AGS-PRF: Impacts of Microphysics and Cold Pool Thermodynamics on Supercell Tornadogenesis: Comparisons of Numerical Simulations with VORTEX2 Observations

AGS-PRF：微物理和冷池热力学对超级单体龙卷发生的影响：数值模拟与 VORTEX2 观测结果的比较

• 批准号: 1137702
• 负责人: Daniel Dawson
• 金额: $ 8.6万
• 依托单位: Dawson Daniel T
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1137702&HistoricalAwards=false
• 关键词: AGS; PRF; Impacts; Microphysics; Cold

The violent and ephemeral tornado remains one of the most challenging subjects of study in the atmospheric sciences. Tornadogenesis, maintenance, intensification and decay mechanisms are all characteristics that are still poorly understood. Each of these issues were primary motivations for the recent VORTEX2 (hereafter, V2) field campaign that took place during the Spring of 2009 and 2010 in the Great Plains of the United States. Unprecedented data on many tornadic and nontornadic supercells were acquired over the length of the project, which included rich mobile radar data, high density in situ surface observations, and proximity soundings. Within the context of this project, the surface in situ observations of surface temperature and moisture in the cold pools of the surveyed storms, as well as disdrometer observations of dropsize distributions (DSDs) coupled with polarimetric radar data, are of primary interest.Research over the past decade has indicated a clear empirical signal for tornadogenesis, intensity, and longevity to be strongly influenced by the thermodynamic properties of the associated storm cold pool. In particular, tornadoes are more likely to form, persist, and intensify, when the surface temperature and moisture deficits (relative to a suitable undisturbed near-storm environment) in the cold pool are relatively small. This research aims to investigate the causative mechanisms for this empirical correlation through an idealized numerical modeling approach. The work will leverage several diverse cases from the V2 field program to aid in initialization and verification of the model simulations. As such, it will sample a fairly large parameter space that was spanned by the V2 cases. Intellectual Merit:The research is expected to provide new insights into the relationship between supercell cold pools and tornado activity through the following means:1) Understanding the sensitivity of cold pool thermodynamics to the microphysical processes of water loading, evaporation, and melting utilizing sophisticated microphysics parameterization packages, and the variance across the spectrum of cases provided by V2;2) Assessing the impact of variation in the thermodynamic properties of the cold pools on tornadoes, and improving physical understanding of this connection;3) Verifying microphysical parameterizations through comparison with disdrometer and polarimetric radar data.Broader Impacts:The results of this research are expected to improve our ability to understand supercell storm characteristics that are most likely to produce significant tornadoes, and thus it will have a direct impact on the lives of the millions of U.S. citizens threatened or affected by tornadoes each year. The comparison between model representations of microphysical processes and the rich polarimetric radar and disdrometer datasets available from the V2 will help identify avenues for improvement of these parameterizations and thus have direct implications for forecasts of precipitation from severe convection and the associated risks of flooding and hail damage.

剧烈而短暂的龙卷风仍然是大气科学研究中最具挑战性的课题之一。 龙卷风的发生、维持、增强和衰减机制都是人们目前还知之甚少的特征。 这些问题都是 2009 年春季和 2010 年春季在美国大平原进行的 VORTEX2（以下简称 V2）实地活动的主要动机。在项目期间获得了许多龙卷风和非龙卷风超级单体的前所未有的数据，其中包括丰富的移动雷达数据、高密度原位表面观测和邻近探测。 在该项目的背景下，主要关注的是对所调查风暴的冷池中的表面温度和湿度的表面原位观测，以及与偏振雷达数据相结合的液滴尺寸分布（DSD）的测速仪观测。过去十年已经表明了一个明确的经验信号，即龙卷风的发生、强度和持续时间受到相关风暴冷池热力学特性的强烈影响。 特别是，当冷池中的表面温度和水分不足（相对于合适的未受干扰的近风暴环境）相对较小时，龙卷风更有可能形成、持续和加剧。本研究旨在通过理想化的数值建模方法来研究这种经验相关性的因果机制。这项工作将利用 V2 现场计划中的几个不同案例来帮助模型模拟的初始化和验证。 因此，它将对 V2 案例跨越的相当大的参数空间进行采样。 智力价值：该研究预计通过以下方式为超级细胞冷池与龙卷风活动之间的关系提供新的见解：1）利用复杂的微物理学了解冷池热力学对水加载、蒸发和融化的微物理过程的敏感性参数化包，以及 V2 提供的各种情况下的方差；2) 评估冷池热力学特性变化对龙卷风的影响，并提高对这种联系的物理理解；3) 验证通过与测速仪和偏振雷达数据进行比较来进行微物理参数化。更广泛的影响：这项研究的结果预计将提高我们了解最有可能产生严重龙卷风的超级单体风暴特征的能力，从而对人们的生活产生直接影响每年有数百万美国公民受到龙卷风的威胁或影响。 微物理过程的模型表示与 V2 提供的丰富的偏振雷达和测速仪数据集之间的比较将有助于确定改进这些参数化的途径，从而对强对流降水以及洪水和冰雹损害的相关风险的预测产生直接影响。