A New Inanimate Class for the WSR-88D Hydrometeor Classification Algorithm

The current implementation of the Hydrometeor Classification Algorithm (HCA) on the WSR-88D contains two non-hydrometeor-based classes: ground clutter/anomalous propagation and biological scatterers. However, numerous other non-hydrometeor targets that do not fall into these two categories can be encountered by the radar, including chaff, sea clutter, combustion debris, and radio frequency interference. The HCA always provides a classification so these targets often masquerade as one of the non-hydrometeor classes, but can also appear as meteorological targets. In order to address this discrepancy, a new class (nominally named “inanimate”) has been developed that encompasses many of these non-meteorological targets. Using this class, a distinction between non-biological and biological non-hydrometeor targets can be made. A discussion regarding the fuzzy logic membership functions, optimization of membership weights, and class restrictions is presented, with a focus on observations of highly stochastic differential phase estimates in all of the aforementioned targets. Numerous examples of non-hydrometeor cases with the new HCA class are shown, with before-and-after comparisons. Attempts to separate the results into sub-classes using a support vector machine are presented, and examples of each target type are detailed. Considerations concerning eventual implementation into the WSR-88D radar product generator are addressed.