Implementation of the AP Clutter Mitigation Scheme is underway within the WSR-88D system as part of the Open Radar Product Generator (ORPG). Once fully implemented, this scheme will improve the radar base data quality by identification and removal of ground clutter produced under anomalous propagation (AP) conditions. The WSR-88D quality control system removes ground clutter that is present during normal propagation conditions by application of clutter bypass maps. AP ground clutter requires manual application of additional clutter filters. The AP Clutter Mitigation Scheme is working toward full automation of ground clutter filter specification and control. The first step in this implementation was achieved when the AP Clutter Detection Algorithm (APDA) was deployed during Build 2 of the ORPG in September 2002. Output from the APDA is available for perusal on the ORPG Clutter Filter Control panel.

The AP Clutter Mitigation Scheme consists of three parts: the Radar Echo Classifier (REC) of which the APDA is one module, the Reflectivity Compensation Scheme (Z-Comp), and clutter filter specification and control. The Radar Echo Classifier (REC) is a data fusion system that uses fuzzy-logic techniques to estimate the type of scatterer measured by the WSR-88D. The REC consists of three algorithms: the APDA classifies AP ground clutter return, the Precipitation Detection Algorithm (PDA) classifies precipitation regions, and the Sea Clutter Detection Algorithm (SCDA) classifies return from the ocean surface. The Reflectivity Compensation Scheme (Z-Comp) uses a Gaussian approximation for precipitation spectra and a simulated WSR-88D clutter filter to estimate the correction necessary to offset the clutter-filter-induced bias in the reflectivity. Output from the PDA determines where the Z-Comp method is applied such that only regions of precipitation are compensated.

The Sigmet Corporation RVP8 digital signal processor will be installed on the WSR-88D systems as the Open Radar Data Aquisition (ORDA). The RVP8 has also been installed on the NCAR S-Pol radar as a parallel processor. The RVP8 processor will allow the use of spectral domain processing and will facilitate greater improvement in base data quality. Modification of the AP Clutter Mitigation Scheme to accomodate the new ORDA processor is planned and will be presented.