Initial Implementation of Super-Resolution Data on the NEXRAD Network Dr. Sebastian Torres CIMMS/NSSL A presentation to the Data Quality Team June 15, 2007

2 What is Super Resolution? Legacy (existing) Resolution spatial sampling –Reflectivity: 1-km by 1-deg grid –Doppler: 250-m by 1-deg grid Super Resolution spatial sampling –All moments: 250-m by 0.5-deg grid Finer spatial sampling and smaller resolution volume lead to about 50% improvement in range of detection for mesocyclone and tornado signatures (Brown et al. 2002) Tornado outbreak in Oklahoma City 9 May 2003 (Curtis et al. 2003) Legacy ResolutionSuper Resolution Two elements of super-resolution data

3 Super Resolution for NEXRAD Super-resolution data scheduled for operational use on NEXRAD –Short-term goals - Phase I (ORDA Build 10) Data used for visualization only Produce legacy- and super-resolution data streams –ORPG algorithms ingest legacy-resolution data Super-resolution data produced on lower-elevation scans –Higher likelihood of finding tornado signatures –Long-term goals - Phase II (ORDA Build >12?) Data used by the algorithms Produce super-resolution data stream only? –Not every algorithm may benefit from super-resolution data Elevation Azimuth ORDAORPG w v Z Products Signal Proc.Algorithms Super resolution base data ORDA

4 Characteristics of Super-Resolution Data Smearing due to antenna rotation is reduced using a data window Effective beamwidth is 25% narrower than with legacy resolution (Torres and Curtis 2006) –Better spatial resolution due to smaller resolution volume –Reduced data quality due to data windowing Errors of estimates are ~30% larger and NEXRAD Technical Requirements are not met 1 deg Legacy ResolutionSuper Resolution

5 Super Resolution Goals and Constraints Produce stronger signatures of mesocyclones and tornadoes Assure compatibility with current and future (planned) signal processing techniques Assure compatibility with current Volume Coverage Patterns (r a, v a, update times) Adhere to CPU load and bandwidth limitations Meet NEXRAD requirements for errors of estimates –Provide acceptable base data to algorithms

6 Super Resolution in the ORDA ORDA must produce base data with finer spatial sampling and resolution –Process overlapping 1-deg radials with data windowing sampled every 0.5 deg and no range averaging –For each range gate, M time-series data samples are weighted … with von Hann window if clutter filtering is not needed … with Blackman window if clutter filtering is needed 0 deg 0.5 deg 1.0 deg 1.5 deg 2.0 deg bypass filterbypass GCF Map 1 deg Pulse # M = 64

7 Super Resolution in the ORDA ORDA must produce unfolded reflectivity in the Doppler half of split cuts and must include the noise power in the metadata for the ORPG –This additional data are required in the ORPG to produce legacy-like data from super-resolution data ORDA must double the throughput –Processing pipeline is minimally affected, but there are twice the number of radials in a super- resolution data volume scan ORDA-ORPG transmission bandwidth must accommodate faster radial rates and additional data

8 Super Resolution in the ORPG ORPG algorithms expect data with legacy resolution and quality –Super-resolution data does not have the required resolution or quality for the algorithms –Must have both legacy and super-resolution data streams Two instances of the velocity dealiasing algorithm Radial recombination –Two super-resolution radials are recombined to form one legacy-resolution radial Z 14 Z 24 Z 11 Z 21 Z 12 Z 22 Z 13 Z 23 ZrZr 1 km 1 deg Super ResolutionLegacy Resolution vrvr 250 m v1v1 v2v2

9 Super Resolution in the ORPG The radial recombination algorithm assumes a bimodal Gaussian spectrum model Recombined data has legacy resolution and acceptable data quality –Recombined super- resolution data will not be exactly the same as the true legacy-resolution data v Doppler velocity v1v1 v2v2 Radial 1 PSD Radial 2 PSD Acceptable data quality

10 Super Resolution in the ORPG Radial recombination algorithm must deal with missing data and several special boundary conditions –Base data at the ORPG is censored and quantized! –Censoring can occur due to SNR thresholding or overlaid echoes Z 14 Z 24 Z 11 Z 21 Z 12 Z 22 Z 13 Z 23 ZrZr 1 km 1 deg ? Z BG Z BG is derived from a “best-guess” power (P BG ) 0 ≤ P BG < N SNR th

11 Super-Resolution Reflectivity KCRI March 19, 2006

12 Recombined Legacy-Resolution Reflectivity KCRI March 19, 2006

13 True Legacy-Resolution Reflectivity KCRI March 19, 2006

14 Summary Super Resolution data produces enhanced mesocyclone and tornado signatures –Potential to detect weaker and/or more distant tornadoes To meet long-term technical goals, NWS will implement and use Super Resolution with range oversampling techniques –Staged approach Build 10: –Recommended super resolution with azimuthal radial recombination Beyond Build 12: –Range oversampling techniques –Algorithms modified to ingest super-resolution data