1 / 77

Radar Artifacts

Radar Artifacts. Radar Beam Filling Non Uniformity Of Vertical Distribution Of Precipitation Variations In Z-R Relationship Attenuation By Intervening Precipitation Beam Blocking Attenuation Due To A Wet Radome Electromagnetic Interference Ground and Other Clutter Anomalous Propagation

aerona
Download Presentation

Radar Artifacts

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Radar Artifacts • Radar Beam Filling • Non Uniformity Of Vertical Distribution Of Precipitation • Variations In Z-R Relationship • Attenuation By Intervening Precipitation • Beam Blocking • Attenuation Due To A Wet Radome • Electromagnetic Interference • Ground and Other Clutter • Anomalous Propagation • Antenna Accuracy • Electronics Stability • Processing Accuracy • Radar Range Equation

  2. The Schematic Radar

  3. Radar Sources of Error

  4. Radar System Limitations

  5. Non-meteorological effects

  6. Meteorological Effects

  7. Radar sensitivity and blockage • Not all radars are equal • Most are retrofitted Enterprise radars with 1.1° beam width and 4 m dishes • Some are Andrews radars with 0.65° beam width and 6 m dishes • Spirit River AB, WWW, has only 1.6° beam width! • Many have obvious issues • differences in sensitivity between each other • blockages • But many have less obvious, but significant problems that only become apparent with long-term precipitation accumulations

  8. BC 15 Day Precip Accum CAPPI 1.5 km WWW 1015m XPG 1118m XSS 1829m WUJ 60m XSI 700m

  9. Prairies 30 Day Precip Accum PRECIPET

  10. Nrn Ontario 2 Day Precip Accum CAPPI 1.0 km Feb 16-17 2008

  11. 2 Day Precip Accum CAPPI 1.0 km Mar 8-9 2008 Srn Ontario

  12. Srn Quebec 2 Day Precip Accum CAPPI 1.0 km Mar 8-9 2008 N

  13. Atlantic 2 Day Precip Accum CAPPI 1.0 km Jan 28-30 2008

  14. Sources of Error - Radar Dome Wetting

  15. Sources of Error • Intervening precipitation • Wet radome • Beam blocking

  16. Attenuation: What lies beyond?

  17. Example of Attenuation in Precipitation Wedge of attenuation Foreground Storm

  18. Cross Section constructed along this line

  19. 60 dbZ core

  20. Sources of Error - Cell Blocking Cell blocking

  21. ??? ??? Spirit River, AB/BC BEAM BLOCKING Persistent Ground clutter Beam blockage N Clear Hills S Rockies

  22. Wedge of attenuation Foreground Storm Attenuation

  23. Attenuation • Warm Frontal Supercell

  24. Attenuation • north • end • of • derecho?

  25. RadomeWetting You just Checked The radar… NO PROBLEM… PROBLEM !

  26. Sources of Error - Sidelobes Orographic Enhancement 3D View of Real Beam

  27. Sources of Error - Blocking Impacts on Precipitation Estimates Why no precipitation amount maximum on the peaks? No PCPN? No PCPN?

  28. Bright Band • Melting snowflakes are large bright radar targets • Reflectivity from melting snow is larger than that of the rain below or the snow above as falling snow passes through the melting layer • Huge impact on quantitative precipitation estimates

  29. Bright band shows up as ring (or partial ring) of high Z centred on the radar Bright band

  30. Melting of Snow Flakes starts at 2.5 km height Bright Band • Freezing Level ~2.5km AGL • Either associated with Rain or Freezing Rain

  31. Melting Starts Melting Bright BandTime/height Display Time

  32. But not on the lower elevation scan, in this case

  33. Melting layer shows as peak in Z (note it shows up best in data for the 3.5 degree scan. Why?)

  34. Sources of Error - Conventional Ground Clutter

  35. Multi-path Echoes

  36. Spot the AP

  37. Corresponding Radial Velocity Image

  38. Doppler Reflectivity AP versus Real - Compared

  39. Sources of Error - Anomalous Propagation AP Strong inversions Typical early morning after clear (long) nights – fall maximum Over cold water surface – spring maximum

  40. Anomalous Propagation of the Radar Beam Only Real Weather AP and Real Weather The Doppler Velocity View

  41. AP and Frontal Analysis Anomalous Precipitation AP

  42. AP … Water Vapour and Fog VISIBILITY Probably still OK

  43. Ground Clutter • Direct reflections from ground targets, either in the main lobe or sidelobes • Echoes are unusually variable in space, but constant in time (in contrast to AP, which is variable in time) • Well handled by clutter filters during signal processing

  44. Ground Clutter • Rockie Mountains • persistent • even on EchoTop product

  45. Ground Clutter Bethune, Saskatchewan • Missouri Couteau • only seen on 0.5PPI

  46. Radar Beam Overshooting

  47. 0.3 Degree PPI 0.3 Degree PPI PPI and CAPPI 4.0 km CAPPI 1.5km CAPPI

  48. NORTH Illustration Using King Radar Georgian Bay Lake Simcoe Lake Huron Lake Ontario

  49. Calculated horizon in Panorama Far side of LkOntario To G.Bay To Lk Huron Lake itself Lk Simcoe North East South West North Shaded by distance to horizon. Red is basically the neighbourhood (“look down”) and mauve is see forever.

  50. The Digital Elevation Map isn’t 100% complete or up-to-date. Largest Landfill in Canada Buildings Trees YOU are HERE Behind the trees

More Related