Analysis and Observations of Particle Size Distribution in Supercell Thunderstorms

超级单体雷暴中粒径分布的分析与观测

• 批准号: 0969172
• 负责人: Katja Friedrich
• 金额: $ 36.34万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-06-15 至 2014-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0969172&HistoricalAwards=false
• 关键词: Analysis; Observations; Particle; Size; Distribution

Supercell-type thunderstorms, which embody a complex arrangement of long-lasting rotating updrafts and intense downdrafts, are known to be responsible for generating most intense tornadoes. However, considerable uncertainty exists regarding mechanisms culminating in the actual focus and downward extension of stormscale rotation in the form of a damaging tornadic vortex. Some working hypotheses link this process to the strength, thermodynamic stability (temperature) and spatial configuration of downdrafts in the lowest reaches of these storms, which are in-turn dependent on rates of evaporative cooling influenced by the type and size distributions of falling hydrometeors (chiefly rain and hail.) Rigorous attempts have not yet been made to investigate the range of these microphysical precipitation characteristics beneath supercell thunderstorms. The overarching goal of this project is to i) deploy multiple mobile disdrometers (instruments that measure the characteristic sizes and fallspeeds of precipitation particles) beneath supercell thunderstorms during the second Verification of the Origins of Rotation in Tornadoes EXperiment (VORTEX2; a field program conducted over the central United States known as "tornado alley") in Spring 2010, ii) conduct a comprehensive analysis of both existing and newly-obtained disdrometer observations to determine microphysical characteristics in tornadic compared to nontornadic supercell thunderstorms, and iii) relate these results to contemporaneous high-resolution polarimetric Doppler radar observations. Both disdrometers and polarimetric Doppler radar can detect (or in the case of radar, infer) the size distributions of falling hydrometeors. While preliminary analyses have provided some insights about hydrometeor distributions and their impacts on evolution of supercell storm features, a comprehensive analysis of a number of cases using well-placed high-resolution measurements has yet to be conducted and will be achieved in the course of this work.Intellectual Merit: This project will augment our knowledge about microphysical processes within supercell thunderstorms and may lead to improved short-term forecasts and warnings of life-threatening severe weather. Since VORTEX2 hosts the largest number of polarimetric Doppler radars to ever monitor the full lifecycle of supercell thunderstorms, this experiment is an ideal laboratory to address these scientific questions. At present, the lack of skill in forecasting and understanding microphysical processes is largely due to both the inadequate representation of microphysical processes and the lack of measurements. This mobile deployment of disdrometers in VORTEX2 will provide by far the most comprehensive dataset of disdrometer and radar observations and analysis in supercell thunderstorms ever collected. Broader Impact: The improvement of short-term forecasts and warnings of severe weather is strongly linked to the representation and understanding of the microphysical processes, which will be substantially extended by this work. Results will be shared with the modeling community and integrated with other, existing VORTEX2 data sets. Results will also be disseminated through presentations at conferences, seminars, and workshops as well as through publications in relevant professional journals. Additional Broader Impacts will come through direct involvement of graduate students in collection and analysis of field datasets, as well as through enhanced classroom education at both undergraduate and graduate levels.

超级单体型雷暴体现了长期旋转上升气流和强烈下降气流的复杂排列，已知是产生最强烈龙卷风的原因。 然而，关于最终以破坏性龙卷涡形式出现的风暴规模旋转的实际焦点和向下延伸的机制，存在相当大的不确定性。 一些可行的假设将这一过程与这些风暴最低处的下降气流的强度、热力学稳定性（温度）和空间配置联系起来，而这些又又取决于受下降水汽凝结物类型和尺寸分布影响的蒸发冷却速率。主要是降雨和冰雹。）尚未进行严格的尝试来研究超级单体雷暴下这些微物理降水特征的范围。 该项目的总体目标是 i) 在第二次龙卷风旋转起源验证实验（VORTEX2；一项在2010 年春季，美国中部被称为“龙卷风巷”），ii）对现有的和新获得的进行全面分析测速仪观测以确定龙卷与非龙卷超级单体雷暴的微物理特征，以及 iii) 将这些结果与同期高分辨率偏振多普勒雷达观测联系起来。 测距仪和偏振多普勒雷达都可以检测（或者在雷达的情况下推断）下降的水凝物的尺寸分布。 虽然初步分析提供了有关水凝物分布及其对超级单体风暴特征演化影响的一些见解，但尚未使用适当的高分辨率测量对许多案例进行全面分析，并将在此过程中实现智力成果：该项目将增强我们对超级雷暴内部微物理过程的了解，并可能改善对危及生命的恶劣天气的短期预报和预警。 由于 VORTEX2 拥有数量最多的偏振多普勒雷达来监测超级单体雷暴的整个生命周期，因此该实验是解决这些科学问题的理想实验室。 目前，缺乏预测和理解微物理过程的技能很大程度上是由于微物理过程的表征不充分和测量的缺乏。 VORTEX2 中的这种移动式测距仪部署将提供迄今为止收集的超级单体雷暴中最全面的测距仪和雷达观测和分析数据集。更广泛的影响：恶劣天气短期预报和预警的改进与微物理过程的表征和理解密切相关，这项工作将大大扩展这一点。 结果将与建模社区共享，并与其他现有的 VORTEX2 数据集集成。 结果还将通过会议、研讨会和讲习班上的演讲以及相关专业期刊上的出版物进行传播。 其他更广泛的影响将通过研究生直接参与实地数据集的收集和分析以及通过加强本科生和研究生水平的课堂教育来实现。