Tornadic Storms with Doppler Polarimetric Radar

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

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.