Dual Polarization Technology: The KICT Upgrade

1. Dual Polarization Technology:The KICT Upgrade Paul Schlatter Warning Decision Training Branch

2. Outline Explain dual-pol and the new products What dual-pol can/can’t do Current training and deployment plans

3. The WSR-88D Prior to Dual-pol Upgrade 88D • Traditional radars transmit and receive each pulse with the E-field parallel to the local horizontal surface. _

4. WSR-88D with the Upgrade to Dual-Pol • Transmitted at 45o, received at both horizontal and vertical

5. Compare to Current WSR-88D Policy of “Do no harm” Retrofit on existing dish, tower, etc. Same VCPs, wavelength, beamwidth Velocity, SW, Reflectivity, Algorithms: Unchanged

6. List of New Products via Dual-Pol • Correlation Coefficient (CC) • Differential Reflectivity (ZDR) • Specific Differential Phase (KDP) • 2 Algorithms • Melting Layer • Hydrometeor Classification • 9 NEW Precipitation Estimation Products

7. The Dual-Pol Base Products

8. New Base Product #1 Correlation Coefficient (CC) N

9. Physical Interpretation

10. Correlation Coefficient (CC) Typical Values

11. What is CC Used for? • Not-weather targets (LOW CC < 0.80) • Best discriminator • Melting layer detection (Ring of reduced CC ~ 0.80 – 0.95) • Giant hail or tornadic debris (LOW CC < 0.70 in the midst of high Z/Low ZDR)

12. Marginally Severe Supercell Rain What about the rest? All > 0.97 Precip Insects

13. Melting Layer Example 3. Melting Layer Detection Frozen Mixed Phase Liquid 2.4 deg CC

14. New Base Product #2: Differential Reflectivity (ZDR) Horizontal Reflectivity Vertical Reflectivity

15. Physical Interpretation Pv Pv Pv Ph Ph Ph Zh ~ Zv Zh > Zv Zh < Zv

16. Why Would You Examine ZDR? • Severe-sized hail or hail shafts without a lot of liquid water Indicates the presence of liquid drops

17. Typical ZDR Values for Various Targets

18. Marginally Severe Supercell

19. Definition:gradient of the difference between phase shift in the horizontal and vertical directions Units:degrees per kilometer (o/km) New Base Product #3: Specific Differential Phase Shift (KDP) Differential phase shift

20. Differential Phase Ilustrated • blah

21. Forward Propagation has its Advantages Gradients Most Important= KDP!!! Immune to partial (< 40%) beam blockage, attenuation, radar calibration, presence of hail Used primarily for rainfall estimation

22. Typical Values of Specific Differential Phase Shift (KDP)

23. Marginally Severe Supercell

24. Base Data Summary Need to integrate at a minimum Z, ZDR, and CC to analyze the situation AWIPS is ready Are humans???

25. The Dual-Pol AlgorithmsQPE, Hydrometeor Classification, and Melting Layer

26. Precipitation Estimation Improvement with Dual-Pol Based on 43 events (179 hrs) of radar rainfall data comparisons to a dense network of rain gauges in C. OK

27. Dual-Pol QPE Output • 9 new products • Match Legacy PPS • Instantaneous Rate • User Selectable (Up to 10 durations) for the NWS • Difference products

28. Hydrometeor Classification Algorithm Lgt/mod rain Heavy rain Hail “Big drops” Graupel Ice crystals Dry snow Wet snow Unknown AP or Clutter Biological Current Classification Options • Algorithm makes best guess of dominant radar echo type • For every radar elevation angle

29. 20000 ft MSL SOO-DOH Images\kcri_0.5_HC_20080408_0638.png

30. Hydrometeor Classification Algorithm Challenges • Verification • “Fuzzy” Logic and ambiguity between types • Typical Radar sampling limitations (snow at 2000 ft AGL may not be snow at the surface)

31. Melting Layer Detection Algorithm • Mixed phase hydrometeors: Easy detection for dual-pol! • Z typically increases (bright band) • ZDRand KDP definitely increase • Coexistence of ice and water will reduce the correlation coefficient (CC ~0.95-0.80) • Algorithm overlay product for top and bottom of melting layer

32. ML Product in AWIPS

33. Part 2: What Dual-Pol Can/Can’t Do

34. Highlights of How Dual-pol Data Will Aid Decision Makers P P P P Better precipitation estimation Improved detection and mitigation of non-weather echoes Melting layer identification Hydrometeor classification New/improved storm signatures (NEXT)

35. Hail Detection HAIL HAIL Horizontal Reflectivity Differential Reflectivity

36. Thunderstorm Updraft Example“ZDR Columns” Melting layer Updrafts Horizontal Reflectivity 2.4° tilt Differential Reflectivity

37. Thunderstorm Updraft ExampleKDP Melting layer Updrafts Horizontal Reflectivity 2.4° tilt Specific Differential Phase Shift

38. Thunderstorm updraft exampleCC Melting layer Updrafts Horizontal Reflectivity 2.4° tilt Correlation Coefficient

39. ZDR Column Issues • Dry environments • Cloud base near 0oC • Shallow warm cloud depths • Depth above in cloud 0oC could be proxy for relative updraft strength • If exists, then good chance of lead time on hail production and thus storm severity

40. Tornadic Debris Signature Storm-Relative Velocity Reflectivity Lowest Cut 0.5 deg CC

41. Reflectivity 0.5 deg CC

42. What Dual-PolCan do • Vastly improve precip estimation • Detect hail aloft, infer presence of giant hail • Detect melting layer and improve winter weather nowcasting • Improve identification of non-weather echoes • Offer best guess at P-type aloft • Improve confidence in damaging tornado close to the radar

43. What Dual-polCan’tdo • Overcome the laws of physics • Perfect rainfall estimation at each gate • Exact hail sizes • Identify surface precipitation type • Detect every tornado • Predict any tornado

44. Part 3: Deployment and Training Plans

45. When/What is the Impact? • All WSR-88Ds upgraded 2010-2012 • 10-14 days radar downtime during upgrade

46. Target Two Critical Stakeholders

47. KICT upgraded Mid-July 2010* Training/Deployment High-level Schedule

48. Questions? Tel: 405-325-1091 Email: Paul.T.Schlatter@noaa.gov