Real-Time Dissemination of Hurricane Wind Fields Determined from Airborne Doppler Radar

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Real-Time Dissemination of Hurricane Wind Fields
Determined from Airborne Doppler Radar

• John Gamache
• NOAA/AOML/Hurricane Research Division
• Collaborators Joseph Griffin, Peter Dodge,
• Nancy Griffin
• Supported by NOAA Joint Hurricane Test Bed

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Project Goals

• Develop a hurricane wind-field analysis in real
  time and make it available to hurricane
  specialists at the Tropical Prediction Center
• Send reliable observations to the Environmental
  Modeling Center at NCEP for assimilation testing
  in numerical simulations

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Airborne Radar on NOAA P-3

• Airborne Radar
• Scanning axis along aircraft fuselage
• 3-cm wavelength
• Measures reflectivity (precipitation content)
• Measures radial velocity from aircraft

FOR MORE INFO...
http//www.aoml.noaa.gov/hrd/project2003/doppler.h
tml
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Jorgensen et al., 1983, J. Climate Appl. Meteor,
22, 744-757
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Present Analysis Software

• Reliable--Works on multiple platforms
• Mass-conserving
• Consistent to within 1-2 m/s with Doppler
  observations
• Operates in research mode
• Researcher has plenty of time to make decisions
  regarding errors/assumptions
• Final analysis may take years

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range from center (km)
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Main sources of error from NOAA P-3 Airborne
Doppler Radar

• Doppler radial velocity ambiguity
• Reflection from sea surface
• Incorrectly measured antenna pointing direction
• Noise

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Doppler Radial Velocity Ambiguity

• Velocities determined from radar pulse phase
  measurements
• -180o to 180o phase range
• Corresponds to a radial velocity range
• P3--range from -12.9 to 12.9 up to -25.8 to 25.8
  meters per second--Nyquist velocity
• Angles lt -180o or gt 180o are ambiguous
• Corresponding velocity aliased or folded
• True velocity is measured aliased velocity plus 2
  times a multiple of Nyquist velocity

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Noise

• Receiver Noise--power threshold
• Meteorological Noise
• Turbulence in boundary layer
• Turbulence in outflow from convection

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Reflection from sea surface

• Main antenna lobe
• Beam width vs precipitation content
• Side lobe
• Annular--radius is height of aircraft
• Fairly weak
• Second trip--confusion with previous pulse
• High spectral width
• Usually removed easily by noise edit

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Antenna pointing direction errors

• Pointing direction relative to aircraft
• Aircraft attitude
• HRD has software to estimate these errors

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Accomplishments

• Sea-surface reflection removal software
  developed/preliminary test
• Speckle removal developed
• Minor bugs in present de-aliasing removed
• Two-dimensional de-aliasing scheme development
  begun
• Preliminary discussions with EMC on structure of
  superobs

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Doppler Radial Velocity
Hurricane Humberto 231754 UTC 23 Sep 2001
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Doppler Radial Velocity
Hurricane Humberto 232842 UTC 23 Sep 2001
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Doppler Radial Velocity
Hurricane Humberto 232855 UTC 23 Sep 2001
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Doppler Radial Velocity
Hurricane Humberto 232901 UTC 23 Sep 2001
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Comparison of Analyses Created from
Research-Quality and Automatically Edited
Data At 1 km level in Hurricane Humberto 2330
UTC on 23 September 2001
Research Quality
Automatic
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Next Tasks

• Improve two-dimensional de-aliasing
• Produce consistent velocities within contiguous
  regions of data
• Ensure overall velocity in each contiguous region
  is consistent with expected hurricane flow

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Next Tasks

• Begin interaction with NCEP/EMC
• Determine structure of superobs
• Begin determination of data error covariance of
  Airborne Doppler radial velocity measurements
• Install new software on airborne workstations for
  2004 Hurricane Season

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Future Tasks

• Produce test wind analysis aboard aircraft during
  2004 Hurricane Season
• Test sending a prototype superob by end of 2004
  Hurricane Season
• Develop analysis display for Hurricane
  Specialists during off season
• Begin determination with EMC of Doppler data
  error covariance
• Send wind analysis to specialists during 2005
  Hurricane Season
• Continue testing superob transmission during 2005
  Hurricane Season