ABSTRACT
Radar was invented in the 1930s and has been used extensively for air traffic surveillance and control. Beginning in the late 1940s, it was determined that radar could also be useful for detecting and measuring precipitation. Since then, radar has become the preferred technology to detect and track severe weather. More recently, Doppler capability has been added to many weather radar systems to permit measuring the wind velocity associated with the precipitation. The U.S. National Weather Service (NWS) has upgraded the U.S. National Weather Radar network to WSR-88D (NEXRAD) radar systems. WSR-88D is sophisticated, fully coherent Doppler weather radar with true threedimensional volume scanning and processing capability. The U.S. Federal Aviation Administration (FAA) has installed Terminal Doppler Weather Radar (TDWR) systems at selected airports in the United States. TDWR is also a sophisticated, fully coherent Doppler radar system whose primary function is to detect low-level wind shear in the approach and departure flight path of an airport runway. Low-level wind shear has proven to be extremely hazardous to aircraft during takeoff and landing. Dual-polarization technology is now being introduced that provides increased accuracy of precipitation information.
