An algorithm to detect anomalously-propagated (AP) ground clutter contamination within the WSR-88D base data fields has been under development for several years. This work is being done with the cooperation of the WSR-88D Operational Support Facility (OSF) and the National Center for Atmospheric Research (NCAR). Detection of AP contamination will augment the detection of ground clutter from stationary targets that is a part of the WSR-88D system. This augmentation is necessary since AP contamination varies depending on atmosperic conditions. This algorithm is planned to be a pre-processor of the WSR-88D base data fields prior to input into the Precipitation Processing System (PPS).
Initially, three techniques were selected for evaluation of potential usefulness in detecting anomalously-propagated ground clutter contamination (Keeler et al, 1998). These techniques were: a neural network scheme, a fuzzy logic classifier and an empircal, rule-based technique. After testing the techniques, the fuzzy logic classifier was selected as the algorithm of choice. Reasons for this selection include the ease of implementation and the small differences in statistical performance between the fuzzy logic classifier and the neural network classifier.
Using the fuzzy logic classifier, the AP detection algorithm has been further developed to better define and optimize the piece-wise linear membership functions for each input variable. Selected cases from the WSR-88D archives have been input into the algorithm. A human "expert" defines the regions of AP contamination (i.e., the "truth" regions) by drawing polygons. These "truth" regions are used to statistically score algorithm performance. Results from the final optimization of the fuzzy logic classifier will be presented.
Reference:
Keeler, R.J., F. Pratte, D. Ecoff, J. VanAndel, and D. Ferraro, 1998: NEXRAD anomalously propagated ground clutter mitigation. Preprints, 14th International Conference on Interactive Information Processing Systems (IIPS) for Meteorology, Hydrology and Oceanography, American Meterological Society, Phoenix, AZ, 11-16 January 1998.