Tornadic Storms with Doppler Polarimetric Radar

该项目利用多普勒偏振雷达探索微物理过程和降水在龙卷风发生中的作用。这项研究利用了为俄克拉荷马州中部的几个龙卷风收集的独特的多参数雷达数据集，以及国家严重风暴实验室(NSSL)的WSR-88D雷达(Koun)极化原型、研究双极化Cimarron雷达、C波段移动智能雷达和KTLX实战WSR-88D雷达。在这项研究的三年期间将收集更多的数据。正在对所有现有的极化变量、水平和垂直极化的双多普勒速度场和多普勒谱进行综合分析，以解决三个主要问题：首先，对一些龙卷风和非龙卷风超级单体风暴的极化特征进行详细的3D分析，以检查极化模式的时间演变及其与龙卷风发生的可能关系，并建立龙卷风和非龙卷风超级单体风暴的极化特征之间的差异。将注意力集中在最近发现的基于表面的小尺度极化碎片特征(这对于龙卷风探测非常有希望)和作为龙卷风前兆的高空更大尺度的极化模式。其次，研究了正交极化下的多普勒谱，以评估它们在龙卷风探测中的有效性，以及在雷达分辨率体积上区分低惯性(雨)和大惯性(冰雹、碎片)散射体的可能性。由于Koun WSR-88D雷达能够在雷达全覆盖区域内的每个门记录两个正交极化的时间序列数据，因此可以对雷达回波进行全面的频谱分析。第三，通过数值模拟强垂直空气运动、风切变和涡旋环流的存在，解释了观测到的极化和光谱雷达特征。此外，龙卷风风暴中的水流星轨迹利用从双多普勒分析中恢复的空气速度场进行了检查。鉴于美国国家气象局天气雷达即将在不久的将来升级到偏振能力，该项目具有广泛的潜在影响。更好的龙卷风探测和预报，以及利用改进的微物理将极化雷达数据同化到风暴尺度的数值模式中的可能性，可以改进对龙卷风的预报。教育部分包括俄克拉何马大学新的雷达和仪器课程的主要研究人员的参与，跨学科的联合建议，以及由NSF资助的本科生教育(DUE)项目中的跨学科研究。

This project explores the role of microphysical processes and precipitation in tornadogenesis using Doppler polarimetric radars. The research capitalizes on the unique multiparameter radar dataset collected for several tornadic storms in central Oklahoma with the National Severe Storms Laboratory's (NSSL) polarimetric prototype of the WSR-88D radar (KOUN), research dual-polarization Cimarron radar, C-band mobile SMART radars, and the KTLX operational WSR-88D radar. More data will be collected over the 3-year period of the study. Comprehensive analysis of all available polarimetric variables, dual-Doppler velocity fields, and Doppler spectra at horizontal and vertical polarizations are being conducted to address three major topics: First, a detailed 3D analyses of the polarimetric signatures for a number of tornadic and nontornadic supercell storms are performed to examine the temporal evolution of polarimetric patterns and their possible relation to tornado occurrence, and to establish the difference between polarimetric signatures in tornadic and nontornadic supercell storms. Attention is focused on the recently discovered surface-based, small-scale polarimetric debris signature (which is very promising for tornado detection) and larger-scale polarimetric patterns aloft as possible tornado precursors.Second, Doppler spectra at orthogonal polarizations are examined in order to evaluate their utility for tornado detection, and for possible discrimination between low-inertia (rain) and high-inertia (hail, debris) scatterers in the radar resolution volume. Comprehensive spectral analysis of radar echoes is possible because of the unique capability of the KOUN WSR-88D radar to record time series data at two orthogonal polarizations at every gate in a full radar coverage area.Third, the observed polarimetric and spectral radar signatures are interpreted using numerical modeling of precipitation development in the presence of strong vertical air motions, wind shear, and vortex circulation. In addition, hydrometeor trajectories in the tornadic storms are examined using the air velocity fields retrieved from a dual-Doppler analysis.The project has broad potential impact in light of the upcoming upgrade of the National Weather Service weather radars to polarimetric ability in the near future. Better tornado detection and prediction as well as possible assimilation of polarimetric radar data into storm-scale numerical models with improved microphysics can lead to improved forecasts of tornadoes. Educational components include participation of the principal investigators in the new Radar and Instrumentation Curriculum at the University of Oklahoma, co-advising across disciplines, and inter-disciplinary research in the funded NSF undergraduate Education (DUE) project.