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Dual-Pol Radar Data: A Brief Primer
and A Few Brief Pseudo-Operational Exercises
Dual-Pol Radar Data: A Brief Primer
and A Few Brief Pseudo-Operational Exercises
(Courtesy of)
Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota
(Courtesy of)
Dan MillerScience and Operations OfficerNWS/WFO Duluth, Minnesota
NWS Grand Rapids, MI
Spring 2011 media seminar 19 March 2010
What Will Be New with Dual-Pol?What Will Be New with Dual-Pol?
Same VCPs10 cm Wavelength1.2 degree effective beam widthReflectivity/ Velocity/ Spectrum Width
unchanged
Same VCPs10 cm Wavelength1.2 degree effective beam widthReflectivity/ Velocity/ Spectrum Width
unchanged
New Products:Differential Reflectivity (ZDR)Correlation Coefficient (CC)Specific Differential Phase (KDP)Melting Layer (ML)Hydrometeor Classification (HC)Quantitative Precipitation Estimation (QPE) (9 Products)
New Products:Differential Reflectivity (ZDR)Correlation Coefficient (CC)Specific Differential Phase (KDP)Melting Layer (ML)Hydrometeor Classification (HC)Quantitative Precipitation Estimation (QPE) (9 Products)
Why Upgrade to Dual-Pol?Why Upgrade to Dual-Pol?
SoftballsSoftballs
Peas
Quarters/Golf Balls
Quarters/Golf Balls
Peas/Torrential Rain
Peas/Torrential Rain
GrapefruitGrapefruit Quarters 4 inches deep
Quarters 4 inches deep
PenniesPennies
Thunderstorm examplesThunderstorm examples
Why Upgrade to Dual-Pol?Why Upgrade to Dual-Pol?
Aurora, NE
Supercell
6/22/2003
Aurora, NE
Supercell
6/22/2003
Giant Hail examplesGiant Hail examples
Vivian, SD
Supercell
7/23/2010
Vivian, SD
Supercell
7/23/2010
Why Upgrade to Dual-Pol?Why Upgrade to Dual-Pol?
8 May 20038 May 2003 9 May 20039 May 2003
Supercell Hydrometeor Distribution
Supercell Hydrometeor Distribution
Why Upgrade to Dual-Pol?Why Upgrade to Dual-Pol?Winter Storm ExamplesWinter Storm Examples
Melting Layer: Mixed precip
Melting Layer: Mixed precip
Wet Aggregates: 3 Inch/hour Snowfall
Rates
Wet Aggregates: 3 Inch/hour Snowfall
Rates
Radar Sampling: The Dirty DetailsRadar Sampling: The Dirty Details
Raindrops fall as oblate spheriods
Raindrops fall as oblate spheriods
Power Return is
proportional to ∑ n6
Power Return is
proportional to ∑ n6
Hydrometeor size/phase and fall speed diverstiy
Hydrometeor size/phase and fall speed diverstiy
Dual-Pol Radar BasicsDual-Pol Radar BasicsPulse Transmit/Receive
SchematicPulse Transmit/Receive
Schematic
Dual-Pol Radar BasicsDual-Pol Radar BasicsWSR-88DPulse Transmit/Receive
SchematicWSR-88DPulse Transmit/Receive
Schematic
Transmit Pulse polarized at 45 degree angle
Transmit Pulse polarized at 45 degree angle
Receive and Process the returned vertically and horizontally returned power separately
Receive and Process the returned vertically and horizontally returned power separately
Looking “Down Beam”Looking “Down Beam”
Differential Reflectivity (ZDR)Differential Reflectivity (ZDR)
Simply a ratio of returned horizontal to vertical power
Simply a ratio of returned horizontal to vertical power
vv
hhDR Z
ZZ 10log10
Differential Reflectivity (ZDR)Differential Reflectivity (ZDR)
• ZDR > 0 ZDR > 0 Horizontally- Horizontally-oriented mean profileoriented mean profile
• ZDR < 0 ZDR < 0 Vertically- Vertically-oriented mean profileoriented mean profile
• ZDR ~ 0 ZDR ~ 0 Near- Near-spherical mean profilespherical mean profile
Eh
Ev
Eh
Ev
Eh
Ev
Differential Reflectivity (ZDR)Differential Reflectivity (ZDR)
Differential Reflectivity (ZDR)Differential Reflectivity (ZDR)
Typical Data Ranges for ZDRTypical Data Ranges for ZDR
Correlation Coefficient (CC)Correlation Coefficient (CC)
How similarly the horizontally and vertically polarized backscattered energy are behaving within a resolution volume for Rayleigh scattering
How similarly the horizontally and vertically polarized backscattered energy are behaving within a resolution volume for Rayleigh scattering
2/122/12
*
)0(
vvhh
hhvv
HV
SS
SS
ThinkThink Spectrum Width for Spectrum Width for HydrometeorsHydrometeorsTMTM
ThinkThink Spectrum Width for Spectrum Width for HydrometeorsHydrometeorsTMTM
Excellent discriminator for the presence of mixed hydrometeor phases and/or non-meteorological echoes
Excellent discriminator for the presence of mixed hydrometeor phases and/or non-meteorological echoes
Correlation Coefficient (CC)Correlation Coefficient (CC)
Correlation Coefficient (CC)Correlation Coefficient (CC)
Typical Data Ranges for CC - note color table is logarithmic
Typical Data Ranges for CC - note color table is logarithmic
Differential Phase (ΦDP)Differential Phase (ΦDP)
Measure of the phase difference between horizontal and vertical polarized pulses: Propagation Effect
Measure of the phase difference between horizontal and vertical polarized pulses: Propagation Effect
VHDP
Differential Phase (ΦDP)Differential Phase (ΦDP)
RainRain
Rain + Hail
Rain + Hail
Heavy Rain
Heavy Rain
Specific Differential Phase (KDP)Specific Differential Phase (KDP)
Simply the Range Derivative of Differential Phase
Simply the Range Derivative of Differential Phase
Immune to partial (< 40%) beam blockage, attenuation, calibration, presence of hail
12
12
2)()(
rrrr
K DPDP
DP
Excellent indicator of liquid water hydrometeor content within sample volume
Specific Differential Phase (KDP)Specific Differential Phase (KDP)
ΦDPΦDP KDPKDP
Specific Differential Phase (KDP)Specific Differential Phase (KDP)
Typical Data Ranges for KDPTypical Data Ranges for KDP
What Will Be New with Dual-Pol?What Will Be New with Dual-Pol?
Biggest fundamental change to our most critical warning decision-making dataset since the advent of the WSR-88D network 15-20 years ago
Biggest fundamental change to our most critical warning decision-making dataset since the advent of the WSR-88D network 15-20 years ago
New dual-pol base moment CANNOT be used in a vaccum! They MUST be used in complement with each other (similar to spectrum width now)
New dual-pol base moment CANNOT be used in a vaccum! They MUST be used in complement with each other (similar to spectrum width now)
Pseudo-Operational Case Examples:
You Determine the Hydrometeor Type
Pseudo-Operational Case Examples:
You Determine the Hydrometeor Type
Exercise 1Exercise 1
Z:65-70 dBz45-50 dBz
Z:65-70 dBz45-50 dBz
CC:0.92-0.970.97-1.00
CC:0.92-0.970.97-1.00
KDP:3-6 deg/km5-7 deg/km
KDP:3-6 deg/km5-7 deg/km
ZDR:0 to 1 dBz4 to 7 dBz
ZDR:0 to 1 dBz4 to 7 dBz
Exercise 1: SummaryExercise 1: SummaryBlue: Heavy Rain and Hail (shedding
drops/large hail?)Blue: Heavy Rain and Hail (shedding
drops/large hail?)White: Torrential Rain (big drops?)White: Torrential Rain (big drops?)
Exercise 2Exercise 2
Z:50-55 dBz
Z:50-55 dBz
ZDR: 1.5-3 dBz
ZDR: 1.5-3 dBz
CC:> 0.98CC:
> 0.98KDP:
2-3 deg/kmKDP:
2-3 deg/km
Exercise 2: Summary Very Heavy RainExercise 2: Summary Very Heavy Rain
Z:50-55 dBz
Z:50-55 dBz
ZDR: 1.5-3 dBz
ZDR: 1.5-3 dBz
CC:> 0.98CC:
> 0.98KDP:
2-3 deg/kmKDP:
2-3 deg/km
Exercise 2: SummaryExercise 2: Summary
KDPKDP Instantaneous Rainfall RateInstantaneous Rainfall Rate
Exercise 3Exercise 3Z: 8-18 dBzZ: 8-18 dBz
ZDR: Wide RangeZDR: Wide Range CC: 0.50 to 0.70CC: 0.50 to 0.70
Φ: slow increase with rangeΦ: slow increase with range
Exercise 3: SummaryExercise 3: SummaryBirds and Insects: Key is exceptionally
low CC valuesBirds and Insects: Key is exceptionally
low CC values
ZZ
VV SWSW
CCCC
Exercise 4Exercise 4
Z: 35-45 dBzZ: 35-45 dBz ZDR: +2 to +5 dBzZDR: +2 to +5 dBz CC: 0.65 to 0.85CC: 0.65 to 0.85
Exercise 4: SummaryExercise 4: Summary
2141 UTC2141 UTC
AA
ZZ ZDRZDR ρHVρHV
Rain/Snow/Sleet MixRain/Snow/Sleet Mix
2333 UTC2333 UTC
BB
ZZ ZDRZDR ρHVρHV
2 hours later: all heavy snow (diabatic cooling effects + FGEN)
2 hours later: all heavy snow (diabatic cooling effects + FGEN)
Exercise 5Exercise 5
Z: 5-20 dBzZ: 5-20 dBz CC: 0.40 to 0.55CC: 0.40 to 0.55ZDR: Wide RangeZDR: Wide Range
Exercise 5: SummaryExercise 5: SummaryChaff: Key is exceptionally low CC valuesChaff: Key is exceptionally low CC values
Reflectivity
Correlation Coefficient Hydrometeor Classification
Differential Reflectivity
Thank You!Thank You!
ReferencesDual-Polarization Radar Training for NWS Partners
http://www.wdtb.noaa.gov/courses/dualpol/Outreach/index.html
Dual Polarization Quick Training Aidhttp://www.wdtb.noaa.gov/courses/dualpol/trainingaid/
index.htm
ReferencesDual-Polarization Radar Training for NWS Partners
http://www.wdtb.noaa.gov/courses/dualpol/Outreach/index.html
Dual Polarization Quick Training Aidhttp://www.wdtb.noaa.gov/courses/dualpol/trainingaid/
index.htm