VORTEX2: Multiscale Analyses of Tornadic Storms Using Multiparameter Mobile Radars

学术价值：龙卷风实验2(旋涡2)中旋转起源的验证是对导致龙卷风发生的因素进行的多尺度调查。涡旋2是涡旋1的后续，涡旋1的场阶段是在1994年和1995年春季进行的。涡旋1提高了对龙卷风和非龙卷风的运动学结构的认识，并提供了一些关于超单体风暴和龙卷风的演化对非常精细的空间尺度非均质性的敏感性的线索。涡旋2社区打算在涡旋1成果的基础上加以扩展和发展。这项提议支持的研究涉及影响龙卷风风暴涡度发展和分布的风暴尺度环流以及热力和降水变率。这些研究目标共有的主要数据集是对龙卷风母体及其邻近环境的整个宽度和深度的多普勒和偏振雷达观测。需要C波段雷达，既能穿透强降水，又能感知与超级单体风暴相关的晴空气流。虽然首席调查员将使用两个C波段覆盖风暴的整个深度，但将使用X波段双极化雷达对风暴最低3公里处进行频繁的协调采样，以研究中气旋下方后侧下沉气流和角动量的微物理和动力学。这三个雷达将密切协调，以提供风暴规模的环流和降水结构，以将来自其他仪器的更精细的观测放入更大规模的风暴和环境流动的背景下。这项研究的科学目标是研究：(1)与超级单体低层旋转有关的涡度动力学；(2)角动量转移对龙卷风发生的作用；(3)后侧下沉气流的降水和热力学；(4)环境异质性(包括边界)对风暴演变的影响；(5)单体合并对龙卷风发生的作用；(6)龙卷风和非龙卷风超级单体内极化特征的演变；以及(7)利用集合卡尔曼滤波数据同化改进龙卷风的分析和预报。更广泛的影响：根据1997年关于天气的社会和经济影响的讲习班，龙卷风每年造成约73人死亡，平均经济影响约为7亿美元。虽然随着美国国家气象局(NWS)的多普勒现代化和预报员培训计划的实施，与龙卷风警报相关的提前时间有所增加，但错误报警率基本上保持不变。错误警报得不到改善，反映出对可能导致或限制龙卷风发生的物理过程缺乏了解。在这里进行的研究将提高基础知识，使更好的概念模型和提高预测能力。改进的数据同化和数值天气预报技术将有助于预报员努力更好地警告公众。独立的双极化和多多普勒风场将有助于风暴过程和模式验证的研究。双极化数据将提供与龙卷风发生有关的极化特征的早期指示，如果存在的话，这将最大限度地受益于国家气象局作战雷达网的双极化升级。这些数据集还将用于从大学新生入门到研究生阶段学期项目的大学课堂。将开发以计算机为基础的教学模块，并向社区提供。

Intellectual merit: The Verification of Origins of Rotation in Tornadoes Experiment #2 (VORTEX 2) is a multi-scale investigation of factors that lead to tornadogenesis. VORTEX 2 is a follow on to VORTEX 1 whose field phase was conducted during the Spring of 1994 and 1995. The VORTEX 1 advanced knowledge of the kinematic structures of tornadic and nontornadic storms and provided some hints as to the sensitivity of the evolution of supercell storms and tornadogenesis to very fine spatial scale heterogeneity. The VORTEX 2 community intends to extend and build upon the results of VORTEX 1. The research supported under this proposal addresses the stormscale circulations, and thermodynamic and precipitation variability that affect the development and distribution of vorticity in tornadic storms. The primary data set common to these research objectives are Doppler and polarimetric radar observations over the entire breadth and depth of the parent tornadic storm and its immediate environment. C-band radars, with their ability to both penetrate heavy precipitation and sense the clear-air inflow associated with supercell storms, are required. Although the Principal Investigators will cover the entire depth of the storm with two C-bands, frequent coordinated sampling of the lowest 3 kilometers will be made with a X-band dual-polarimetric radar to examine the microphysics and dynamics of the rear-flank downdraft and angular momentum beneath the mesocyclone. These three radars will be tightly coordinated to provide the storm-scale circulation and precipitation structure needed to place finer-scale observations from other instruments into the context of larger-scale storm and environmental flow. The scientific objectives of this research are to study: (i) vorticity dynamics associated with low-level rotation in supercells, (ii) the role of angular momentum transfer on tornadogenesis (iii) precipitation and thermodynamics of the rear-flank downdraft, (iv) the impact of environmental heterogeneity (including boundaries) on storm evolution, (v) the role of cell mergers on tornadogenesis, (vi) the evolution of polarimetric signatures within tornadic and non-tornadic supercells, and (vii) improvements in the analysis and forecasting of tornadic storms through the use of ensemble Kalman-filtering data assimilation. Broader impacts: According to the 1997 Workshop on Societal and Economic Impacts of Weather, tornadic storms account for about 73 fatalities each year and have an average economic impact of about $700M. While lead times associated with tornado warnings have increased with the National Weather Service (NWS) Doppler modernization and forecaster training program, false alarm rates have essentially remained flat. The lack of improvement in false alarms reflects lack of understanding of the physical processes that can cause or limit tornadogenesis. The research conducted here will improve fundamental knowledge, enabling better conceptual models and improved forecasting ability. The improved data assimilation and numerical weather prediction techniques will aid forecasters in their efforts to better warn the public. The independent dual-polarization and multiple-Doppler derived wind fields will aid in storm process and model validation studies. The dual-polarization data will provide an early indication of polarimetric signatures associated with tornadogenesis, if they exist, which will maximize the benefit of the dual-polarimetric upgrade of the NWS operational radar network. The datasets will also be used in university classes from freshman orientation to graduate level term projects. Computer-based teaching modules will be developed and made available to the community.