Jane Krause, Amy Daniel and Brandon Taylor along with ROC employees Rich Ice and Dave Zittel, prepared and a presented a poster session entitled: “Evaluation of Clutter Residue Censoring on the WSR-88D Radar System” WSR-88D radar sites with mountainous terrain in their vicinity have had a significant amount of clutter residue in their meteorological data.
A data recorder was sent to the Pueblo, CO (KPUX) radar site in order to collect Level I data with which to provide mountainous terrain data that was previously unavailable for analysis. The current thresholds for the dB-for-dB additional suppression were analyzed for performance, and other more aggressive settings were evaluated both on an individual volume basis and for long term analysis for precipitation accumulations. It was determined that adjusting the upper dB-for-dB threshold downward by 5 dB will sufficiently remove clutter residue without degrading precipitation accumulation algorithm performance.
Lindsey Richardson, along with ROC employees Rich Ice, Dave Zittel, Bob Lee and Deutscher Wetterdienst (German National Weather Agency) employees Michael Frech and Jorg Seltmann cooperatively developed a poster entitled: “Monitoring Radar System ZDR Accuracy: S and C band Operational Experiences in the US an Germany”
The US and German weather radar networks are using scans of external targets to estimate radar system bias in support of Differential Reflectivity (ZDR) calibration. While the C-Band German radars can use vertical scanning in rain to measure bias, the US S-Band WSR-88D system is limited to 360 degree azimuthal scans below 20 degrees elevation. The US system uses these operational volume scans to find regions containing suitable scatterers, (e.g., light rain below the melting layer, dry snow above the melting layer, and Bragg scatter in clear air) and compares the return with expected intrinsic ZDR values.
The German system employs purposeful vertical scans on a frequent basis, taking advantage of the symmetry of scattering principle that the mean ZDR in light rain with a vertical scan should be zero. The statistics of returns, including bias and variability, need to be understood in order for scans of hydrometeors to be used for accurate bias estimation. Comparisons of vertical and non-vertical incidence scanning methods may prove useful in pursuit of these statistics. The US and German radars both employ daily sunspike monitoring to assess ZDR bias and to monitor antenna position accuracy.
This paper reviews efforts from both countries related to the utility and variability (including seasonal and geographical availability) of these methods for the S-band WSR-88D and the German C-band polarimetric radars. The relevance of the external methods for diagnosing hardware problems will also be discussed.