Transcript Slide 1
Background The backscatter received on TWO KOUN transmits iseach EM pulse The WSR-88D at the National receive channels: The national WSR-88D network with an orientation “slanted” at a will Severe Storms Laboratory, KOUN, o 1) Receives backscatter with be to include polarimetric 45 upgraded angle to the horizontal surface. was upgraded addinpolarization electric fieldtooriented on capability beginning diversity in 2002. horizontal plane. approximately 2007. 2) Receives backscatter with electric field oriented on vertical plane. _/| KOUN Advantages of Polarimetric Radar • Better rainfall estimates • Ability to classify hydrometeor type • Better quality control of radar data New Polarimetric Radar Products Base Products Derived Products ZDR Differential Reflectivity R(syn) Rainfall estimation using ZH, ZDR, KDP rHV HCA Hydrometeor Classification Algorithm Cross-correlation coefficient FDP Differential phase shift KDP Specific differential phase shift Joint Polarization Experiment • Test engineering design of KOUN • Determine quality of KOUN data • Collect verification data sets for HCA and several experimental rainfall algorithms • Deliver and use KOUN data in WFO Norman • Obtain feedback from forecasters JPOLE Operational Demonstration at NWS Norman, Oklahoma Data delivery NWS Norman operations area - 9 May 2003 tornadoes Event driven May 2002 through March 2003 “Intense observation period” 19 April to 13 June 2003 “Overall, I think the (operational demonstration) was a wonderful success” – NWS Norman Forecaster Photos Courtesy: (L) Mike Magsig, CIMMS/WDTB; (R) Steve Kruckenberg, NOAA/NWS Norman, Oklahoma Differential Reflectivity (ZDR) Raindrop shapes in equilibrium Differential Reflectivity (ZDR) Differential Reflectivity (ZDR) Reflectivity (ZH) Differential Reflectivity (ZDR) Similar reflectivity, different drop size distributions! Hail !! Specific Differential Phase (KDP) • Is influenced by anisotropic hydrometeors • In heavy rain: better estimator of rates than ZH • Provides a good estimate of liquid water in a rain/hail mixture • Indicates the onset of melting • With ZH can detect hail Specific Differential Phase (KDP) Reflectivity (ZH) Specific Differential Phase (KDP) Heavy rain is apparently mixed with the hail. Cross-correlation Coefficient (rHV) Decreases in rHV may indicate: • Variety of hydrometeor types • Mixture of liquid and frozen hydrometeors • Hydrometeors with irregular shape • Wide distribution of hydrometeor orientation • Presence of large hail Cross-correlation Coefficient (rHV) SNOW ~0.85-1.00 CLUTTER ~0.5-0.85 CHAFF ~0.2-0.5 Reflectivity (ZH) Correlation Coefficient (rHV) Hydrometeor Classification Algorithm Partitions in the ZH, ZDR Space into Regions of Hydrometeor Types Hydrometeor Classification Algorithm Weighting Function for Moderate Rain WMR(ZH, ZDR) Hydrometeor Classification Algorithm Reflectivity before quality control Hydrometeor Reflectivityclassification after quality algorithm control Misclassification rate < 1% when SNR > 10 Hail dB Heavy Rain Big Drops Misclassification rate ~ 5% Moderate Rain when SNR Light Rain AP > 5 dB Birds/Insects Hail Detection • JPOLE hail observations: - 20+ days, 100+ hrs • Two hail chase cars: - 30 Apr-12 Jun 2003 - 5 days, 28 hours • Supplemental data: - Storm Data - Public, media, and spotter reports of hail < 3/4” diameter Improved Hail Detection and Prediction Horizontal reflectivity (ZH) Differential reflectivity (ZDR) This storm was producing 5 1/4 inch diameter hail! Hail Cross correlation coefficient (rHV) Hydrometeor classification alg. More Precise Hail Information Q: Is it hailing at this location? A: NO! WSR-88D Reflectivity Polarimetric Hydrometeor Classification Algorithm Improved Hail Detection and Prediction SCIT-Based HDA POD 0.88 FAR 0.39 CSI 0.56 Polarimetric HCA 0.94 0.08 0.86 Result: Polarimetric radar increased forecasters’ precision, lead time, and confidence in hail forecasts, while decreasing false alarms. 3.5 inch diameter hail at Hawley, Oklahoma 30 April 2003 Photo © 2003 Gary Lillie, Hawley, Oklahoma Volunteer Fire Department Tornado Debris Detection Result: Increased forecaster confidence a damaging tornado was ongoing. Severe weather statements Reflectivity (Z ) Radial Velocity (VR) issued withH enhanced wording. Differential Reflectivity (ZDR) Correlation coefficient (rHV) Wet Microbursts Reflectivity (ZH) Differential Reflectivity (ZDR) Sp. Differential Phase (KDP) Beam Attenuation – Looking down a squall line Reflectivity (ZH) Differential Reflectivity (ZDR) Cross-correlation coefficient (rHV) Beam Attenuation – Normal to a squall line! Reflectivity (ZH) Differential Reflectivity (ZDR) Cross-correlation coefficient (rHV) Flash Flood Warnings & Rainfall Accumulation “Traditional” R(Z) estimate NWS Flash Flood Guidance Polarimetric R(KDP) estimate National Weather Service Arkansas-Red Basin River Forecast Center Tulsa OK ISSUED 0153 PM CDT FRI OCT 18 2002 1HR 3HR 6HR :COUNTY NAME ==== === ==== ==================== 2.4/ 2.7/ 3.3 :ALFALFA 3.0/ 3.6/ 4.5 :ATOKA 2.6/ 3.3/ 4.5 :BECKHAM 2.3/ 2.7/ 3.5 :BLAINE 2.7/ 3.2/ 4.0 :BRYAN Oklahoma mesonet totals and radar rainfall estimates: 14 UTC 18 October 2002 to 14 UTC 20 October 2002 Flash Flood Warnings & Rainfall Accumulation One hour point measurements: Radar estimates vs. gages Flash Flood Warnings & Rainfall Accumulation Bias of radar areal rainfall estimates Spring hail cases Cold season stratiform rain Result: Higher confidence, fewer false alarms for flash flooding during JPOLE ZH at 8.5o – 8 May 2003 2149 UTC KOUN ZDR= ZH - ZV ZDR at 8.5o – 8 May 2003 2149 UTC 4 20,000 ft 3 15,000 ft 8,500 ft 1 9,000 ft 7,000 ft 2 15,000 ft KOUN ZH at 8.5o – 8 May 2003 2149 UTC 4 20,000 ft 3 15,000 ft 8,500 ft 1 9,000 ft 7,000 ft 2 15,000 ft KOUN ZH 16.5o – 8 May 2003 2151 UTC BWER summit 22,000 ft ZDR Winter Weather Warnings Z ZDR 2141 UTC rHV A Z B ZDR 2333 UTC rHV More Lead Time Provided KOUN N T Result: Change in polarimetric radar data prompted 1 forecasts of sleet/snow mixture to be changed to reflect 2 3 more snow and higher4accumulations. Forecaster 6 5 7 and situation awareness enhanced lead time 8 9 increased. OKLAHOMA TEXAS 40 mi 64 km Summary – Polarimetric Radar Enhance Situation Awareness Overwhelm Forecaster MORE DATA!!