Abstract
Most severe convective storms are too remote, occur too infrequently, or translate too rapidly to be resolved at high enough spatial and temporal scales by fixed-site, ground-based radars. Fortunately, the recent introduction of mobile radar platforms into the field has had a major impact on advancing our understanding of the internal structure of severe convection. These systems can be broadly divided into airborne, spaceborne, and ground-based mobile platforms. The National Oceanic and Atmospheric Administration (NOAA) P-3, Electra Doppler Radar (ELDORA) ER-2 Doppler Radar (EDOP) are examples of aircraft equipped with radars that have successfully collected data on supercell storms, tornadoes, microbursts, and intense squall lines. Spaceborne platforms might be considered of limited use for studying severe convective storms owing to their high altitude, poor temporal resolution over a particular geographic region, and narrow swath with respect to the earth. However, an example of a synthetic-aperture radar detecting microbursts over the ocean and the ability of the Tropical Rainfall Measuring Mission (TRMM) radar to provide the first global data of severe convective storms are discussed.
Ground-based radars have been used to map the wind field near and within severe convective features close to the ground at very high update cycles. Doppler spectra in tornadoes suggesting F5 wind speeds were collected by a continuous wave radar developed by the Los Alamos National Laboratory. The University of Massachusetts—Amherst built a W-band radar that was mounted in a van and later a truck. This radar was designed with a beamwidth of 0.18°, allowing for ultrahigh spatial resolution. Moreover, a polarization diversity pulse-pair technique was implemented so that the maximum unambiguous Doppler velocity was large enough to be useful in determining maximum wind speeds in tornadoes. The University of Massachusetts radar and an X-band system, developed jointly by the University of Oklahoma, the National Severe Storms Laboratory, and the National Center for Atmospheric Research and also mounted on a truck, known as the Doppler on Wheels (DOW), have collected unprecedented data on the finescale structure of tornadoes. “Eyes” and spiral bands in the radar reflectivity fields were shown to be ubiquitous. For the first time, data suggesting the existence of multiple vortices within tornadoes have been collected.
There has been a burgeoning growth of mobile radar systems that continues to this day. Two C-band systems have been built and are in the early stages of being tested. These two systems known as the Shared Mobile Research and Teaching Radars (SMART-Rs) and the Seminole hurricane hunter are both equipped with polarization diversity. These radars will be able to provide more details of the precipitation physics within severe storms and the range and velocity ambiguities will be reduced. A DOW radar capable of rapid scanning is under development by the University of Oklahoma and an X-band phased array is being converted for meteorological use by the University of Massachusetts. Other examples are provided.
