GBVTD: A SingleDoppler Radar Wind Retrieval Technique

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GBVTD A Single-Doppler Radar Wind Retrieval
Technique

• Shanna Pitter
• AT741 Spring 2004

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Ground Based Velocity Track Display (GBVTD)

• Developed by Lee et. al. 1994 for aircraft radar
  then for WSR-88D (1999)
• Retrieves tangential and radial velocity using
  single Doppler radar data
• GBVTD analyzes storm-centered rings of data to
  determine the hurricane primary circulation using
  Fourier analysis

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Ground-Based Velocity Track Display (GBVTD)
Constant Rotation
Constant Inflow
Combined flow
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How do you do it?

• Using WSR-88D Archive Level II data
• Make Constant Altitude Plan Position Indicator
  (CAPPI) plots
• Find the centers using a GBVTD Simplex center
  finding algorithm
• Apply the GBVTD algorithm to determine the
  coefficients at each radius and altitude

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Limitations

• GBVTD wind is an approximation of the full
  circulation where asymmetric radial wind is
  aliased into tangential wind
• Cross beam mean flow affects tangential wind
  result
• Sensitive to the center fixes

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Example of the GBVTD technique
GBVTD equivalent
Nexrad
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Hurricane Bret

• Occurred 18- 25 August, 1999
• Achieved a 125 knot, category 4 rating on the
  Saffir-Simpson scale at its peak
• Made landfall between the radar sites of
  Brownsville (KBRO) and Corpus Christi (KCRP), TX
• Amazing dataset gathered from both the ground and
  air

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Tangential Wind
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Radial Wind
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R-Z mean Tangential Wind
KCRP
KBRO