Enhanced Radar Studies of Severe Convective Storms and Tornadoes

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Tornadic winds loft various types of debris into the air, some of which is ingested into the tornado’s vortex. The debris is readily viewed by weather radar, but it complicates the remote measurements of tornadic winds near the ground. This research program will focus on separating debris motion from air motion in the near-surface tornado layer and investigate the relationship between tornado debris and the wind field. Research will also continue on various aspects of the steps that occur prior to the formation of a tornado. Better understanding of tornado debris has a potential impact on structural engineering and improved understanding of tornado development is important for short-term tornado forecasts. This award will also provide training for the next generation of research scientists.The research team will analyze existing radar data and execute new observations using the RaXPol radar in an attempt to separate debris motion from air motion in the tornado boundary layer. The researchers plan to test the hypothesis that air motion in the tornado boundary layer is truly convergent most of the time, not divergent as is the motion of the bulk of the scatterers owing to the centrifuging of the more massive scatterers. The goals of this aspect of the work are to determine whether the team can generate realistic radar returns using an LES-generated tornado with different types of debris and compare the signatures to RaXPol observations, and to determine if it is possible to use Doppler spectra to separate debris motion from air motion. The tornadogenesis work will involve the analysis of a set of tornado cases collected over the last decade with specific focus on sub-structures within supercells that have been documented by radar observations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.