1. NEXRAD TAC Meeting August 22-24, 2000 Norman, OK AP Clutter Mitigation Scheme Cathy Kessinger Scott Ellis Joseph VanAndel http://www.atd.ucar.edu/rsf/NEXRAD/TAC_DQ_Aug00/index.html

2. August 23, 2000Cathy KessingerSlide 2 Ground clutter due to anomalous propagation degrades the performance of rainfall estimates from radar Currently, it must be detected by operators and clutter filters turned on manually Automation! ReflectivityRadial Velocity Reflectivity AP Clutter Reflectivity Precipitation

3. August 23, 2000Cathy KessingerSlide 3 AP Clutter Mitigation Scheme Improve quality of rainfall estimates 4 CCR’s have been approved Preliminary implementation of the AP clutter detection algorithm is underway at OSF Planned implementation for Open Build 2

4. August 23, 2000Cathy KessingerSlide 4 AP Clutter Mitigation Scheme Automatic clutter filter control Radar Echo Classifier –Uses fuzzy logic techniques (for details, see http://www.atd.ucar.edu/rsf/NEXRAD/index.html) –AP Detection Algorithm (APDA) –Precipitation Detection Algorithm (PDA) –Clear Air Detection Algorithm (CADA) –other algorithms, as needed Reflectivity compensation of clutter filter bias Tracking of clutter filtered regions

5. August 23, 2000Cathy KessingerSlide 5 Radar Echo Classifier Tim O’Bannon is implementing REC –AP clutter detection algorithm is first –Sharing NEXRAD data sets for testing –Working out methods of comparing results between NCAR and OSF

6. August 23, 2000Cathy KessingerSlide 6 Evaluation of REC Use statistical indices to measure performance of algorithms against “truth” –CSI, POD, FAR computed from 2x2 contingency table For NEXRAD cases, truth defined by human experts (subjective) For S-Pol cases, truth defined by Particle Identification algorithm (objective)

7. August 23, 2000Cathy KessingerSlide 7 Radar Echo Classifier Objective truth fields with S-Pol added –Truth derived from Particle Identification algorithm using multi-parameter fields as input –No human truthing –Improves algorithm optimization –Lower FAR realized for APDA for S-Pol cases Less improvement for NEXRAD cases (subjective truth) –Allows for real-time statistical evaluation

8. August 23, 2000Cathy KessingerSlide 8 Example of S-Pol “truth” 11 February 1999 AP, clear air & precipitation Truth: –green = AP –gold = precipitation –red = clear air ReflectivityRadial Velocity Spectrum WidthTruth

9. August 23, 2000Cathy KessingerSlide 9 Radar Echo Classifier Two reflectivity features added –Both computed over a local area –Matthias Steiner “spin” variable Reflectivity difference from gate to gate > threshold Difference > 0, spin > 0; Difference <0, spin <0 Percentage of maximum possible spin changes Sign =100 for “speckled” fields, 0 for pure gradients –Tim O’Bannon “sign” variable Reflectivity difference from gate to gate Accumulate + or -1 depending on sign of difference Sign=0 for “speckled” fields, +1 for pure gradients

10. August 23, 2000Cathy KessingerSlide 10 Radar Echo Classifier Evaluating APDA in non-Doppler region (430 km) –Using spin and sign with reflectivity “texture” and vertical difference in reflectivity –Membership functions are not optimized –KNQA movie loopKNQA movie loop

11. August 23, 2000Cathy KessingerSlide 11 Radar Echo Classifier New Python Environment for Radar Processing (PERP) –Better software development environment –Debugging nearly done –Implemented Radar Echo Classifier on S-Pol Web-based display of REC output ( http://www.atd.ucar.edu/rsf/STEPS/AP/index.html) Real-time operation during STEPS Continue development during IMPROV this winter

12. August 23, 2000Cathy KessingerSlide 12 Precipitation Detection Algorithm Clear Air Detection Algorithm Particle Identification (truth) AP Detection Algorithm Radial VelocityReflectivity Movie loop of June 19 Movie loop of June 22 S-Pol real-time display of REC output

13. August 23, 2000Cathy KessingerSlide 13 Radar Echo Classifier Development continuing on –Precipitation Detection Algorithm –Clear Air Detection Algorithm

14. August 23, 2000Cathy KessingerSlide 14 Reflectivity FY99 PDA Truth FY98 CPDA Precipitation Detection Algorithm S-Pol scan with convective and stratiform precipitation (gold), clutter (green) and clear air return (red) Note improved detection of all precipitation regions with PDA vs CPDA CPDA is very good at detecting noise

15. August 23, 2000Cathy KessingerSlide 15 CADATruth CADATruth Clear Air Detection Algorithm Results shown from two of the S-Pol cases CADA performs well at detecting the clear air and does not detect most of the clutter return Edges of precipitation echoes are falsely detected

16. August 23, 2000Cathy KessingerSlide 16 Summary Implementation of REC at OSF is primary emphasis Continuing to develop REC algorithms –Sea clutter algorithm next Next fiscal year NCAR will: –Add reflectivity compensation to PERP –Start development of automatic clutter filter control