national weather association 31 st annual meeting 18 october 2006 cleveland, ohio kevin scharfenberg...

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?

Kevin.Scharfenberg@noaa.gov

Questions?

Kevin.Scharfenberg@noaa.gov

Thank you for listening!Thank you for listening!