Surveillance Weather Radar 2000 AD

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Surveillance Weather Radar 2000 AD
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Weather Radar Technology- Merits in
Chronological Order
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Technology Developments

• Digital receivers
• Easy to achieve sampling rate higher than
  reciprocal of pulse (oversampling)
• Versatile circuits for transmitter control
• Easy to phase code, to interleave PRTs (staggered
  and other), to compress pulse
• Signal processing on general purpose computers
  (PCs)
• Easy to program algorithms and analyze Doppler
  spectra

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Capability of the NSSLs RD weather surveillance
radar

• Doppler and Dual Polarization
• Phase coding of transmitted pulses
• Transmission of arbitrary non uniform pulse
  sequence including staggered PRT
• Oversampling
• by a factor of 5 in Dual Polarization Mode
• By a factor of 10 in Single Polarization Mode
• Arbitrary scanning strategy (including RHI)
• Recording of time series data

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Oversampling

• To increase speed of volume coverage
• To decrease errors in estimates of reflectivity,
  velocity, spectrum width, and polarimetric
  variables

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Z, Standard Processing, Aug 04
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Z, from Decorrelated Samples
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Mitigation of range velocity ambiguities

• Phase coding at lower elevations
• Staggered PRT at higher elevations
• Demonstration of clutter filtering for both
  schemes
• Integration into volume coverage patterns
• Inclusion of oversampling
• Adaptive automatic choice of PRTs based on
  obscurations in immediately preceding scans

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Phase Coding
10/08/02 1511 GMT
EL 0.5 deg
ReflectivityLong PRT
10
Phase Coding
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Staggered PRT
04/06/03 442 GMT
EL 2.5 deg
ReflectivityStaggered PRT
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Staggered PRT
04/06/03 442 GMT
KTLX Doppler VelocityVCP 11 Batch Mode
KOUN Doppler Velocity Staggered PRT (184 km/276
km)
EL 2.5 deg
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Dual Polarization at NSSL

• 1983 Upgrade of Cimarron radar to dual
  polarization switching between horizontal and
  vertical polarization
• 1984 Collection of first (anywhere) dual
  polarization time series data
• 1985 to 1989 Definition of the complete set of
  polarimetric variables. Development of schemes to
  obtain these variables together with spectral
  moments
• 1992 First (anywhere) collection of polarimetric
  variables at all range locations
• 1992 to present Development of schemes to
  classify hydrometeor type. Improvement of
  rainfall estimation. Design of a system
  functionally compatible with the WSR-88D
  simultaneous transmission and reception of
  horizontally and vertically polarized waves
• 2002 Upgrade of KOUN radar to dual polarization
• 2002-2003 Joint POLarization Experiment (JPOLE)

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Fields of polarimetric variables
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Dual Polarization - Benefits

• Vastly superior data quality calibration,
  mitigation of attenuation and beam blockage
  effects
• Discrimination between insects, birds, ground
  echoes, and precipitation
• Superior measurement of rainfall
• Detection of hail
• Classification of precipitation rain vs
  freezing rain vs snow
• Determination of hail size
• Measurement of snowfall
• Icing detection

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Stratiform Rain vs Snow
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Imminent Goals

• Combining techniques to mitigate range and
  velocity ambiguities with optimum (pseudo
  whitening) procedure to increase speed of volume
  coverage and decrease errors of estimates
• Incorporating the above combined technique into
  dual polarization radar
• Developing adaptive scanning strategy for agile
  beam phased array radar

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Three Challenges

• Direct estimation of wind transverse to the radar
  beam
• Determination of the alias interval of Doppler
  velocity from a single pulse
• Estimation of the forward propagation coefficient
  using returns from hydrometeors or biological
  scatterers

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Major Endeavor

• Explaining bulk hydrometeor properties that cause
  distinct polarimetric signatures in convective
  storms

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Major Endeavor

• Assimilation of radar data into local NWP (short
  term 3 h, fine resolution 1 km) model
• coupled to distributed hydrological model for use
  over small watersheds ( 1000s km2)
• capable of predicting tornadoes, strong winds,
  hail, and other hazards

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END

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