Test of a Staggered PRT Scheme for the French Radar Network

Abstract

This paper describes the test of a staggered PRT scheme for the French radar network. The design of the staggered scheme has been done in the following context: 1) the scheme is meant to be implemented on existing C-band and S-band radars of the network, the PRF of which cannot, for technical reasons, be increased above their current values (300?400 Hz for C band and 250?300 Hz for S band); 2) the minimum expected Nyquist velocity should be around 30 m?s?1; and 3) the Doppler information will essentially be used to retrieve a VAD wind profile and for data assimilation by operational nonhydrostatic numerical prediction models. An operational C-band radar of the network, located in Trappes, near Paris, has been modified in order to allow Doppler processing and a dual-PRT staggered scheme with two low PRFs (PRF1=310 and PRF2=360 Hz corresponding to a ratio of 6/7) has been implemented. Two months of data (July?August 2003) have been analyzed. The performance of the scheme is assessed qualitatively and quantitatively through the computation of the error structure of the various velocities: velocity at PRF1, velocity at PRF2, and combined velocity. The sensitivity of the error structure on the signal-to-noise ratio is documented. A 7 km ? 7 km median filter is introduced to reduce dealiasing errors.