Signal Design and Processing Techniques for WSR-88D Ambiguity Resolution (original) (raw)
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Range and velocity ambiguity mitigation techniques for the WSR-88D weather radar
IEEE International IEEE International IEEE International Geoscience and Remote Sensing Symposium, 2004. IGARSS '04. Proceedings. 2004
Several mechanisms are currently provided to alleviate effects of range overlaid echoes and velocity aliasing in the Weather Surveillance Radar-1988 Doppler (WSR-88D). However, due to limitations in these techniques, observation of severe weather phenomena is significantly impaired. This paper presents results from a multi-year study at the National Severe Storms Laboratory dealing with methods to mitigate the effects of range and velocity ambiguities in the WSR-88D.
Design, Implementation, and Demonstration of a Staggered PRT Algorithm for the WSR-88D
Journal of Atmospheric and Oceanic Technology, 2004
This paper describes the implementation of the staggered pulse repetition time (PRT) technique on NOAA's research and development WSR-88D in Norman, Oklahoma. The prototype algorithm incorporates a novel rule for the correct assignment of Doppler mean velocity that is needed to accommodate arbitrary stagger ratios. Description of the rule, consideration of errors, and choice of appropriate stagger ratios are presented. The staggered PRT algorithm is integrated with the standard processing on the WSR-88D, some details of which are included in the paper. A simple ground clutter canceller removes the pure complex time series mean (DC) component from autocovariance estimates; censoring of overlaid echoes and thresholding are equivalent to those used on the WSR-88D. Further, a cursory verification of statistical errors indicates good agreement with theoretical expectations. Although the staggered PRT algorithm operates in real time, it was advantageous to collect several events of staggered PRT time series data for further scrutiny. Results presented from one of the events demonstrate the potency of the staggered PRT to mitigate range and velocity ambiguities.
Observed failure modes of the WSR-88D velocity dealiasing algorithm during severe weather outbreaks
2009
The current WSR-88D Velocity Dealiasing Algorithm (VDA) has been in place without significant changes for a number of years (Eilts and Smith, 1990). It has proved itself to be a robust and reliable algorithm for producing operationally useful output. An ongoing, study at the Radar Operations Center suggests that the long-term failure rate for the algorithm is somewhere between 1% and 2% (Bob Lee, private communication). Algorithm performance remains good in clear-air and precipitation collection modes when the PRF used for velocity measurement is high enough to produce a reasonably large Nyquist co-interval (~+/25 m/s or larger). However, during some severe convective weather outbreaks, VDA failures have been noted. As part of the ROC/NSSL Technology Transfer MOU (Burgess and Fresch, 2006), multi-year tasks are in progress to 1) improve data quality, including enhancing the effective Nyquist co-interval, and 2) improve or replace the current VDA, improving overall and severe storm p...
2004
Proper censoring of contaminated or invalid data is essential for the National Weather Service (NWS) Weather Surveillance Radar – 1988 Doppler (WSR-88D) to be practical for forecasters and automated algorithms. The planned upgrade of the WSR-88D network to Open Radar Data Acquisition (ORDA) beginning in January 2005 will change radar processing and base data computation significantly, necessitating the development and fielding of new radar data censoring algorithms. Doppler radars have fundamental limits on the unambiguous range (ru) and unambiguous, or Nyquist, velocity (vN) resulting from the facts that both ru and vN are a function of pulse repetition frequency (PRF). The product ruxvN is equal to a constant, thus, changing the PRF to increase ru results in a decreased vN. At the wavelength of the WSR-88D (~10 cm) a single PRF with acceptable vN and ru at low elevation angles does not exist. Currently, the NWS uses a split cut scanning strategy at the lowest two elevation angles,...