the southernmost supercell.The implementation and testing of expanded microphysics will provide input to others storm modelers on the important microphysical processes. It will also provide an indication to short-term forecasters of the impact that sophisticated physics can have on storm-scale model forecasts. Furthermore, given that the National Weather Service may soon upgrade the WSR-88D radar network to include polarimetric measurements, preliminary work is needed to understand how to best assimilate such measurements into storm-scale forecast models and which microphysics schemes can best incorporate these new measurements.