A dual-pulse repetition frequency scheme for mitigating velocity ambiguities of the NOAA P-3 airborne Doppler radar

To mitigate some of the deleterious effects of the relatively small unambig uous Doppler velocity range (Nyquist interval) of airborne X-band Doppler r adars, a technique has been developed to extend this interval. This techniq ue, termed the batch mode dual-PRE (pulse repetition frequency) technique, utilizes two batches of pulses that are each averaged to produce two veloci ty estimates at each range bin, with each batch at a different sampling rat e. Comparison of the two velocity estimates produces a difference velocity that is used to dealias the second estimate within an extended Velocity ran ge that is larger than the Nyquist velocities of either of the two original samples. In this implementation, the choices of the two PRFs are restricte d to ratios of 3/2 or 4/3 of the lowest PRF. Due to the spread of the input Doppler spectrum and spatial displacement fr om one radial to the next, however, this batch-mode technique can produce p rocessor velocity dealiasing mistakes, particularly in high wind shear envi ronments. For PRFs less than about 2000 s(-1), processor mistakes can easil y exceed 10% of all data points. With higher PRFs using the 3/2 ratio, the number of processor mistakes decreases to a few percent of the total number of samples even when observing strong convective storms and mesoscale conv ective systems. Test results from convective storm environments are shown f rom the airborne Doppler radar operated on the National Oceanic and Atmosph eric Administration's P-3 instrumented aircraft for a variety of base PRFs and ratios to show the utility of this technique.