An automatic Anomalous Propagation (AP) clutter detection and suppression algorithm based on Fuzzy Logic has been developed at NCAR. Because AP clutter is a space and time variable field that contaminates the precipitation measurements, we have developed a technique that adapts to the changing propagation characteristics of the boundary layer at every volume scan.
The AP clutter is first detected, then suppressed with standard clutter filters automatically applied as described. As the AP clutter field changes, the filter application is also changed to accommodate it. A radar reflectivity compensation scheme will correct precipitation estimates that are typically biased low by the clutter filters in the present Nexrad.
We plan a 2 stage implementation, first in the Open RPG with a sub-optimal detection and compensation algorithm being implemented in the RPG software with automatic enhancement of the clutter filter (Bypass) map being made to the system controller. The conservative and enhanced clutter sector map can be applied after each volume scan after approval (or rejection) by the radar operator as desired. The detected AP areas will be flagged for ingest into the Precipitation Preprocessing Subsystem (PPS) algorithm or any other algorithm. Later when the Open RDA allows additional RDA processing and access to both the filtered and unfiltered Archive 2 base data streams, a more complete algorithm can be implemented. The Open RDA processor system should have sufficient power for Doppler spectral processing which may yield higher performance than base data processing alone.