national weather association 31 st annual meeting 18 october 2006 cleveland, ohio kevin scharfenberg...
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National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Kevin ScharfenbergUniversity of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies
and NOAA/National Severe Storms Laboratory, Norman, OK
Kevin ScharfenbergUniversity of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies
and NOAA/National Severe Storms Laboratory, Norman, OK
Dual-pol Radar in Operational Forecasting:an overview
Dual-pol Radar in Operational Forecasting:an overview
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Dual-pol Review
• Fewer flash flood warning false alarms
• Reliable hail detection
• High resolution precip typing
in winter storms
• Much cleaner data displays
• Fewer flash flood warning false alarms
• Reliable hail detection
• High resolution precip typing
in winter storms
• Much cleaner data displays
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Dual-pol Review
• Pre-processor algorithm
• Hydrometeor classification algorithm
• Rain accumulation algorithms– Biggest improvements in
heavy rain, near radar
• Pre-processor algorithm
• Hydrometeor classification algorithm
• Rain accumulation algorithms– Biggest improvements in
heavy rain, near radar
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Precip. Estimation
Just as there areempirical relationshipsbetween rainfall rate &(horizontal) reflectivity…
Just as there areempirical relationshipsbetween rainfall rate &(horizontal) reflectivity…
R(Zh)
R = (0.171 Zh)0.714
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Precip. Estimation
Just as there areempirical relationshipsbetween rainfall rateand reflectivity…
…there are alsoempirical relationshipsbetween rainfall rateand dual-pol variables
R(KDP)R(Zh)
R = (0.171 Zh)0.714 R = 44 |KDP|0.822 sign(KDP)
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Rainfall Estimation
Dual-pol rainfall estimators provide the most improvement in heavy rain (hail?)– Use R(KDP) in heavy rain
– Use R(KDP, ZDR) in moderate rain
– Use R(Zh, ZDR) in light rain
We call it the “synthetic” dual-pol QPE algorithm
Dual-pol rainfall estimators provide the most improvement in heavy rain (hail?)– Use R(KDP) in heavy rain
– Use R(KDP, ZDR) in moderate rain
– Use R(Zh, ZDR) in light rain
We call it the “synthetic” dual-pol QPE algorithm
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Rainfall Estimation
Dual-pol rainfall estimators provide the most improvement near the radar– Use R(synthetic) within 120 km
– Use R(KDP) from 120-200 km range
– Use R(Zh) beyond 200 km
We call it the “combined” dual-pol QPE algorithm
Dual-pol rainfall estimators provide the most improvement near the radar– Use R(synthetic) within 120 km
– Use R(KDP) from 120-200 km range
– Use R(Zh) beyond 200 km
We call it the “combined” dual-pol QPE algorithm
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Case Study
• 14 May 2003 – very early morning
• “Training” high-precip. supercell storms
• Flash flood guidance:– 2.6 inches in 1 hours– 3.0 inches in 3 hours– 3.8 inches in 6 hours
• 14 May 2003 – very early morning
• “Training” high-precip. supercell storms
• Flash flood guidance:– 2.6 inches in 1 hours– 3.0 inches in 3 hours– 3.8 inches in 6 hours
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Case Study
Potential flash flood warning?Potential flash flood warning?
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Case Study
Potential flash flood warning?Potential flash flood warning?
R(Zh) Z=300R1.4R(Zh) Z=300R1.4
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Case Study
Potential flash flood warning?
Dual-pol combined
Potential flash flood warning?Potential flash flood warning?
Dual-pol combinedDual-pol combined
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Case Study
Decision: No flashflood warning issued
Result: No significantflash floodingwas reported
Decision: No flashflood warning issued
Result: No significantflash floodingwas reported
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Conclusions
• Major improvement in this case due to hail contamination in R(Z) product
• Dual-pol also helps with:– Bright-band contamination– Attenuation and partial beam blockage– Filtering out non-precipitation echoes
• Most of the improvement is near the radar – All algorithms perform poorly beyond 200 km
• Major improvement in this case due to hail contamination in R(Z) product
• Dual-pol also helps with:– Bright-band contamination– Attenuation and partial beam blockage– Filtering out non-precipitation echoes
• Most of the improvement is near the radar – All algorithms perform poorly beyond 200 km
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Discussion
• Dual-pol algorithms are still in their infancy
• 100s of potential rainfall algorithms– Multiple radar 3D merger of base data– Add in more hydrometeor classification info.– Integrate with other data sources and run
precip. estimation ensembles!
• Little work so far on snow accumulation estimation!
• Dual-pol algorithms are still in their infancy
• 100s of potential rainfall algorithms– Multiple radar 3D merger of base data– Add in more hydrometeor classification info.– Integrate with other data sources and run
precip. estimation ensembles!
• Little work so far on snow accumulation estimation!
National Weather Association 31st Annual Meeting18 October 2006 Cleveland, Ohio
Questions?
Questions?
Thank you for listening!Thank you for listening!