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Polarization diversity at McGill Radar Observatory

Polarization diversity at McGill Radar Observatory. Dual Polarization on the S-band Radar. AND A SIMULTANEOUS, BUT SEPARATE, RECEPTION OF THE VERTICAL AND HORIZONTAL COMPONENTS OF THE ELECTRIC VECTOR. WE IMPLEMENTED A TRANSMISSION AT 45 DEGREES: EQUAL POWER IN . E V and E H.

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Polarization diversity at McGill Radar Observatory

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  1. Polarization diversity at McGill Radar Observatory • Dual Polarization on • the S-band Radar.

  2. AND A SIMULTANEOUS, BUT SEPARATE, RECEPTION OF THE VERTICAL AND HORIZONTAL COMPONENTS OF THE ELECTRIC VECTOR. WE IMPLEMENTED A TRANSMISSION AT 45 DEGREES: EQUAL POWER IN. EV and EH Polarization Diversity: the concept Because of the drops’ deformation the medium isanisotropic for EM propagation and scattering. Thus, the vertical and the horizontal components of the electric vector, EV and EH, are scattered differently and propagate at different speeds.

  3. Phase difference between EH and EV . • Measures the total path-integrated “mass x deformation”. • (the radial derivative of , KDP, is often displayed) • Ratio of to . • Measures the average deformation (axis ratio) of targets. • Correlation between and . • Measures the variability of shapes and orientations of the targets. What information do we obtain from polarization diversity at 450 transmission and simultaneous reception of ZH and ZV? M E A S U R A B L E S • Equivalent reflectivity.

  4. Polarimetric measurements at 2.7 PPI Bright band not evident in Ze is well seen in ZDR and ρHV Convective shower of similar Ze as the BB appears different in ZDR and ρHV

  5. Polarimetric Measurements of BIRDS • Vr shows lower birds • moving NE-SW while higher • birds travel NW-SE. • 2) ZDR is generally high and • partly dependent on azimuth • 3) φDP strongly dependent on • azimuth (depending on • whether the bird is viewed • lengthwise or head-tail. • 4)ρHV: Unexplained

  6. ZDR and KDP are monotonic functions of R Connection between R and polarimetric measurables

  7. Errors due to DSD variability: reliable 5-yr DSDs True R Estimated R

  8. Several sources of errors in rain estimation:Polarimetric radar Drop deformation ? Measurement noise in KDP, ZDR Methods of deriving R-(Zh,v,KDP,ZDR) relationships DSD variability: Zh,v, KDP, ZDR R

  9. Propagation of the DSD variability and measurement noise into R DSD variability from 5-year data Assumed radar noise: σZh = 0.3 dB σZDR = 0.17 dB σKDP = 0.11deg/km

  10. But zero Doppler velocity is also found in precipitation. GROUND CLUTTER (identified By zero Doppler velocity) AFTER More likely birds taking advantage of the good winds. Partial beam blocking by a nearby building GROUND CLUTTER IDENTIFICATION OF ARTIFACTS, etc. (0.9º PPI through FLOYD) BEFORE DUAL POLARIZATION Is it all rain?

  11. 2.70 PPI in stratiform precipitation Z Zdr Target ID

  12. Vr Z Z Vr

  13. Z (a = 0.5 deg) ZDR (a = 0.5 deg) Rain/hail Target ID (a = 0.5 deg) Hail KDP (a = 0.5 deg Zoom on the strong cell (0.5° PPI) Light rain Mod. rain

  14. Z ZDR Target ID KDP Dry snow graupel Rain/Hail Wet snow Vertical section through the strong cell

  15. r =120km (h =2.6km) mesocyclone 80 (1.7) KDP (deg/km) Hi Z, low ZDR, low KDP: HAIL ! HAILSTORM IN THE OTTAWA REGION (24/5/00) R Z (mm/h) (dB) Vr 120 ZDR (dB) 120 80

  16. Target ID r =120km (h =2.6km)

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