Observations of Severe Local Storms and Tornadoes with the Atmospheric Imaging Radar

The Atmospheric Imaging Radar (AIR) is a mobile X-band imaging weather radar system designed and built by the Advanced Radar Research Center (ARRC) at the University of Oklahoma. By transmitting a vertical, 20-degree fan beam and using a 36-element receive array, digital beamforming is used to form pulse-by-pulse RHIs with a native beamwidth of 1 degree by 1 degree. Rotation in the azimuthal dimension allows for sector scans up to 180 degrees, resulting in full 20x180 degree volumetric updates in as little as 10 seconds and 20x90 degree updates in under 6 seconds. Additionally, by utilizing pulse compression, range resolution of 30 meters and acceptable sensitivity for meteorological observations are achieved. The combination of spatial and temporal resolution allows for the observation and analysis of storm structure and evolution on extremely short timescales. The AIR has been deployed in convective field campaigns each spring in the Southern Plains since 2012 and has collected data on tornadoes, supercells, and squall lines at ranges as close as 3 km, resulting in very high spatial and temporal observations of severe convective storms. The progression of system configurations for operational use across the span of 4 years of field experiments is discussed, and recent data are presented. Features that were previously unobservable with typical scanning weather radars, as well as context regarding the implications of imaging radar for severe weather observations are discussed. Data comparisons and a discussion of beamforming options, future hardware implementations, and analysis opportunities are presented.