An Inexpensive, Mobile, Rapid-Scan Radar

There is a compelling need for more rapidly updated radar data in a variety of phenomena.

DOW mobile radar data have revealed that substantial changes occur in the reflectivity and velocity fields of tornadoes in less than 60 s. Small-scale structures recently observed in landfalling hurricanes evolve with time scales of much less than 60 s. Microbursts have been observed to change on time scales of less than 100 s. In order to understand the evolution of these phenomena, volumetric radar data with update rates of << 60 s are required.

Phased array radar systems can obtain data with these update rates. Unfortunately, they are extremely expensive and are unlikely to be commonly available to the meteorological community as operational or research tools.

A new rapid-scan-DOW has been designed and is under construction at the University of Oklahoma and the National Center for Atmospheric Research. This radar employs multiple simultaneously (or nearly so) transmitted beams, each at a slightly different frequency. These beams are transmitted through a single slotted waveguide antenna that is designed to maximize frequency steering. Returned echoes are received simultaneously through the same antenna, and processed semi-independently in real-time to produce reflectivity and Doppler data at several elevation angles. The antenna is scanned mechanically in the azimuthal direction, then stepped coarsely through elevation, resulting in 10 tilt volume scans in 12 s. Beam-by-beam dithering of the frequencies can produce a sawtooth scanning pattern, eliminating the azimuthal-resolution vs elevation-resolution mismatch that is commonly present in scanning radars.

The rapid-DOW should be operational starting in 2002-3 and costs less than 10% of a comparable phased array system.