1. Radar Palet e Home Dual Polarized Analysis & Diagnosis 1 Dual Polarized Radar What is polarimetric radar Polarimetric products Uses of these ‘raw’ outputs in forecasting Winter precipitation field study Particle ID algorithms Etc – other topics Dual Polarized Analysis and Diagnosis (Important Material – linked to page 80)Dual Polarized Analysis and Diagnosis

2. Radar Palet e Home Dual Polarized Analysis & Diagnosis 2 Dual Polarization Radar Courtesy: http://cimms.ou.edu/~schuur/radar.html - Particles have different shapes and orientations -Horizontally and vertically polarized signals encounter different amounts of water mass and return different signals - From these differences, you can infer some properties of the hydrometeors

3. Radar Palet e Home Dual Polarized Analysis & Diagnosis 3 Polarization Products Radar Reflectivity Z h Differential Reflectivity Z DR Correlation coefficient ρ HV Differential Phase φ DP Specific differential phase K DP

4. Radar Palet e Home Dual Polarized Analysis & Diagnosis 4 Radar Reflectivity Zh Conventional radar product Depends on size (D 6 ) and number density Sensitive to calibration and partial beam blocking Prone to attenuation for shorter microwaves C- band (5 cm)

5. Radar Palet e Home Dual Polarized Analysis & Diagnosis 5 Differential Reflectivity (ZDR) Ratio of scattered H and V power returns (PHH/PVV) Function of the particle shape and orientation Independent of absolute calibration and particle concentration Affected by differential attenuation

6. Radar Palet e Home Dual Polarized Analysis & Diagnosis 6 Differential Reflectivity (ZDR) Drop shape as a function of size:

7. Radar Palet e Home Dual Polarized Analysis & Diagnosis 7 Differential Reflectivity (Z DR ) H/V Good discriminator between heavy rain and hail. For hail Z DR ~1 (hail is round and tumbling) For heavy rain Z DR is large since Z HH >>Z VV (big drops are Big Macs – large horizontally & smaller in the vertical) Low values for ground clutter (< 0) (buildings tend to be vertical…) High values for biological scatters (> 3) (birds and bugs have winds – horizontally larger than vertical dimension…) Intermediate values meteorological ZDR > 0  H dim greater ZDR < 0  V dim greater ZDR ~ 0  spherical or randomly oriented

8. Radar Palet e Home Dual Polarized Analysis & Diagnosis 8 Differential Reflectivity (Z DR ) Light rain (0.5 -1.0 dB) Moderate rain (1.5 - 2.0 dB) Heavy rain (2.5 - 3.0 dB) Rain/Hail (0.0 - 1.0 dB) Dry snow (0.0 - 0.3 dB) Wet snow (1.0 - 2.0 dB) Ice crystals (2.0 - 3.0 dB)

9. Radar Palet e Home Dual Polarized Analysis & Diagnosis 9 Correlation Coefficient – ρ HV Correlation of the time series of H and V returns Not quantitative measurement Independent of calibration, attenuation and particle concentration A measure of the variety of particle shapes and fall modes

10. Radar Palet e Home Dual Polarized Analysis & Diagnosis 10 Correlation Coefficient – ρ HV For radar bins with single particle shape Zh/Zv is constant in series of pulses. No variance equals 1 on “rhoHV” display Mixed particles.. Zh/Zv not constant and variance recorded as less than 1.

11. Radar Palet e Home Dual Polarized Analysis & Diagnosis 11 Correlation Coefficient – ρ HV ~ 1 for single type of hydrometeors in a preferred orientation (rain or snow) Decreases with increasing diversity of hydrometeor shapes and orientation More significant if particles wet or large and irregular

12. Radar Palet e Home Dual Polarized Analysis & Diagnosis 12 First Application of Dual Polarized Radar in Canada Doppler Radar

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14. Radar Palet e Home Dual Polarized Analysis & Diagnosis 14 Rain with moderate northeast winds It is OK to look out the window!

15. Radar Palet e Home Dual Polarized Analysis & Diagnosis 15 Polarized Radar

16. Radar Palet e Home Dual Polarized Analysis & Diagnosis 16 Sphereical Flat Sphere ical ZDR

17. Radar Palet e Home Dual Polarized Analysis & Diagnosis 17 New Polarized Radar Old Doppler Radar These are not Stereo Radars

18. Radar Palet e Home Dual Polarized Analysis & Diagnosis 18 Sphereical More Blockage

19. Radar Palet e Home Dual Polarized Analysis & Diagnosis 19 SNOW Spherical RAIN Flat Some ice pellets… snow and even rain at the office Differential Phase is caused by compression of the microwaves in the hyrdometeor medium and the different horizontal and vertical presented by non spherical hydrometeors.

20. Radar Palet e Home Dual Polarized Analysis & Diagnosis 20 SNOW Spherical RAIN Flat

21. Radar Palet e Home Dual Polarized Analysis & Diagnosis 21 Rain-Snow Boundary Case Ground clutter Radome interference snow rain Wet snow and rain

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23. Radar Palet e Home Dual Polarized Analysis & Diagnosis 23 Bright band Case Differential Reflectivity Differential Phase Reflectivity Correlation Coefficient Bright Band

24. Radar Palet e Home Dual Polarized Analysis & Diagnosis 24 Icing Aloft Differential Reflectivity Differential Phase Reflectivity Correlation Coefficient LGT-MDT MXD ICG @ 14KFT

25. Radar Palet e Home Dual Polarized Analysis & Diagnosis 25 Another Day December 23, 2004

26. Radar Palet e Home Dual Polarized Analysis & Diagnosis 26 ρ HV Uniform Snow Change to Freezing Rain Rain

27. Radar Palet e Home Dual Polarized Analysis & Diagnosis 27 Particle Characteristics In Cross-Section ρ HV Uniform Snow Less Uniform Melting Snow-Liquid Mix More Uniform Liquid High Correlation  Uniform Particles Lower Correlation  Mixed Particles High Correlation  Uniform Particles Infer FRLVL Melting Melted Snow Snow-ZR- ZR-

28. Radar Palet e Home Dual Polarized Analysis & Diagnosis 28 Precipitation Transition Case January 21, 2006

29. Radar Palet e Home Dual Polarized Analysis & Diagnosis 29 Rain-snow transition at CARE VertiX radar: at ~0800Z, fall velocities show change from rain after 1030Z, light falling snow only rain mix /melting / aggregation snow

30. Radar Palet e Home Dual Polarized Analysis & Diagnosis 30 0700-0710Z: Rain Rain-snow transition at CARE 0730-0740Z: Rain/Snow HVSD 10-minute analysis

31. Radar Palet e Home Dual Polarized Analysis & Diagnosis 31 Rain-snow transition at CARE 1307-1317Z: Dry snow HVSD 10-minute analysis 0800-0810Z: Wet Snow/ Dry Snow

32. Radar Palet e Home Dual Polarized Analysis & Diagnosis 32 ZZ DR ρ HV Round/tumbling H and V are similar Sig Reflectivity Correlated in Time Dry Snow

33. Radar Palet e Home Dual Polarized Analysis & Diagnosis 33 Heavy Wet Snow

34. Radar Palet e Home Dual Polarized Analysis & Diagnosis 34 Uncorrelated RhoHV in a sea of correlations Suggests a phase change line.

35. Radar Palet e Home Dual Polarized Analysis & Diagnosis 35 Significant Reflectivity but not the same Along the entire length of the band

36. Radar Palet e Home Dual Polarized Analysis & Diagnosis 36 Differential Reflectivity ZDR show a change Along the entire length of the band ZDR > 0  H dim greater ZDR < 0  V dim greater ZDR ~ 0  spherical or randomly oriented SNOW RAIN Wet SNOW Wet SNOW – shaped like flatten badminton shuttlecocks

37. Radar Palet e Home Dual Polarized Analysis & Diagnosis 37 1120Z Z DR Vr 2006-01-21: Radome attenuation Z DR anomaly in northern sector of radar picture; > 3dB high Rain-snow transition zone approaches and passes radar origin Note low level wind direction affects attenuated sector 1030Z Z DR 50 minutes

38. Radar Palet e Home Dual Polarized Analysis & Diagnosis 38 Snow Squall Case February 24, 2006

39. Radar Palet e Home Dual Polarized Analysis & Diagnosis 39 ZZ DR ρ HV

40. Radar Palet e Home Dual Polarized Analysis & Diagnosis 40 Polarimetric Radar and Snowsqualls Snowfall rates of 5-10 cm an hour are not uncommon in squalls although water equivalents may be only 20 or 30 to 1. Do these “big squalls” look any different with polarimetric radar? Feb 6 2006 a very strong snowsquall went though the Toronto area. 30 cm accumulation east of city.

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42. Radar Palet e Home Dual Polarized Analysis & Diagnosis 42 Differential Reflectivity ZDR is negative so the snow flake tend to be vertically larger ZDR > 0  H dim greater ZDR < 0  V dim greater ZDR ~ 0  spherical or randomly oriented

43. Radar Palet e Home Dual Polarized Analysis & Diagnosis 43 RhoHV is nearly perfectly correlated The flakes are all the same

44. Radar Palet e Home Dual Polarized Analysis & Diagnosis 44 Doppler shows a northwesterly flow at an angle to the long axis of the snowsquall. Is the snowsquall going to remain stationary? Is the snowsquall going to drift southward?

45. Radar Palet e Home Dual Polarized Analysis & Diagnosis 45 Fuzzy Logic to Radar Interpretation Inputs (radar variables) Decision process (membership functions) Output classification (hydrometeor type)

46. Radar Palet e Home Dual Polarized Analysis & Diagnosis 46 Types of Membership Functions Typical one-dimensional Trapezoid Membership Function

47. Radar Palet e Home Dual Polarized Analysis & Diagnosis 47 2D Trapezoid Membership Function 2-D TMF for Moderate Rain

48. Radar Palet e Home Dual Polarized Analysis & Diagnosis 48 “Simple” Membership Functions

49. Radar Palet e Home Dual Polarized Analysis & Diagnosis 49 King HCA (iParCA) IDL code emulating the NSSL algorithm Three schemes of particle classification: –Simple –Summer –Winter

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52. Radar Palet e Home Dual Polarized Analysis & Diagnosis 52 Radar and snow accumulation The Z-S relationship often produces poor results. Can polarimetric parameters improve this situation

53. Radar Palet e Home Dual Polarized Analysis & Diagnosis 53 6 hour snowfall accumulation map December 08, 2006 YXU London airport Exeter radar estimated 2-3 cm YXU observed 12 cm with water equivalent of 11 mm

54. Radar Palet e Home Dual Polarized Analysis & Diagnosis 54 Radar and snow accumulation The Z-S relationship often produces poor results. Can polarimetric parameters improve this situation Yes… but the work isn’t completed yet…

55. Radar Palet e Home Dual Polarized Analysis & Diagnosis 55 Dual Polarized Radar Doppler was started in Canada in research mode at King City in 1985 It took 10 years to understand the power of the outputs It took 15 years to dopplerize the Canadian radar network Dual Polarized radar was started at King City in 2004…

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80. Radar Palet e Home Dual Polarized Analysis & Diagnosis 80 Dual Polarized Radar Analysis and Diagnosis Strategies An operational guide to getting the most information from Dual Polarized radar: Under construction

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