Accuracy of Wind Fields in Convective and Stratiform Echoes Observed by a Bistatic Doppler Radar Network

A bistatic Doppler radar network is composed by one transmitting radar and one or more bistatic receivers with a non-scanning, passive antenna. The bistatic receiver is synchronized with sole transmitting radar by a GPS signal, and measures oblique scattering signals from target echoes. Three dimensional wind fields are synthesized by two or more Doppler velocities measured by the transmitting radar and the bistatic receivers. The bistatic Doppler network has begun to attract notice from various corners of the world, because it is easy and inexpensive to introduce. Some experimental results have shown the bistatic network can observe realistic wind fields that are equal in traditional monostatic dual-Doppler observation. However, there is not enough discussion of the mathematical accuracy for the explain of actual data.

In this study, the accuracy of wind fields derived from a bistatic Doppler network is investigated theoretically, and is evaluated using observation data in CASES 97. Based on a mathematical examination, the square root error of the synthesized horizontal wind vectors is less than three times of observed Doppler velocities within a range of 40 < beta < 140 degree. The minimum error appears at beta=100 degree where beta is an angle between transmitter-target and receiver-target. There is a little variance-error of synthesizing velocities observed by the bistatic Doppler network, because all Doppler velocities are measured from individual volumes simultaneously. While, a bistatic radar equation including the bistatic resolution volume, the polarization scattering angle, and the estimated bistatic antenna-pattern leads to the corrected bistatic reflectivity and the minimum detectable reflectivity. These results can help to eliminate sidelobe contamination. Finally, practical wind accuracy is investigated using both convective and stratiform echoes. In strong convective echoes, the sidelobe contamination is the prime cause of the wind error. In week stratiform echoes, the minimum detectable power dominates the wind accuracy.