Weather radar signal processing techniques

Super Resolution for the NEXRAD Network

Legacy-resolution base data on the NEXRAD network consists of reflectivity on a 1 km-by-1 deg polar grid and Doppler velocity and spectrum width on a similar 250 m-by-1 deg grid. It has been shown that some meteorological signatures can be detected at greater ranges using radar data with finer spatial resolution on a 250 m-by-0.5 deg grid. Radar data produced this way is termed super-resolution data. Super-resolution radar data has the potential to increase the detection range of mesocyclone and tornado vortex signatures as well as increase the visibility of reflectivity signatures associated with severe weather. These can contribute toward an increase in warning times for severe thunderstorms and tornadoes. Super-resolution has been available across the NEXRAD network since 2008.

As part of this project, we completed the development of a super-resolution radial recombination algorithm. This algorithm is fundamental for this project because it allows legacy-like resolution data to be fed to ORPG algorithms when operating in the super-resolution mode. The recommended super-resolution radial recombination algorithm was transferred to the National Weather Service (NWS) Radar Operations Center (ROC) for operational implementation. This implementation was carefully validated with our prototype to ensure the operational version of the algorithm performed as designed.

In close cooperation with the ROC Applications Branch, we also analyzed the effects of feeding recombined base data to the ORPG algorithms. We employed an off-line ORDA playback system to process numerous hours of time-series data. By statistically comparing base data moments obtained from processing the same data sets using the legacy and super-resolution modes of operation, we assessed the effectiveness of the radial recombination algorithm.

If you would like to learn some of the technical details behing this technique, you can download my ERAD (2006) and AMS (2007) conference papers.

A paper evaluating the impact of super-resolution on the WSR-88D's ability to detect low-level mesocyclones was presented at the 25th Severe Local Storms conference and is about to be published in the AMS Journal of Weather and Forecasting.

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