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

Reflectivity Long PRT EL = 0.5 deg 10/08/02 15:11 GMT Phase Coding

Doppler Velocity Phase coding, medium PRT EL = 0.5 deg 10/08/02 15:11 GMT Doppler Velocity Processing as on WSR-88D v a = 23.7 m s -1, r a = 175 km Phase Coding

Staggered PRT Reflectivity Staggered PRT EL = 2.5 deg 04/06/03 4:42 GMT

Staggered PRT v a = 25.4 m s -1 v a = 45.2 m s km 184 km KTLX Doppler Velocity VCP 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 : 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 km 2 ) –capable of predicting tornadoes, strong winds, hail, and other hazards

END These are the news from the Prairie Town of Norman Were all meteorologists are No 1 And Engineers are second to none