dual-pol radar data: a brief primer and a few brief pseudo-operational exercises (courtesy of) dan...

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


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


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


• 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


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


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


ΦDPΦDP KDPKDP


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?)


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


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)


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


Dual Polarization Quick Training Aidhttp://www.wdtb.noaa.gov/courses/dualpol/trainingaid/

index.htm





dual-pol radar data: a brief primer and a few brief pseudo-operational exercises (courtesy of) dan...

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