Weather Radar Signal Processing and Recording at the National Severe Storms Laboratory

Abstract

The radar data system at the National Severe Storms Laboratory presents weather radar return power data with a significant reduction in the variations that arise from the relative motion of discrete precipitation elements. The system provides intensity-contoured plan position indicator (PPI) displays for visual inspection and photographic archival, and digital records in azimuth-range coordinates for use in computers and for narrow-band transmission to remote locations. Digital records can also be reproduced in the PPI format. The spatial distribution of echo power perceived during each two degrees of antenna azimuthal revolution, is represented as ten levels of return power intensity at intervals of 2°×1 nmi. Spatial reticulation is of the same order as limits of resolution inherent in the radar beamwidth and pulse length, and the system output thus retains most of the information on precipitation rate distributions contained in the unprocessed video signals. Averaging over two pulse lengths and the equivalence of ten pulse periods provides approximately Gaussian-distributed estimates of mean intensity with a standard error of 1 dB, less than one-fifth of the uncertainty of point-sampled unprocessed video. The system is used routinely at NSSL with a 10-cm WSR-57 radar, a type widely used by the Weather Bureau, and could be adapted to any weather radar system.