The UMass Mobile W-Band Doppler Radar: System Overview and Sample Observations

The Microwave Remote Sensing Laboratory (MIRSL) at the University of Massachusetts has maintained and operated a mobile W-band Polarimetric Doppler Radar since the early 1990s. This radar has been a focal point of ongoing collaboration between UMass and the University of Oklahoma School of Meteorology in studies of severe thunderstorms and tornadoes using mobile radars. Over the past two years, the W-band radar has undergone a major rebuild and upgrade. Modifications include a new modulator for the klystron transmitter and associated redesign to accommodate the same, a new control and data acquisition system based on FPGA and digital receiver technology, real-time display, and new mechanical packaging, and conversion of the entire system to battery power recharged by the truck's engine, eliminating the need for a generator.

Due to the 3 mm wavelength, the unambiguous velocity interval for W-band radars is very narrow. A limitation of the prior data acquisition system was a single pulse-pair interval requiring use of polarization-diverse pulse-pair methods to obtain unwrapped velocities in high-wind events. The new system relieves this constraint allowing dual- or multiple-PRT methods to obtain unwrapped velocities. Real-time full spectrum (FFT) processing is in development. This paper documents the upgraded system and shows selected results from recent deployments.