Waveform Design Applications for Observations of Severe Local Storms and Tornadoes

In order to provide adequate sensitivity in low-power radar systems, pulse compression has been used for decades in military applications, and more recently, weather radar. Over the past two years, the Advanced Radar Research Center at the University of Oklahoma has been developing novel waveform design techniques for weather radar platforms which provide excellent sidelobe performance while maintaining power efficiencies as high as 95%. Such waveforms are capable of dramatically lowering price points on all types of radar systems, including both phased array and dish-type platforms. These waveforms have been implemented on the PX-1000 transportable, solid-state, polarimetric X-band dish radar, which operates at 100 Watts on each channel, as well as the Atmospheric Imaging Radar, a mobile X-band tornado-scale imaging system with a 20-degree vertically distributed 3.5 kW TWT fan beam on transmit and a phased array capable of digital beamforming on receive. Due to low transmit powers, both platforms require the use of long-pulse waveforms in order to achieve acceptable sensitivity. Both systems observed significant tornadoes and numerous severe local storms in 2013, including the 20 May Moore, Oklahoma EF-5 tornado, as well as the 31 May El Reno, Oklahoma EF-3 tornado. Data from both of these cases is presented, including high-temporal resolution animations of the evolution of multiple tornadoes, sharp cutoff reflectivity images in squall line and hail cases, polarimetric data with multi-lag processing from PX-1000, and discussion regarding both the effects from Doppler tolerance in tornadoes, as well as challenges surrounding waveform design in imaging and phased array systems.