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CAPS Radar QC and Remapping

CAPS Radar QC and Remapping. Keith Brewster Radar Assimilation Workshop National Weather Center 18-Oct-2011. Radar I/O & Remapping Capabilities. Remapping Drivers 88D2ARPS NEXRAD WSR-88D Level-II China 98D WSR-98D Level-II TDWR Output to Solo DORADE NIDS2ARPS NEXRAD Level-III

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CAPS Radar QC and Remapping

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  1. CAPS Radar QC and Remapping Keith Brewster Radar Assimilation WorkshopNational Weather Center 18-Oct-2011

  2. Radar I/O & Remapping Capabilities Remapping Drivers • 88D2ARPS • NEXRAD WSR-88D Level-II • China 98D WSR-98D Level-II • TDWR • Output to Solo DORADE • NIDS2ARPS • NEXRAD Level-III • NCRAD2ARPS • CASA NetCDF • WDSS-II Tilt NetCDF (KOUN, Taiwan data) • OU-PRIME NetCDF • FORAY NetCDF (field project data)

  3. y x Radar Sampling Problem-Horizontal b a

  4. Radar Sampling Problem -Vertical z b x a

  5. CAPS Radar Remapping Local least-squares interpolation/smoothing Quadratic in horizontal Linear in vertical • Smoothsdense data • Superobbing consistent with model grid • Interpolates accurately in data-sparse regions • Can be applied in 2D on ray surface. • Ray paths: 4/3-earth ray path or estimate of bulk refractive index gradient with height • Full range of map projections & vertical grid stretching supported

  6. Remapping to Dx = 2 km

  7. Remapped Radar Field x-z Cross-section

  8. AP/Clutter Detection • Despeckle (remove isolated point targets) • Calculate 3 terms in small regions around each gate • DdBZ between 0.5° and 1st tilt above 1.1°DdBZ < -12 dBZ assoc with AP • DdBZ < -20 dBZ assoc with ground targets such as wind turbines • Texture.. Spin Change. A lot of changes in sign of gate-to-gate reflectivity gradients associated with AP. • Mean Radial VelocitySmall magnitude of mean radial velocity associated with AP • Weak check: Fails 2 or more of 3 checks • Strong check: Fails 1 or more checks

  9. Sunrise/Sunset Radials

  10. Sunrise/Sunset Radials • Point source interference, such as sun, produces characteristic signature. • High percentage of radial is non-missing. • Reflectivity factor increasing linearly with range. • Small variance from linearity.

  11. KDDC Sunset & Clutter Raw Obs AnomalousRadial Removed Clutter Removal

  12. Sea Clutter

  13. CAPS Real-time Velocity QC & Dealiasing • Three Pronged Approach • Background Comparison • Most useful for removing shear with height due to mean wind profile • Background from model or VAD • Two-dimensional continuity • Applied in multiple directions • Final Quadratic fit for uncertain points.

  14. Gate-to-Gate Shear Check Begin Mean Wind Profile Find Radial Perpendicular to Mean WInd Shear Comparison Template Forward Pass Repeat Reverse Pass Continue to Remapping Step Direction

  15. Multiple Folded Data Mean Wind Raw Obs Shear Check

  16. KTLX 10 May 2010 6.5° Scan Raw Obs Mean Wind Shear Check Quad Fit

  17. Ongoing Work Increasing Flexibility • New NAMELIST control file added • Correction factors for mobile radars • Moving tunable parameters to NAMELIST Dual-Pol for WSR-88D • Some experience with CASA • Additional algorithms for clutter and non-precip echo identification & removal Radial-by-radial ray tracing. Can we use vortex recognition/fitting techniques to improve QC and analysis near strong vortices?

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