A Monopulse System: Applications for Weather Radar Observations

Application of monopulse antennas to weather radar has the potential to provide greater details on the circulation and shear of wind fields at sub-beamwidth resolutions, which are very important for, e.g., tornado detection. For either the azimuthal or elevation plane, a monopulse system uses two identical beams, whose outputs are summed (even-mode) and subtracted (odd-mode). The antenna segments forming these beams are physically separated and the amplitude and phase of Doppler returns from these sub-apertures should show correlation. As a result, the radar reflectivity and Doppler velocity could be estimated at a sub-beamwidth resolution. The phased array radar of the National Weather Radar Testbed (NWRT) located at Norman Oklahoma provides an ideal platform for implementing and evaluating such a monopulse system and in performed related experiments.

A sophisticated radar simulator developed at the University of Oklahoma is modified to emulate the monopulse antenna system that is possible on the NWRT radar, with one transmitted beam and four spatially separated, quadrant-receivers. The emulator incorporates randomly distributed scatters which are advected to the times of radar pulses by time-dependent flows simulated by the ARPS model at up to 12.5 m spatial resolutions. The returns from these scatters are integrated over the radar sampling volumes using realistic beam patterns. Radar reflectivity is calculated from model simulated hydrometeors. Statistical analyses will be performed on the data simulated by the enhanced emulator in monopulse mode, using very-high-resolution ARPS output of several types of weather conditions.