In the NEXRAD network, the range and Doppler velocity ambiguity problems are coupled such that trying to alleviate one worsens the other. Operationally, this is evidenced by the obscuration of overlaid weather echoes and/or the aliasing of measured Doppler velocities, both of which impair the effective observation of weather phenomena. Identified as one of the highest technical needs for the NEXRAD program, the Radar Operations Center of the National Weather Service has sponsored the National Severe Storms Laboratory (NSSL) to develop signal processing methods for mitigating the effects of velocity and range ambiguities on the US weather radar network. The first stage of this development was completed during 2007 with the operational deployment of a technique based on systematic phase coding termed as SZ-2. However, SZ-2 was designed to run only at the lower antenna elevation angles. Recently, NSSL recommended a staggered pulse repetition time (SPRT) algorithm for the second stage of deployment. This algorithm is based on a transmission sequence with two alternating PRTs and is suggested for intermediate to higher elevation angles of the antenna beam.

Comparisons with existing “legacy” algorithms have demonstrated the ability of SPRT to effectively mitigate range and velocity ambiguities. However, the performance of this algorithm is limited by the accuracy of Doppler velocity estimates obtained for each PRT set. Large errors of estimates lead to dealiasing errors that cannot be effectively mitigated by the existing velocity dealiasing algorithm (VDA). This paper describes the status and plans for the operational deployment of the staggered PRT algorithm, the performance of the algorithm in terms of velocity dealiasing errors, and a modification to the current VDA to mitigate this particular class of errors.