Atmospheric conditions favorable for refraction of the radar beam can produce additional ground clutter return, called anomaluosly propogated (AP) ground clutter return. The AP clutter return is a serious data quality problem for the WSR-88D because it causes erroneous radar-derived rainfall estimates as well as other algorithmic errors. Currently, the WSR-88D quality control system removes AP clutter through the manual application of ground clutter filters. The AP Clutter Mitigation Scheme is being implemented within the Open Radar Product Generator (ORPG) with the goal of automating the clutter-filtering processes. The first WSR-88D implementation of the AP Clutter Mitigation Scheme occurred in September 2002 with the deployment of the AP clutter detection algorithm (APDA) during build 2 of the ORPG. The AP Clutter Mitigation Scheme consists of four parts: the radar echo classifier (REC)of which the APDA is one part, the reflectivity compensation scheme (Z-Comp), the augmentation of the clutter bypass map and the specification and control of the ground clutter filters.

The radar echo classifier (REC) uses fuzzy logic techniques to determine the type of scatterer measured by the WSR-88D. Currently, four algorithms reside within the REC: the APDA determines AP ground clutter return, the precipitation detection algorithm (PDA) defines regions of convective and stratiform precipitation, the insect clear air return algorithm (ICADA) defines return from insects in the boundary layer, and the newest algorithm is the sea clutter detection algorithm (SCDA). The first three algorithms have been developed on WSR-88D data and on data from the NCAR S-Pol polarimetric radar. The SCDA has been tested and deployed on the United Arab Emirates (UAE) Doppler radars and will soon be tested on WSR-88D and S-Pol radars. Real-time deployment of the REC on the S-Pol has been accomplished at various field experiments since June 2000. Results will be presented.

The reflectivity compensation scheme (Z-Comp) estimates the correction necessary to offset the clutter filter induced bias in the reflectivity. This method has been extended to the radial velocity and spectrum width fields as well. For the AP Clutter Mitigation Scheme, output from the APDA and the PDA determine where the Z-Comp algorithm is applied such that only precipitation regions are compensated. The Z-Comp methodology has been tested with WSR-88D time series data and during field operations of the S-Pol radar since 2001. Results will be presented.

Plans for automation of the clutter filtering processes will be presented.