Staggered Pulse Repetition Time Clutter Filter (‘SACHI’) Performance

1. Staggered Pulse Repetition TimeClutter Filter (‘SACHI’) Performance Data Quality Technical Interchange Meeting November 19-20, 2008 David Warde and Sebastián Torres, CIMMS, University of Oklahoma NSSL/OAR/NOAA, Norman, Oklahoma DQ TIM Fall 2008

2. Outline • TAC Brief • Interlaced with some things I didn’t show at the TAC DQ TIM Fall 2008

3. History • SACHI Filter • NSSL Report 3, 1999 • Described Algorithm • Provided Preliminary Filter Performance • NSSL Report 9, 2005 • Provided Algorithm Description • Used Table • NCAR Report, 2007 • Analyzed Filter Performance – Fixed Notch • NSSL Report 11, 2007 • Improved Algorithm Description • Adaptable Notch Based on GMAP • NSSL Report 12 (Pending Release) • Performance Evaluation DQ TIM Fall 2008

4. Clutter Filtering System Specifications • System Specification (SS) Performance Requirements Anticipate IIR Filter • Apply to Lowest Two Elevation Cuts of Scan Strategies 1 (VCP11) and 2 (VCP21) • Testing Set-up • SNR = 20 dB • CSR ≥ -30 dB • Spectrum Width (σv): 4 m/s • Velocity: Extent of Nyquist DQ TIM Fall 2008

5. Clutter Filtering System Specifications(Continued) • Reflectivity • Clutter Suppression: 30 dB • Bias: (measured @ SNR 20 dB, CSR -30 dB) DQ TIM Fall 2008

6. ‘SACHI’ Filter Performance • Clutter Suppression for Reflectivity (Goal 30 dB) ~10 Clutter Suppression ~50 Clutter Suppression DQ TIM Fall 2008

7. PRT = Performance Dwell = Performance ‘SACHI’ Filter Performance(Continued) VCP212 12.0° 16.7° 10.0° 19.5° 8.0° 6.4° 882 1002 1125 1248 1371 1494 1617 1740 2000 5.1° 4.0° 3.1° 2.4° 1.8° 1.3° 0.9° 0.5° SZ2 10 50 DQ TIM Fall 2008

8. ‘SACHI’ Filter Performance(Continued) • Reflectivity Bias – Surveillance (Non-Operational Test) DQ TIM Fall 2008

9. ‘SACHI’ Filter Performance(Continued) • Reflectivity Bias – Doppler (Operational Test) DQ TIM Fall 2008

10. ‘SACHI’ Filter Performance(Continued) • Reflectivity Bias – Clear Air (Non-Operational Test) DQ TIM Fall 2008

11. Clutter Filtering System Specifications(Continued) • Velocity and Spectrum Width • Clutter Suppression: 20 to 50 dB • Bias and Standard Deviation: • 2 m/s for Usable Velocities @ 20 dB SNR, -30dB CSR, σv of 4 m/s +2 -2 20 Legacy Low Legacy Medium Legacy High DQ TIM Fall 2008

12. ‘SACHI’ Filter Performance(Continued) • Velocity Bias • Goal - 2 m/s Bias • Usable velocities 4 m/s @ 50 dB, 3 m/s @ 28 dB, 2 m/s @ 20 dB DQ TIM Fall 2008

13. Velocity Dealiasing PRT = 1740 us SNR = 20 dB CSR = 40 dB SW = 4 m/s DQ TIM Fall 2008

14. Velocity Dealiasing (cont) PRT = 882 us SNR = 20 dB CSR = 40 dB SW = 4 m/s DQ TIM Fall 2008

15. 2/5 Nyquist 4/5 Nyquist 0 Nyquist What’s Happening? • Recall SPRT 2:3 Code [1 0 1 0 0] DQ TIM Fall 2008

16. ‘SACHI’ Filter Performance(Continued) • Velocity Bias and Standard Deviation S PRT = 2000 μs Dwell = 54 ms PRT = 1002 μs Dwell = 64 ms D C PRT = 1494 μs Dwell = 82 ms DQ TIM Fall 2008

17. ‘SACHI’ Filter Performance(Continued) RPG VDA May Allow Longer PRTs And/Or Shorter Dwell Times 40 DQ TIM Fall 2008

18. ‘SACHI’ Filter Performance(Continued) • Spectrum Width Bias and Standard Deviation – Goal - 2 m/s T1 882 μs, Dwell 60 ms T1 1740 μs, Dwell 40 ms DQ TIM Fall 2008

19. ‘SACHI’ Filter Performance(Continued) DQ TIM Fall 2008

20. Summary • Performance of ‘SACHI’ filter comparable with GMAP filter in WSR-88D • Clutter Suppression 30 to 50 dB • WSR-88D System Specification met for Reflectivity, Velocity, Spectrum Width • Depending PRT/Dwell Time Selection • Velocity main constraint • Velocity dealiasing at RPG (va/2) • Ready for Phase III • ROC implementation into WSR-88D • ROC Data Quality Assessment DQ TIM Fall 2008

21. Questions? DQ TIM Fall 2008