week, and increase the spatial resolution of surface observations by expanding from 250 to almost 1,000 airports around the country. The network was intended to automate the observation and dissemination of temperature, dew point, visibility, wind direction, wind speed, barometric pressure, cloud height and amount, and the type and amount of precipitation. The goal was acquisition of spatially and temporally uniform measurements, continuous observation and reporting, and more observing sites nationwide.

Radar

The NWS weather radar system in the 1980s comprised some fifty-odd WSR-57 and WSR-74S (Weather Surveillance Radar) S-band “network” radars and nearly seventy WSR-74C C-band “local warning” radars. These radars displayed the storm echo patterns and measured radar reflectivity, related to storm intensity, in a semi-quantitative manner. Coverage at mid-levels for the atmosphere was fairly broad east of the Rockies, but only spotty farther west. The WSR-57s in particular were aging and becoming difficult and expensive to maintain. Thus the need for a replacement system in the not too distant future was becoming pronounced.

Fortunately, the development of the Next Generation Weather Radar (NEXRAD) was well under way long before the nominal beginning of the MAR. Early work using 3.2 cm (X-band) wavelength short-range continuous-wave (CW) Doppler radar technology had demonstrated capability to detect tornadic wind speeds (Smith and Holmes, 1961) in addition to measuring reflectivity. However, that system was limited by inability to determine range to the target and by problems with loss of signal intensity in conditions involving precipitation. For routine operational applications, the development of pulse-Doppler technology for long-range weather radar (at longer wavelengths less subject to attenuation) was needed to furnish both range and velocity information (Whiton et al., 1998). Improvements in data processing and display technology were also needed to present the information in usable formats.

Work on the pulse-Doppler technology also began around the late-1950s (Rogers, 1990), first under U.S. Air Force (USAF) auspices and later at the National Severe Storms Laboratory (NSSL). By the late 1960s it was evident that the technology could reveal storm signatures of potential value in forecast and warning applications (Donaldson et al., 1969); a tornado vortex signature was identified in the echoes from a 1973 Oklahoma storm (Burgess et al., 1975). However, it took the introduction of real-time computing and the development of color display technology in the early 1970s to provide a means for bringing the data from a single Doppler radar to meteorologists in a conveniently usable fashion.

In the mid-1970s the NWS jointly teamed with the DOD and the Department of Transportation (DOT) in anticipation of the need to replace the WSR-57, WSR-74, and FPS-77 radars deployed over the preceding 20 years, to form the Joint Doppler Operational Project (JDOP; Whiton et al., 1998). The experiments and tests performed at NSSL and by the NWS and USAF Air Weather Service in 1976 and 1977 showed that Doppler radar provided much earlier detection of severe and tornadic storms, and could also detect gust fronts that might present a hazard to flight operations at airports.

On the basis of the successful JDOP demonstration of the potential value of Doppler radar to the missions of the NWS, the USAF, and the FAA, development of the NEXRAD system got under way in earnest in 1979: the Office of the Federal Coordinator for Meteorological Services and Supporting Research (OFCM) approved a NEXRAD concept document and established a tri-agency NEXRAD Program Council (NPC); the NPC approved formation of a Radar Test and Development Branch (later to become the Interim Operational Test Facility, then the Operational Support Facility, and eventually the Radar Operations Center); and the Office of Management and Budget (OMB) directed the OFCM to conduct a tri-agency cross-cut study for NEXRAD. Finally, NOAA approved establishment of a NEXRAD Joint System Program Office (JSPO) to move forward with the development, contract award, and deployment of a NEXRAD network. An NRC report (NRC, 1980) added momentum to the effort to implement an operational Doppler weather radar capability. The NPC formed a NEXRAD Technical Advisory Committee in 1980 to provide recommendations on newly-developed capabilities that are ready for implementation as well as engineering and scien-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement