Describes the development and first operation of a innovative research tool for observing atmospheric storms: an airborne X-band Doppler radar. The radar has been built jointly by the National Center for Atmospheric Research (NCAR) in Boulder, CO and the Centre de Recherches en Physique de l'Environnement Terrestre et Planetaire (CRPE) in Paris, France. The radar is called ELDORA/ASTRAIA for Electra Doppler Radar/Analyse Stereoscopique par Radar Aeroporte sur Electra. The radar is designed to provide high-resolution measurements of the air motion and rainfall characteristics of very large storms: storms which are frequently too large and/or too remote to be adequately observed by ground-based radars. This paper includes discussions of the scientific impetus and design criteria as well as the engineering solutions to these design needs. The design options and tradeoffs of the resulting capabilities are discussed. The paper concludes with an evaluation of the performance of the system at its first field test, conducted as a part of the international global warming experiment in the equatorial Pacific Ocean known as the Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE). This evaluation illustrates that the major design goals for the radar - collection of relatively noise-free velocity and reflectivity data using a rapid scanning radar - have been adequately met. Future options for further improvements to the radar are discussed.>

A bistatic dual-Doppler network consisting of an existing single transmitting pencil-beam weather radar and a remotely located, nontransmitting, passive bistatic receiver with a low-gain antenna was constructed and tested during 1993. High-quality dual Doppler vector winds were retrieved from this system. The windfields were compared with those collected with a traditional two-transmitter dual-Doppler system. Several interesting engineering challenges relating to frequency and timing synchronization were resolved in order to retrieve successfully Doppler velocities at a remote bistatic site. Frequency synchronization was achieved by using extremely stable local oscillators, linked by both Global Positioning Satellite (GPS) signals and transmitter sidelobe coupling. Both methods provided the necessary one part in 10/sup 9/ coherence necessary for calculating accurate Doppler velocities. Timing/gating synchronization with submicrosecond accuracy was achieved by using local oscillators at each site linked with GPS and sidelobe coupling. The successful testing of this system demonstrates that inexpensive and practical bistatic multiple-Doppler networks can be deployed. These systems can provide three-dimensional vector winds for a number of purposes in research, aviation, media, weather prediction, education, meteorological modeling and severe weather detection.>