nexrad tac meeting august 22-24, 2000 norman, ok ap clutter mitigation scheme cathy kessinger scott...
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NEXRAD TAC MeetingAugust 22-24, 2000
Norman, OK
AP Clutter Mitigation Scheme
Cathy Kessinger
Scott Ellis
Joseph VanAndel
http://www.atd.ucar.edu/rsf/NEXRAD/TAC_DQ_Aug00/index.html
August 23, 2000 Cathy Kessinger Slide 2
Ground clutter due to anomalouspropagation degradesthe performance of rainfall estimatesfrom radar
Currently, it must be detected by operators and clutterfilters turned onmanually
Automation!
Reflectivity RadialVelocity
ReflectivityAP Clutter
ReflectivityPrecipitation
August 23, 2000 Cathy Kessinger Slide 3
AP Clutter Mitigation Scheme
• Improve quality of rainfall estimates
• 4 CCR’s have been approved
• Preliminary implementation of the AP clutter detection algorithm is underway at OSF
• Planned implementation for Open Build 2
August 23, 2000 Cathy Kessinger Slide 4
AP Clutter Mitigation Scheme• Automatic clutter filter control
• Radar Echo Classifier– Uses fuzzy logic techniques
(for details, see http://www.atd.ucar.edu/rsf/NEXRAD/index.html)
– AP Detection Algorithm (APDA)– Precipitation Detection Algorithm (PDA)– Clear Air Detection Algorithm (CADA)– other algorithms, as needed
• Reflectivity compensation of clutter filter bias
• Tracking of clutter filtered regions
August 23, 2000 Cathy Kessinger Slide 5
Radar Echo Classifier
• Tim O’Bannon is implementing REC – AP clutter detection algorithm is first– Sharing NEXRAD data sets for testing– Working out methods of comparing results
between NCAR and OSF
August 23, 2000 Cathy Kessinger Slide 6
Evaluation of REC• Use statistical indices to measure
performance of algorithms against “truth”– CSI, POD, FAR computed from
2x2 contingency table
• For NEXRAD cases, truth defined by human experts (subjective)
• For S-Pol cases, truth defined by Particle Identification algorithm (objective)
August 23, 2000 Cathy Kessinger Slide 7
Radar Echo Classifier
• Objective truth fields with S-Pol added– Truth derived from Particle Identification algorithm
using multi-parameter fields as input – No human truthing– Improves algorithm optimization– Lower FAR realized for APDA for S-Pol cases
• Less improvement for NEXRAD cases (subjective truth)
– Allows for real-time statistical evaluation
August 23, 2000 Cathy Kessinger Slide 8
Example of S-Pol “truth”
• 11 February 1999• AP, clear air &
precipitation• Truth:
– green = AP
– gold = precipitation
– red = clear air
Reflectivity Radial Velocity
Spectrum Width Truth
August 23, 2000 Cathy Kessinger Slide 9
Radar Echo Classifier• Two reflectivity features added
– Both computed over a local area– Matthias Steiner “spin” variable
• Reflectivity difference from gate to gate > threshold
• Difference > 0, spin > 0; Difference <0, spin <0
• Percentage of maximum possible spin changes
• Sign =100 for “speckled” fields, 0 for pure gradients
– Tim O’Bannon “sign” variable• Reflectivity difference from gate to gate
• Accumulate + or -1 depending on sign of difference
• Sign=0 for “speckled” fields, +1 for pure gradients
August 23, 2000 Cathy Kessinger Slide 10
Radar Echo Classifier
• Evaluating APDA in non-Doppler region (430 km) – Using spin and sign with reflectivity “texture”
and vertical difference in reflectivity – Membership functions are not optimized– KNQA movie loop
August 23, 2000 Cathy Kessinger Slide 11
Radar Echo Classifier• New Python Environment for Radar
Processing (PERP)– Better software development environment– Debugging nearly done– Implemented Radar Echo Classifier on S-Pol
• Web-based display of REC output (http://www.atd.ucar.edu/rsf/STEPS/AP/index.html)
• Real-time operation during STEPS
• Continue development during IMPROV this winter
August 23, 2000 Cathy Kessinger Slide 12
PrecipitationDetection Algorithm
Clear AirDetection Algorithm
Particle Identification(truth)
APDetection Algorithm
Radial VelocityReflectivity
Movie loop of June 19
Movie loop of June 22
S-Pol real-time display of REC output
August 23, 2000 Cathy Kessinger Slide 13
Radar Echo Classifier
• Development continuing on – Precipitation Detection Algorithm– Clear Air Detection Algorithm
August 23, 2000 Cathy Kessinger Slide 14
Reflectivity
FY99 PDA
Truth
FY98 CPDA
Precipitation Detection Algorithm
S-Pol scan with convective and stratiform precipitation (gold), clutter (green) and clear air return (red)
Note improved detection of all precipitation regions with PDA vs CPDA
CPDA is very good at detecting noise
August 23, 2000 Cathy Kessinger Slide 15
CADA Truth
CADA Truth
Clear Air Detection Algorithm
Results shown from two of the S-Pol cases
CADA performs well at detecting the clear air and does not detect most of the clutter return
Edges of precipitation echoes are falsely detected
August 23, 2000 Cathy Kessinger Slide 16
Summary• Implementation of REC at OSF is primary
emphasis
• Continuing to develop REC algorithms– Sea clutter algorithm next
• Next fiscal year NCAR will: – Add reflectivity compensation to PERP– Start development of automatic clutter filter
control