Using a Four–Face Phased Array Radar to Detect Tornadoes and Mesocyclones: A Simulation Study

The National Weather Radar Testbed was established in Norman, OK in 2002 to evaluate, in part, the feasibility of eventually replacing mechanically scanned parabolic antennas with electronically scanned phased array antennas on weather surveillance radars. A basic characteristic of a phased array antenna is that the beamwidth increases when the beam scans away from the direction that is perpendicular to the antenna's surface. If a phased array antenna system is to replace the current parabolic antenna, among the important decisions that must be made are (1) the design (flat faces, cylinder, etc.) that will be needed to cover 360 deg in azimuth and (2) the choice of an acceptable beamwidth. Investigating the flat–face option, four faces seem to be a reasonable choice for providing adequate azimuthal resolution. To help with the beamwidth decision–making process, we investigated the influence of beamwidth on the resolution of various–sized simulated vortices. We found that the half–power beamwidth across the antenna should be no more than 1.0 deg in order to provide National Weather Service forecasters with at least the same quality of data resolution that is currently available for making tornado and severe storm warnings.