Surveillance Weather Radar 2000 AD
Dec 23, 2015
Surveillance Weather Radar 2000 AD
Weather Radar Technology- Merits in Chronological Order
WSR-57
WSR-88D
WSR-07PD
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
Capability of the NSSL’s R&D 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
Oversampling
• To increase speed of volume coverage
• To decrease errors in estimates of reflectivity, velocity, spectrum width, and polarimetric variables
Z, Standard Processing, Aug 04
Z, from Decorrelated Samples
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
ReflectivityLong PRT
EL = 0.5 deg
10/08/02 15:11 GMT
Phase Coding
Doppler VelocityPhase coding, medium
PRT
EL = 0.5 deg
10/08/02 15:11 GMTDoppler Velocity
Processing as on WSR-88D
va = 23.7 m s-1, ra = 175 km va = 23.7 m s-1, ra = 175 km
Phase Coding
Staggered PRT
ReflectivityStaggered PRT
EL = 2.5 deg
04/06/03 4:42 GMT
Staggered PRT
va = 25.4 m s-1 va = 45.2 m s-1
148 km
184 km
KTLX Doppler VelocityVCP 11 – Batch Mode
KOUN Doppler Velocity
Staggered PRT (184 km/276 km)EL = 2.5 deg
04/06/03 4:42 GMT
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)
Fields of polarimetric variables
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
Stratiform Rain vs Snow
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
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
Major Endeavor
• Explaining bulk hydrometeor properties that cause distinct polarimetric signatures in convective storms
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
END
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