Detection and removal of radar data contaminated with return from anomalously propagated (AP) ground clutter is a serious data quality issue for the NEXRAD WSR-88D. Normally propagated (NP) ground clutter from stationary targets is removed as part of the WSR-88D data quality system. Improved precipitation estimates from radar are achieved with the removal of AP and NP ground clutter. In cooperation with the Operational Support Facility (OSF), NCAR has developed a detection algorithm for AP contamination for the WSR-88D. This algorithm uses a fuzzy logic classifier on the Archive 2 (A2) data stream to identify AP and NP ground clutter. NCAR has also developed a time-series data recorder, the A1DA, specifically for the WSR-88D systems. The A1DA can be attached to the WSR-88D data aquisition unit to record time-series data.
Using the A1DA, time-series radar data were collected from the Memphis WSR-88D during July 1997. These data were collected over a two week period with the intent of capturing AP clutter events. Several episodes of AP clutter occurred with and without accompanying precipitation radar return. Using the time-series data, contamination from AP clutter and stationary ground targets is identified. Using the identified regions of ground clutter as "ground truth", the data are input into the AP detection algorithm and its performance assessed. The advantage of this technique is that the determination of ground truth is done before the A2 processing. A ground clutter filter, similar to those used in the WSR-88D, will be applied to the data set to examine the algorithm performance on a "before and after" basis.
These time-series data provide an important means for examining various methods of improving data quality for the WSR-88D. With the advent of the Open RDA signal processing system, real-time implementation of algorithms that detect and remove AP and stationary ground clutter may be realized using the time-series data as input rather than the A2 data. This paper is a first attempt at examining this type of algorithm.