Future QPE: Dual-Pol and Gap-Filler Radars
Post on 31-Dec-2015
31 Views
Preview:
DESCRIPTION
Transcript
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Future QPE: Dual-Pol and Gap-Filler Radars
Future QPE: Dual-Pol and Gap-Filler Radars
Kevin Scharfenberg
University of Oklahoma/CIMMS and
NOAA National Severe Storms Laboratory
Kevin Scharfenberg
University of Oklahoma/CIMMS and
NOAA National Severe Storms Laboratory
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
WSR-88D RAINFALL RATE COMPARISON [in/hr]
Z [dBZ]Marshall-Palmer
Z=200R1.6
East-Cool Stratiform
Z=130R2.0
West-Cool Stratiform
Z=75R2.0
88D Convective
Z=300R1.4
Rosenfeld Tropical
Z=250R1.2
15 0.01 in/hr 0.02 in/hr 0.03 in/hr <0.01 in/hr <0.01 in/hr
20 0.03 in/hr 0.04 in/hr 0.05 in/hr 0.02 in/hr 0.02 in/hr
25 0.05 in/hr 0.06 in/hr 0.08 in/hr 0.04 in/hr 0.05 in/hr
30 0.11 in/hr 0.11 in/hr 0.14 in/hr 0.09 in/hr 0.13 in/hr
35 0.22 in/hr 0.19 in/hr 0.26 in/hr 0.21 in/hr 0.33 in/hr
40 0.45 in/hr 0.35 in/hr 0.46 in/hr 0.48 in/hr 0.85 in/hr
45 0.93 in/hr 0.61 in/hr 0.81 in/hr 1.10 in/hr 2.22 in/hr
50 1.91 in/hr 1.09 in/hr 1.44 in/hr 2.50 in/hr 5.80 in/hr
55 3.93 in/hr 1.94 in/hr 2.56 in/hr 5.68 in/hr 15.14 in/hr
60 8.07 in/hr 3.45 in/hr 4.55 in/hr 12.93 in/hr 39.53 in/hr
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Dual-polarization in one slide
Dual-polarization in one slide
• Current state: linear horizontal E pulses: — — — … • Original WSR-88D contract specified capability for
later upgrade to dual-pol • After upgrade, WSR-88D will transmit simultaneous
horizontal/vertical pulse (“slant 45º”): ∕ ∕ ∕ ∕ …• Separate receivers will listen for horizontal and
vertical backscatter
• Current state: linear horizontal E pulses: — — — … • Original WSR-88D contract specified capability for
later upgrade to dual-pol • After upgrade, WSR-88D will transmit simultaneous
horizontal/vertical pulse (“slant 45º”): ∕ ∕ ∕ ∕ …• Separate receivers will listen for horizontal and
vertical backscatter
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Early dual-pol QPE resultsEarly dual-pol QPE results
Point Estimates
Areal (basin) Estimates
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Spring hail cases
Cold season stratiform rain
Bias of radar areal rainfall estimates
Early dual-pol QPE resultsEarly dual-pol QPE results
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Reflectivity (Zh)Differential reflectivity (Zdr)
Similar reflectivity – very different differential reflectivity!Northeast – Mostly large rain dropsSouthwest – Mostly hail
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Reflectivity (Zh)Differential reflectivity (Zdr)
Similar reflectivity – very different differential reflectivity!Northwest – relatively large number of relatively small dropsSoutheast – relatively small number of relatively large drops
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
Warm raincase – A very unusual DSD!
Warm raincase – A very unusual DSD!
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
Hail case –Z-R relationsbreak down!
Hail case –Z-R relationsbreak down!
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Z ZDR
KDPhv
RHI instratiformrainfall
RHI instratiformrainfall
Hydrometeor ClassificationHydrometeor Classification
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Hydrometeor classification algorithm
No EchoLgt/mod
rainHeavy
rainHail
“Big drops”
GraupelIce
crystalsDry
snowWet
snowUnknown
AP orClutter
Biological
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Operational strategy
Where HCA detects Use R=Ground clutter / AP / biologicals 0Rain R(Z, Zdr)Possible hail below melting layer R(KDP)Wet snow 0.6R(Z)Graupel/hail above melting layer 0.8R(Z)Dry snow / ice crystals 2.8R(Z)
R(Z) is from standard WSR-88D R(Z) equations.
Operational strategy
Where HCA detects Use R=Ground clutter / AP / biologicals 0Rain R(Z, Zdr)Possible hail below melting layer R(KDP)Wet snow 0.6R(Z)Graupel/hail above melting layer 0.8R(Z)Dry snow / ice crystals 2.8R(Z)
R(Z) is from standard WSR-88D R(Z) equations.
Dual-pol QPE AlgorithmDual-pol QPE Algorithm
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
NCAR SPOL radar ; From Vivekanandan et al. 1999, JTech 16, 837-845
Dual-pol and partial attenuationDual-pol and partial attenuation
Partial terrain blockagePartial terrain blockage
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
WSR-88D coverage at 3 km AGLWSR-88D coverage at 3 km AGL
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
“Gap-Filler” Boundary Layer Radars
“Gap-Filler” Boundary Layer Radars
CourtesyCASA projectCourtesyCASA project
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
“Gap-Filler” Boundary Layer Radars
“Gap-Filler” Boundary Layer Radars
Nearest WSR-88D CASA radars
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
- Dual-pol WSR-88D upgrade - Dual-pol, low-power “gap-filler” radars
- Multiple-radar data mergers incorporating NWP
- Corrections for dual-pol radar QPE using rain gages
- Incorporation of dual-pol base data vertical profiles
- Incorporate corrections for partial beam attenuation (including partial terrain blockage!)
- Dual-pol WSR-88D upgrade - Dual-pol, low-power “gap-filler” radars
- Multiple-radar data mergers incorporating NWP
- Corrections for dual-pol radar QPE using rain gages
- Incorporation of dual-pol base data vertical profiles
- Incorporate corrections for partial beam attenuation (including partial terrain blockage!)
Radar-based QPE: The FutureRadar-based QPE: The Future
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Questions?Questions?
Kevin.Scharfenberg@noaa.govKevin.Scharfenberg@noaa.gov
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
R(Z) on a 2 km x 2 km gridR(Z) on a 2 km x 2 km grid
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
Dual-pol QPE on a 2 km x 2 km gridDual-pol QPE on a 2 km x 2 km grid
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Increasing value
Hei
ght * * *
Hydrometeor ClassificationHydrometeor Classification
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Operational QPE algorithm
- Significant improvement over R(Z), particularly inside 150 km and in heavy rain (and possible hail)
- Measurable improvement 150-230 km
- Measurable improvement over adjusted R(Z) using vertical Zh profiles/mean-field bias (MFB) corrections
- Later work to incorporate multiple radars, corrections using MFB, vertical dual-pol profiles, beam attenuation
Operational QPE algorithm
- Significant improvement over R(Z), particularly inside 150 km and in heavy rain (and possible hail)
- Measurable improvement 150-230 km
- Measurable improvement over adjusted R(Z) using vertical Zh profiles/mean-field bias (MFB) corrections
- Later work to incorporate multiple radars, corrections using MFB, vertical dual-pol profiles, beam attenuation
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Differential Reflectivity (Zdr)
Differential Reflectivity (Zdr)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
• Indicates the presence of larger liquid drops• Indicates the presence of larger liquid drops
• Hail shafts without a lot of liquid water
Differential Reflectivity (Zdr)
Differential Reflectivity (Zdr)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Differential reflectivityZdr = 10 log (Eh/Ev)
= Zh - Zv [dB]
The reflectivity-weighted mean axis ratio of scatterers in a sample volume
Zdr > 0 Horizontally-oriented mean profile
Zdr < 0 Vertically-oriented mean profile
Zdr ~ 0 Near-spherical mean profile
Differential reflectivityZdr = 10 log (Eh/Ev)
= Zh - Zv [dB]
The reflectivity-weighted mean axis ratio of scatterers in a sample volume
Zdr > 0 Horizontally-oriented mean profile
Zdr < 0 Vertically-oriented mean profile
Zdr ~ 0 Near-spherical mean profile
Eh
Ev
Differential Reflectivity (Zdr)
Differential Reflectivity (Zdr)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Differential Phase Shift DP = h – v (h, v ≥ 0) [deg]
The difference in phase between the horizontally-and vertically-polarized pulses at a given range along the propagation path.
- Two-way process- Independent of partial beam blockage, attenuation- Independent of absolute radar calibration- Immune to propagation effects on calibration- Independent of system noise
Differential Phase Shift DP = h – v (h, v ≥ 0) [deg]
The difference in phase between the horizontally-and vertically-polarized pulses at a given range along the propagation path.
- Two-way process- Independent of partial beam blockage, attenuation- Independent of absolute radar calibration- Immune to propagation effects on calibration- Independent of system noise
Differential Phase Shift (DP)
Differential Phase Shift (DP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Specific Differential Phase Shift DP(r2) – DP(r1)
KDP = [deg/km] 2 (r2 – r1)
The range derivative of differential phase shift
- Identify areas with significantly non-spherical scatterers (usually, rain)- Can estimate rain amount in rain/hail mixture
Specific Differential Phase Shift DP(r2) – DP(r1)
KDP = [deg/km] 2 (r2 – r1)
The range derivative of differential phase shift
- Identify areas with significantly non-spherical scatterers (usually, rain)- Can estimate rain amount in rain/hail mixture
Specific Differential Phase Shift (KDP)
Specific Differential Phase Shift (KDP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Specific Differential Phase Shift (KDP)
Specific Differential Phase Shift (KDP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Result: The KDP dilemma
- Using a long-distance derivative for calculating KDP can oversmooth heavy rain features but reduces noise
- Using a short-distance derivative for calculating KDP retains features in heavy rain but is also noisy
Result: The KDP dilemma
- Using a long-distance derivative for calculating KDP can oversmooth heavy rain features but reduces noise
- Using a short-distance derivative for calculating KDP retains features in heavy rain but is also noisy
Specific Differential Phase Shift (KDP)
Specific Differential Phase Shift (KDP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Calculating KDP: current practice
- If Z > 40 dBZ, use a KDP calculation range of 9 gates (2 km).
- Otherwise, use a range derivative of 25 gates (6 km)
- Filter the final KDP product at 0.9 hv
Calculating KDP: current practice
- If Z > 40 dBZ, use a KDP calculation range of 9 gates (2 km).
- Otherwise, use a range derivative of 25 gates (6 km)
- Filter the final KDP product at 0.9 hv
Specific Differential Phase Shift (KDP)
Specific Differential Phase Shift (KDP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
OutlineOutlineDifferential phase shift (DP)
Differential phase shift (DP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
OutlineOutlineSpecific differential phase shift (KDP)
Specific differential phase shift (KDP)
21 September 2007 4th Southwest Hydrometeorology Symposium, Tucson, AZ
Rainfall estimation using polarimetric variables
R(Z, ZDR) = 0.0142 Z0.77 ZDR-1.67
[mm/h]
R(KDP) = 44|KDP|0.822 sign(KDP) [mm/h]
Rainfall estimation using polarimetric variables
R(Z, ZDR) = 0.0142 Z0.77 ZDR-1.67
[mm/h]
R(KDP) = 44|KDP|0.822 sign(KDP) [mm/h]
Quantitative Precipitation Estimation
Quantitative Precipitation Estimation
top related