Overview of the Atmospheric Imaging Radar and Seven Years of Phased-Array Radar Field Experiments

Rapid-scan observations from phased array radars offer substantial potential to improve scientific understanding and prediction of rapidly evolving phenomena (e.g., tornadoes). The Atmospheric Imaging Radar (AIR) is an X-band mobile phased array radar that was developed with the primary goal of obtaining rapid-scan observations in close proximity to severe local storms. The AIR transmits a 20º spoiled (or fan) beam and operates a 36-element receive array oriented in the same vertical plane. Rather than mechanically or electronically steering the beam in the vertical direction, the AIR applies digital beamforming to the received data in postprocessing to form 1º beams within the transmit beam and obtain nearly instantaneous RHI scans. By mechanically scanning in azimuth, the AIR is able to obtain 180º-by-20º volumetric sector scan in only 5 to 10 s.

Since 2012, OU scientists, engineers, and students have participated in convective field experiments to collect AIR observations of severe thunderstorms and other phenomena. To date, the AIR team has collected numerous rapid-scan observations of supercells and tornadoes, including violent tornadoes during the 2013 tornado outbreaks. In this study, an overview of AIR observations and scientific findings to date will be presented. The first part of the AIR overview will highlight cases from tornadic supercells, including observations of tornado formation and dissipation and analyses of tornado intensity and debris changes in mature tornadoes. The second part of the overview will focus on non-tornadic cases, including multicellular convection and cold front cases. Possible applications of AIR findings and digital beamforming to a future operational PAR network will also be discussed.