High-Resolution Tornado Observations Using the Atmospheric Imaging Radar

The Advanced Radar Research Center (ARRC) at the University of Oklahoma has designed and built a mobile imaging weather radar system called the Atmospheric Imaging Radar (AIR). By using digital beamforming techniques, the AIR can simultaneously collect data for an entire vertical cross-section illuminated by a wide transmit beam. As a result, update times are significantly shorter than with existing mobile radars, including other phased-array radar systems. Since the receive antenna of the AIR is a phased array, proper calibration is necessary to ensure accurate measurements. Moreover, there exist many beamforming techniques in the literature, each offering its own distinct advantages and disadvantages. This paper presents the calibration algorithm used by the AIR, and shows data collected by the AIR while observing a tornado near Carmen, OK on April 14, 2012. Several beamforming techniques are evaluated and the first-ever simultaneous cross-section measurements through a tornado are presented to illustrate the advantages of this unique weather radar.