Hydrometeorology and Hydrometeorology and Polarimetric Radar Polarimetric Radar

How can Polarimetric radar aid in How can Polarimetric radar aid in flash flood forecasting? flash flood forecasting?

James J. Stagliano, JrJames J. Stagliano, Jr.1,.1, James L. Alford James L. Alford11, , Dean NelsonDean Nelson11, J. William Conway, J. William Conway22, ,

Barbara GibsonBarbara Gibson33 and Don Hyde and Don Hyde33

11Enterprise Electronics CorporationEnterprise Electronics Corporation22Weather Decision TechnologiesWeather Decision Technologies

33Choctawhatchee, Pea and Yellow Rivers Watershed AuthorityChoctawhatchee, Pea and Yellow Rivers Watershed Authority

OutlineOutline

Failure of RadarFailure of Radar Promise of Polarimetric Weather RadarPromise of Polarimetric Weather Radar Choctawhatchee, Pea, Yellow Rivers Choctawhatchee, Pea, Yellow Rivers

WatershedWatershed EEC Polarimetric Weather RadarEEC Polarimetric Weather Radar ConclusionConclusion

Failure of RadarFailure of Radar

Numerous meteorological and physical effects Numerous meteorological and physical effects limit accurate rainfall estimationlimit accurate rainfall estimation– Marshall – Palmer (Z-R) RelationshipMarshall – Palmer (Z-R) Relationship

Different DSD Different DSD Varies from event to event Varies from event to event Different DSD Different DSD Varies within precipitation event Varies within precipitation event Mie Resonance EffectsMie Resonance Effects

– Hail ContaminationHail Contamination– Beam BlockageBeam Blockage– AttenuationAttenuation– Nonuniform beam fillingNonuniform beam filling– Height Above GroundHeight Above Ground

Wind dispersionWind dispersion Precipitation Type (Melting Layer)Precipitation Type (Melting Layer)

Failure of Radar to DeliverFailure of Radar to Deliver

Radar – Precipitation EstimationRadar – Precipitation Estimation

Rainfall Estimates given by Marshall-Palmer Rainfall Estimates given by Marshall-Palmer RelationshipRelationship

– Dependent on sixth power of diameterDependent on sixth power of diameter

Drop SizeDrop Size QuantityQuantity ZZ Water VolumeWater Volume

1 mm1 mm 40964096 36 dBZ36 dBZ 17,160 mm17,160 mm33

4 mm4 mm 11 36 dBZ36 dBZ 270 mm270 mm33

A factor of 63 difference

baRz

Radar – Drop Size DistributionRadar – Drop Size Distribution

Similar Reflectivity, Different Drop Size Distributions

ScatteringScattering

Precipitation ScatteringPrecipitation Scattering

Assumption is all scattering is RayleighAssumption is all scattering is Rayleigh– True for S bandTrue for S band– Not true for C and X band (Ryzhkov, 2005)Not true for C and X band (Ryzhkov, 2005)

C-band:

= 5.33 cm

Mie ~ 4.5 mm 53.0 2

a

X-band:

= 3.0 cm

Mie ~ 2.5 mm 53.0 2

a

Polarimetric Weather RadarPolarimetric Weather Radar

Transmits microwave energy in both Transmits microwave energy in both horizontal and vertical polarizationshorizontal and vertical polarizations– Able to measure entire scattering matrixAble to measure entire scattering matrix– Much more information of scattering mediumMuch more information of scattering medium

Standard Base Moments: ZStandard Base Moments: ZHH, V, VHH, W, WHH

Polarimetric Base Moments : ZPolarimetric Base Moments : ZDRDR, , DPDP, , HVHV, L, LDRDR

– Estimate the average Drop Size DensityEstimate the average Drop Size Density– Identify average particle shape Identify average particle shape Hydrometeor Classification Hydrometeor Classification– Immunity from beam blockageImmunity from beam blockage– Variables change due to rainfall Variables change due to rainfall Much better rainfall Much better rainfall

estimationsestimations

Conventional Weather RadarConventional Weather Radar

Polarimetric RadarPolarimetric Radar

And Vertical Pulse

Polarimetric Weather RadarPolarimetric Weather Radar

Enhanced SIDPOLTM (2 Patents Granted to EEC)

Vertical cross-sections of radar variables and results of classification.

NCAR Spol radar. August 14, 1998. Florida

LR – light rain, MR – moderate rain, HR – heavy rain, LD – large drops, R/H – rain / hail mixture, GSH – graupel / small hail, HA – hail, DS – dry snow, WS – wet snow, IH – horizontally oriented crystals, IV – vertically oriented crystals

Polarimetric Weather RadarPolarimetric Weather Radar

Raindrops are oblate spheroidsRaindrops are oblate spheroids

Horizontal Returns greater than vertical returnsHorizontal Returns greater than vertical returns Phase shift in horizontal is more than in vertical Phase shift in horizontal is more than in vertical

DPDP increases with range through rain increases with range through rain

Polarimetric RainratePolarimetric Rainrate

(Doviak and Zrnic, 1993)

Polarimetric RainRate (KPolarimetric RainRate (KDPDP))

12

12

22 rr

rr

r

rK DPDPDPDP

Specific Differential Propagation Phase

• Independent of receiver/transmitter calibration

• Independent of attenuation

• Less sensitive to variations of size distributions (compared to Z)

• Immune to particle beam blocking

• Unbiased if rain is mixed with spherical hail

• Noisy at low rainrates

Radar RainRateRadar RainRatebb zaRaRz

bDPKaR

DRaZbDPKcR 1.010

DRaZbhZcR 1.010

Marshall - Palmer

KDP

Zh - ZDR

KDP - ZDR

Polarimetric Radar vs. GaugePolarimetric Radar vs. Gauge

(Bringi and Chandrasekar, 2001)

Polarimetric Weather RadarPolarimetric Weather RadarRainfall MeasurementsRainfall Measurements

“Traditional” R(Z) estimate Polarimetric R(KDP) estimatebzaR bDPKaR

Polarimetric Radar and RainfallPolarimetric Radar and Rainfall

One hour point measurements: Radar estimates vs. gages

Areal Mean Rain Rate BiasAreal Mean Rain Rate Bias

Hail

Choctawhatchee, Pea, Yellow Rivers Choctawhatchee, Pea, Yellow Rivers WatershedWatershed

HistoryHistory 1990 – Watershed Authorities created throughout state1990 – Watershed Authorities created throughout state

– After devastating Elba Flash FloodsAfter devastating Elba Flash Floods– CPYRWA only active authorityCPYRWA only active authority

SE AL SE AL only region in the state with extensive data on its water only region in the state with extensive data on its water resources and needsresources and needs

– Initially just Choctawhatchee – Pea RiversInitially just Choctawhatchee – Pea Rivers– Started with 3 rain gaugesStarted with 3 rain gauges

1994 - COE Installed Network of Stage and Rain Gauges1994 - COE Installed Network of Stage and Rain Gauges 1997 – Yellow River Added1997 – Yellow River Added 1998 – Major Flood1998 – Major Flood 2005 – Conecuh River under consideration2005 – Conecuh River under consideration

Choctawhatchee, Pea, Yellow Rivers Choctawhatchee, Pea, Yellow Rivers WatershedWatershed

EEC C-Band Polarimetric RadarEEC C-Band Polarimetric Radar TransmitterTransmitter

– 1 MW 1 MW Split between channelsSplit between channels

– 500 kW per channel500 kW per channel

– Magnetron Magnetron Coherent on ReceiveCoherent on Receive

– PW 0.4, 0.8, 2.0 PW 0.4, 0.8, 2.0 ss– PRF 300 – 2000 HzPRF 300 – 2000 Hz

EDRP-9 Signal ProcessorEDRP-9 Signal ProcessorIntermediate Frequency 60.00 MHzDigitization rate 80 MHzLinear dynamic range >100 dBMinimum discernable signal <110 dBClutter suppression >50 dBRange resolution >45 metersPRF <250 Hz to >1300 HzPhase noise <-53 dBc integrated over the

Nyquist co-interval

Greatly Improved AccuracyGreatly Improved Accuracy

–Precipitation Estimates Improved Precipitation Estimates Improved Up to 40%Up to 40%

SidPolSidPolTMTM Radar is Now a True Radar is Now a True Hydrological InstrumentHydrological Instrument

–Better Clutter Identification and Better Clutter Identification and EliminationElimination

–True Precipitation ClassificationTrue Precipitation Classification

IceIce

SnowSnow

HailHail

Liquid RainLiquid Rain

EEC EEC C-Band Polarimetric RadarC-Band Polarimetric Radar

2 Installed2 Installed– UK Met (250 kW)UK Met (250 kW)– EEC (1 MW)EEC (1 MW)

2 more installations this year2 more installations this year– Valpraiso University (Indiana, USA) (1 MW)Valpraiso University (Indiana, USA) (1 MW)– Austria (250 kW)Austria (250 kW)

Hydrological Modelling - HDSSHydrological Modelling - HDSS

QPE-SUMSQPE-SUMS– Multiple sensor integration for quantitative Multiple sensor integration for quantitative

precipitation estimationprecipitation estimation– Accurate estimates of rainfallAccurate estimates of rainfall

Basin accumulation to forecast flood riskBasin accumulation to forecast flood risk

Alabama ConsortiumAlabama Consortium Statewide ConsortiumStatewide Consortium

– UniversitiesUniversities University of South AlabamaUniversity of South Alabama University of Alabama - HuntsvilleUniversity of Alabama - Huntsville Auburn UniversityAuburn University University of Alabama - TuscaloosaUniversity of Alabama - Tuscaloosa

– Federal AgenciesFederal Agencies NASANASA

– State Agencies State Agencies Watershed Management AuthoritiesWatershed Management Authorities State EMAState EMA

– Local AgenciesLocal Agencies County EMA’sCounty EMA’s Local First RespondersLocal First Responders

– EECEEC

Integration Research LaboratoryIntegration Research Laboratory Fully integrated and Fully integrated and

operational operational hydrometeorological hydrometeorological forecasting centerforecasting center

Located at EECLocated at EEC Operational testbed for new Operational testbed for new

technologytechnology Data freely shared with Data freely shared with

consortium partnersconsortium partners

– All data streams integratedAll data streams integrated SatelliteSatellite RadarRadar AWS sensorsAWS sensors NWPNWP

– Integration Integration SensorsSensors SoftwareSoftware CommunicationsCommunications TrainingTraining

– Evaluation Evaluation SensorsSensors SoftwareSoftware CommunicationsCommunications

Future WorkFuture Work

TropicalTropical– ConvectiveConvective

Hail shaftsHail shafts Large DropsLarge Drops More attenuationMore attenuation

– HurricanesHurricanes

Run-off ModelingRun-off Modeling AL NetworkAL Network

– Hurricane DissipationHurricane Dissipation

ExtraTropicalExtraTropical– StratiformStratiform

BrightbandBrightband Smaller DropsSmaller Drops

– Snow / IceSnow / Ice

Run-off ModelingRun-off Modeling

South Alabama Valpariso, Indiana