Near-Surface Thunderstorm Outflow Characteristics Observed by the TTUKa Mobile Doppler Radars

Severe convective outflow events are of interest to the wind engineering community as they are the dominant extreme wind type for much of the inland midlatitudes. However, turbulence characteristics, such as gust factor and turbulence intensity, of severe convective outflow have been rarely documented and are limited to point measurements from anemometers. The ability of Doppler radars to observe the mean and standard deviation, represented by the spectrum width for low-elevation angle scans in the absence of strong horizontal wind shear, of a wind field suggests that the turbulence intensity and gust factor can be remotely sensed over a broad region.

This study will assess the ability of two Ka-band mobile Doppler radars (TTUKa) to observe the turbulence characteristics of thunderstorm outflow. TTUKa-derived turbulence intensities and gust factors within three internal rear-flank downdraft (RFD) surges of the 18 May 2010 Dumas, Texas supercell observed by VORTEX2 will be presented in an effort to gauge the influence of interaction with the surface on the intensity and behavior of the surges. Additionally, turbulence characteristics from the Dumas supercell will be compared to those calculated from single-Doppler plan position indicator scans (PPIs) and dual-Doppler syntheses at a low elevation angle collected within the outflow of a mesoscale convective system on 15 June 2012 at the Texas Tech University Wind Science and Engineering Field Site west of Lubbock, Texas. The location of the 15 June TTUKa deployment allows turbulence intensities and gust factors calculated from Doppler radar observations to be compared to point measurements by a 200 m instrumented tower located within the dual-Doppler domain.