Using the Atmospheric Imaging Radar to Study Vortex Dynamics and Debris Processes

Because of the short timescales on which tornado characteristics can change, observation platforms with high spatial and temporal resolution are necessary to properly study tornadoes. One system capable of providing such data is the Atmospheric Imaging Radar (AIR). This mobile, phased array, X-band radar transmits a fan beam (20^o elevation x 1^o azimuth) to collect data from all desired elevation angles simultaneously, without any need for mechanical steering in elevation. This is made possible by the use of digital beamforming, which is able to electronically form 1^o beams in elevation. In this study, an overview of applications of the AIR to study vortex dynamics and debris processes is shown. Specifically, three cases will be discussed: the 16 May 2015 “Tipton, OK” tornado, the 27 May 2015 “Canadian, TX” tornado, and the 19 May 2013 “Shawnee, OK” tornado. In the Tipton, OK tornado, debris lofting patterns are studied, along with possible causes for enhanced debris lofting such as increased low-level convergence. Additionally, a distinct periodicity in tornado couplet intensity within the lowest 300-400 m AGL is presented. In the Canadian, TX tornado, changes in vortex tilt are shown, as well as concentric weak-echo holes (WEHs), indicating debris lofting. Finally, enhanced debris loading and rapid changes to the WEH in the Shawnee, OK tornado are discussed. All three of these cases are utilized to show how the high temporal resolution provided by a phased array radar aids in assessing rapid changes to the vortex structure and debris characteristics of a tornado at close range.