In the spring of 2008 the Radar Operations Center (ROC) plans to upgrade an operational WSR-88D volume coverage pattern (VCP 121). The upgrade reduces range aliasing by combining the Sachidananda-Zrnic phase coding algorithm (designated SZ-2) with a multi-scan algorithm called the Multiple Pulse Repetition Frequency (PRF) Dealiasing Algorithm (MPDA). The MPDA, fielded in 2004, combines velocity data from up to three sweeps at the same elevation angle but with different PRFs. Velocity data that is aliased using one PRF may not be range aliased using another PRF. The SZ-2 algorithm separates weak trip echo from strong trip echo by encoding successive pulses through a defined sequence of phase shifts to reduce range aliasing. The MPDA frequently leaves range aliased data beyond 175 km. The SZ-2 algorithm performs well at long range but has residual range aliased data at the start of its second trip echo. Thus, when combined, the two techniques complement each other.

Four data cases with widespread precipitation were collected on the ROC's test bed WSR-88D during the fall and winter of 2006. Analysis of the data indicates velocity recovery of 98 percent (by area) out to a range of 230 km is possible by combining the techniques. Use of SZ-2 by itself provides velocity recovery of nearly 92 percent of the data field. Use of the MPDA alone recovers 65 to 70 percent. A field test is being conducted during the latter half of calendar year 2007 at eight field sites to validate the performance under meteorologically and geographically diverse conditions.