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NEXRAD Data Quality Optimization AP Clutter Mitigation Scheme. Cathy Kessinger Scott Ellis, Joe Van Andel, John Hubbert, Greg Meymaris, Mike Dixon. Research Applications Laboratory/ Earth Observing Systems. AP Clutter Mitigation Scheme.

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slide1

NEXRAD Data Quality Optimization

AP Clutter Mitigation Scheme

Cathy Kessinger

Scott Ellis, Joe Van Andel, John Hubbert, Greg Meymaris, Mike Dixon

Research Applications Laboratory/ Earth Observing Systems

NEXRAD TAC Meeting

ap clutter mitigation scheme
AP Clutter Mitigation Scheme
  • Objective -- automatic detection and suppression of AP clutter to improve hydrology and aviation products for the WSR-88D
  • Approach:
    • Separate clutter from precipitation return using the Radar Echo Classifier (REC)
      • AP Clutter Detection Algorithm (REC-APDA)
      • Precipitation Detection Algorithm (REC-PDA)
    • Current: remove clutter gates during RPG processing
    • Future: Transition REC to ORDA and remove clutter in spectral domain

NEXRAD TAC Meeting

orpg radar echo classifier rec
ORPG Radar Echo Classifier (REC)
  • REC-APDA classifies return from clutter
  • REC-PDA classifies return from precipitation
  • Fuzzy logic, data fusion algorithms
    • Independent from each other
    • Moment data (Z, V, W) are input
    • Likelihood field is output (0-100%)
  • Run in RPG
    • REC-APDA deployed Fall 2002
    • REC-PDA to be deployed in future

NEXRAD TAC Meeting

ap clutter mitigation scheme1
AP Clutter Mitigation Scheme
  • Enhanced Precipitation Preprocessor (EPRE)
    • Builds the Hybrid Scan Reflectivity (HSR) for input into radar-derived rainfall algorithm
    • REC-APDA used as quality control (QC) for clutter
    • If clutter detected (REC-APDA>50%), next elevation angle used for HSR

NEXRAD TAC Meeting

modification to epre qc
Modification to EPRE QC
  • Installed ORPG Common Operating Development Environment (CODE) at NCAR
    • REC-PDA ported to CODE
    • EPRE modified
      • QC does extra check w/ REC-PDA
      • For gate to be rejected it must:
        • Be clutter (REC-APDA > 50%), OR
        • Not be precipitation (REC-PDA < 50%)
  • Have run a few, selected cases using this new QC
    • Results look very favorable
    • More testing needed

NEXRAD TAC Meeting

rec apda and rec pda results
REC-APDA and REC-PDA results

Radial velocity

Reflectivity

AP clutter

REC-PDA

REC-APDA

  • St. Louis KLSX
    • 1 Nov 2004
  • Note:
    • REC-APDA finds clutter
    • REC-PDA finds precipitation (not clutter)

NEXRAD TAC Meeting

rec apda and rec pda results1
REC-APDA and REC-PDA results

Radial velocity

Reflectivity

  • In mixed clutter and precipitation cases,
    • REC-APDA gives a missed detection (REC-APDA<50%)
    • REC-PDA does not classify it as precipitation (REC-PDA<50%)
  • 2nd QC check for EPRE
    • Better HSR results
  • Recall, for gate to be rejected it must:
    • Be clutter (REC-APDA > 50%)
    • OR
    • Not be precipitation (REC-PDA < 50%)

Clutter mixed with weather

REC-APDA

REC-PDA

NEXRAD TAC Meeting

hsr using only rec apda
HSR using only REC-APDA

NEXRAD TAC Meeting

summary of rpg rec
Summary of RPG REC
  • Adding REC-PDA to EPRE quality control checks will improve quality of Hybrid Scan Reflectivity

NEXRAD TAC Meeting

migration from rpg into orda
Migration from RPG into ORDA

a) Old ORPG-based Scheme

ORPG

LegacyRDA

I & Q

Moments

Products

REC

AP Clutter Control

b) New ORDA-based Scheme

ORDA

Corrected Moments

Products

ORPG

REC

Uncorrected

Moments

I & Q

REC

SZ Alg.

(NP Clutter)

REC

Spectral Variables

Clutter or

Precipitation

AP Clutter Control

  • ORDA allows spectral processing techniques
  • Moving REC-APDA to ORDA will allow clutter filter control – only filter the clutter targets, not precipitation
  • Preliminary Spectral REC-APDA coded

NEXRAD TAC Meeting

Result: Stratiform precipitation is retained!!

spectral variables in rec
Spectral Variables in REC

Clutter

Precipitation

g-i

g-3

g-2

g-1

g0

g1

g2

g3

g+i

  • With ORDA, input spectral domain variables into REC
    • Variables under test include:
      • F(gi) = power at the gi velocity index
      • Cp = ∑ [F(g0) + F(g-1) + F(g+1)] (power at 0th coefficient, blue region)
      • Pnz = ∑ [F(g-3) + F(g-2) + F(g+2) + F(g+3)] (power near 0th coefficient, green region)
      • Ptot = ∑ F(gi) where i = -n to +n (total power, summation of all gi)
      • Ratio 1 = Cp/(Ptot – Cp)
      • Ratio 2 = Cp/Pnz

NEXRAD TAC Meeting

ratios 1 and 2
Ratios 1 and 2

Reflectivity

Radial Velocity

Precipitation

NP Clutter

Ratio 1

Ratio 2

  • Definitions:
    • Ratio 1 = Cp/(Ptot – Cp)
    • Ratio 2 = Cp/Pnz
  • Precipitation has values near zero
  • Clutter has high values
  • Membership functions devised for APDA and ran through REC
  • Comparison made:
    • Original APDA (without SW field)
    • Adding Ratio1 and 2 as additional feature fields
    • Adding Ratio 1 and 2 and removing the VE and SDVE feature fields

NEXRAD TAC Meeting

high mag of previous slide
High Mag of Previous Slide

APDA + Ratio1 + Ratio2

No Doppler

Original APDA

(no SW)

APDA + Ratio1 + Ratio2

Velocity

Power

  • Blue oblongs: precipitation only
  • Red oblongs: clutter only
  • Adding spectral variables improves the APDA performance
    • Discrimination between precipitation return and clutter is improved

NEXRAD TAC Meeting

spectral rec apda
Spectral REC-APDA
  • Preliminary version of Spectral REC
  • Uses same feature fields as ORPG REC-APDA
    • Spectral variables will be added soon
    • Local area is 2 beams on either side, 8 gates long
  • In the example shown in following slides, the clutter filter is enabled only where the REC-APDA identifies the echo as clutter or mixed clutter and precipitation
    • Purely precipitation echoes are not clutter-filtered

NEXRAD TAC Meeting

unfiltered moment data s pol at marshall co
Unfiltered Moment Data: S-Pol at Marshall, CO
  • Time series data collected on March 28, 2004
  • Low PRF (320 Hz), gate spacing 225 m, 0.5 deg elevation

Zero m/s

Mixed

Mixed

Mixed

Zero m/s

NEXRAD TAC Meeting

Reflectivity

Radial Velocity

Spectrum Width

filtered moment data s pol at marshall co
Filtered Moment Data: S-Pol at Marshall, CO
  • Spectral REC-APDA identifies clutter
  • GMAP removes it

Zero m/s

Mixed

Mixed

Mixed

Zero m/s

NEXRAD TAC Meeting

Reflectivity

Radial Velocity

Spectrum Width

summary
Summary
  • Moving the REC-APDA to the ORDA allows:
    • Spectral variables to be used
    • Provides better clutter/precipitation discrimination
    • Better preserve stratiform precipitation near zero m/s
    • Clutter filter only applied to clutter and mixed clutter/precipitation echoes
      • Filters not applied to purely precipitation echoes

NEXRAD TAC Meeting