Retrieval and Application of Raindrop Size Distributions From Polarimetric Radar and Disdrometer Data for Sub-synoptic Scale Systems Petar Bukovčić 1,3,4, Dušan Zrnić 2, Guifu Zhang 3,4 1 Cooperative Institute for Mesoscale Meteorological Studies (CIMMS), University of Oklahoma, and NOAA/OAR National Severe Storms Laboratory, Norman, OK 2 National Severe Storms Laboratory (NSSL), University of Oklahoma, Norman 3 School of Meteorology, University of Oklahoma, Norman, OK Atmospheric Radar Research Center (ARRC), University of Oklahoma, Norman Petar Bukovčić 1,3,4, Dušan Zrnić 2, Guifu Zhang 3,4 1 Cooperative Institute for Mesoscale Meteorological Studies (CIMMS), University of Oklahoma, and NOAA/OAR National Severe Storms Laboratory, Norman, OK 2 National Severe Storms Laboratory (NSSL), University of Oklahoma, Norman 3 School of Meteorology, University of Oklahoma, Norman, OK Atmospheric Radar Research Center (ARRC), University of Oklahoma, Norman Croatian-USA Workshop on Mesometeorology, 19. Jun 2012, Eko park Kraš, Croatia

OverviewOverview Introduction Introduction Instrumentation and datasets Instrumentation and datasets Polarimetric KOUN radar Polarimetric KOUN radar 2 Dimensional Video Disdrometers (2DVD) 2 Dimensional Video Disdrometers (2DVD) Dataset Dataset Methodology – DSD retrievals Methodology – DSD retrievals Case studies Case studies Squall line, July 13, 2005 Squall line, July 13, 2005 Convective-stratiform mix, Jun 26, 2007 Convective-stratiform mix, Jun 26, 2007 Convective rain, Jun 28, 2007 Convective rain, Jun 28, 2007 Summary and Discussion Summary and Discussion Introduction Introduction Instrumentation and datasets Instrumentation and datasets Polarimetric KOUN radar Polarimetric KOUN radar 2 Dimensional Video Disdrometers (2DVD) 2 Dimensional Video Disdrometers (2DVD) Dataset Dataset Methodology – DSD retrievals Methodology – DSD retrievals Case studies Case studies Squall line, July 13, 2005 Squall line, July 13, 2005 Convective-stratiform mix, Jun 26, 2007 Convective-stratiform mix, Jun 26, 2007 Convective rain, Jun 28, 2007 Convective rain, Jun 28, 2007 Summary and Discussion Summary and Discussion

Drop Size Distributions (DSDs)- contain essential information about precipitation microphysics Drop Size Distributions (DSDs)- contain essential information about precipitation microphysics Natural DSDs - high variability Natural DSDs - high variability Three parameter model Three parameter model Gamma DSD model: much closer to natural DSDs, more flexible, 3 degrees of freedom (Ulbrich, 1983) Gamma DSD model: much closer to natural DSDs, more flexible, 3 degrees of freedom (Ulbrich, 1983) μ, Λ, N 0 - gamma DSD parameters μ, Λ, N 0 - gamma DSD parameters Z H, Z DR - radar measurements Z H, Z DR - radar measurements Drop Size Distributions (DSDs)- contain essential information about precipitation microphysics Drop Size Distributions (DSDs)- contain essential information about precipitation microphysics Natural DSDs - high variability Natural DSDs - high variability Three parameter model Three parameter model Gamma DSD model: much closer to natural DSDs, more flexible, 3 degrees of freedom (Ulbrich, 1983) Gamma DSD model: much closer to natural DSDs, more flexible, 3 degrees of freedom (Ulbrich, 1983) μ, Λ, N 0 - gamma DSD parameters μ, Λ, N 0 - gamma DSD parameters Z H, Z DR - radar measurements Z H, Z DR - radar measurements IntroductionIntroduction

IntroductionIntroduction 2 measurements - 3 parameters 2 measurements - 3 parameters Constraining relation needed Constraining relation needed Zhang (2001) proposed μ - Λ relation Zhang (2001) proposed μ - Λ relation μ and Λ highly correlated μ and Λ highly correlated D 0 and the shape of a rain drop spectrum are related → physical meaning of μ – Λ D 0 and the shape of a rain drop spectrum are related → physical meaning of μ – Λ Cao (2008) → unified μ –Λ relation for Oklahoma used for both convective and stratiform DSD retrievals Cao (2008) → unified μ –Λ relation for Oklahoma used for both convective and stratiform DSD retrievals 2 measurements - 3 parameters 2 measurements - 3 parameters Constraining relation needed Constraining relation needed Zhang (2001) proposed μ - Λ relation Zhang (2001) proposed μ - Λ relation μ and Λ highly correlated μ and Λ highly correlated D 0 and the shape of a rain drop spectrum are related → physical meaning of μ – Λ D 0 and the shape of a rain drop spectrum are related → physical meaning of μ – Λ Cao (2008) → unified μ –Λ relation for Oklahoma used for both convective and stratiform DSD retrievals Cao (2008) → unified μ –Λ relation for Oklahoma used for both convective and stratiform DSD retrievals

Instrumentation - KOUN Polarimetric Radar: KOUN – Norman, OK Polarimetric Radar: KOUN – Norman, OK Provides info about hydrometeor size, shape, phase, and orientation Provides info about hydrometeor size, shape, phase, and orientation Allow retrieval of drop size distributions (DSDs) Allow retrieval of drop size distributions (DSDs) Polarimetric Radar: KOUN – Norman, OK Polarimetric Radar: KOUN – Norman, OK Provides info about hydrometeor size, shape, phase, and orientation Provides info about hydrometeor size, shape, phase, and orientation Allow retrieval of drop size distributions (DSDs) Allow retrieval of drop size distributions (DSDs)

Instrumentation – 2DVD Joanneum Research 2D Video Disdrometer Joanneum Research 2D Video Disdrometer low profile, OU low profile, OU OU KFFL (Kessler’s Farm Field Laboratory) OU KFFL (Kessler’s Farm Field Laboratory) Joanneum Research 2D Video Disdrometer Joanneum Research 2D Video Disdrometer low profile, OU low profile, OU OU KFFL (Kessler’s Farm Field Laboratory) OU KFFL (Kessler’s Farm Field Laboratory) OU 2DVD

Instrumentation – 2DVD Joanneum Research 2D Video Disdrometer Joanneum Research 2D Video Disdrometer low profile, OU low profile, OU OU KFFL (Kessler’s Farm Field Laboratory) OU KFFL (Kessler’s Farm Field Laboratory) 2DVD directly measures the shape, size and falling velocity of precipitation particles 2DVD directly measures the shape, size and falling velocity of precipitation particles OU 2DVD

Dataset – Data Types KOUNKOUN 2DVD2DVD Disdrometer Data Disdrometer Data DSDs - dropsize distributions R - rainfall rate D 0 - median volume diameter DSDs - dropsize distributions R - rainfall rate D 0 - median volume diameter Disdrometer Data Disdrometer Data DSDs - dropsize distributions R - rainfall rate D 0 - median volume diameter DSDs - dropsize distributions R - rainfall rate D 0 - median volume diameter Radar Data Radar Data Z H - horizontal reflectivity Z DR - differential reflectivity ρ hv - correlation coefficient Z H - horizontal reflectivity Z DR - differential reflectivity ρ hv - correlation coefficient Radar Data Radar Data Z H - horizontal reflectivity Z DR - differential reflectivity ρ hv - correlation coefficient Z H - horizontal reflectivity Z DR - differential reflectivity ρ hv - correlation coefficient

Gamma DSD Gamma DSD N(D) - DSDN(D) - DSD N 0 (mm -1- μ m -3 ) - number concentration parameterN 0 (mm -1- μ m -3 ) - number concentration parameter μ - the shape distribution parameter μ - the shape distribution parameter Λ (mm -1 ) - the slope parameterΛ (mm -1 ) - the slope parameter D ( mm ) - the equivalent volume diameterD ( mm ) - the equivalent volume diameter Constraining relation for OK rain (Cao et al. 2008) Constraining relation for OK rain (Cao et al. 2008) Methodology – DSD retrievals

Z DR and μ-Λ relationship to find two parameters Z DR and μ-Λ relationship to find two parameters Z H to find N 0 Z H to find N 0 Λ, μ and N 0 → N(D) → R, D 0 (DSD parameters) Λ, μ and N 0 → N(D) → R, D 0 (DSD parameters) Methodology – DSD retrievals

Case Studies Several types of storms: Several types of storms: > Squall line, July 13, 2007; > Squall line, July 13, 2007; > Convective-stratiform mix, June 26, 2007; > Convective-stratiform mix, June 26, 2007; > Convective rain, June 28, 2007; > Convective rain, June 28, 2007; Several types of storms: Several types of storms: > Squall line, July 13, 2007; > Squall line, July 13, 2007; > Convective-stratiform mix, June 26, 2007; > Convective-stratiform mix, June 26, 2007; > Convective rain, June 28, 2007; > Convective rain, June 28, 2007;

Squall line, May 13, UTC Z DR ZHZHZHZH ZHZHZHZH ρ hv class.class. KOUNKOUN

Squall line, May 13, 2005 N(D)N(D) m(D)m(D) Z(D)Z(D) Z DR (D) 2DVD2DVD

Squall line, May 13, 2005 ZHZHZHZH ZHZHZHZH Z DR ρ hv KOUN – vertical profile over 2DVD location

Squall line, May 13, 2005 Comparison - retrievals, KOUN vs. 2DVD RR D0D0D0D0 D0D0D0D0 ZHZHZHZH ZHZHZHZH Z DR

1200 UTC Z DR ZHZHZHZH ZHZHZHZH ρ hv class.class. KOUNKOUN Convective-stratiform mix, June 26, 2007

2DVD2DVD N(D)N(D) m(D)m(D) Z(D)Z(D) Z DR (D) Convective-stratiform mix, June 26, 2007

ZHZHZHZH ZHZHZHZH Z DR ρ hv KOUN – vertical profile over 2DVD location Convective-stratiform mix, June 26, 2007

ZHZHZHZH ZHZHZHZH RR D0D0D0D0 D0D0D0D0 Z DR Comparison - retrievals, KOUN vs. 2DVD

Convective rain, June 28, UTC Z DR ZHZHZHZH ZHZHZHZH ρ hv class.class. KOUNKOUN

Convective rain, June 28, 2007 N(D)N(D) m(D)m(D) Z(D)Z(D) Z DR (D) 2DVD2DVD

Convective rain, June 28, 2007 ZHZHZHZH ZHZHZHZH Z DR ρ hv KOUN – vertical profile over 2DVD location

Convective rain, June 28, 2007 ZHZHZHZH ZHZHZHZH RR D0D0D0D0 D0D0D0D0 Z DR Comparison - retrievals, KOUN vs. 2DVD

Radar data and disdrometer measurements generally agree well for sub-synoptic scale systems Radar data and disdrometer measurements generally agree well for sub-synoptic scale systems Radar retrieved R is in good agreement with 2DVD and not too sensitive if μ –Λ changes Radar retrieved R is in good agreement with 2DVD and not too sensitive if μ –Λ changes D 0 → highly sensitive if μ –Λ changes D 0 → highly sensitive if μ –Λ changes Radar retrieved D 0 → slightly lower in stratiform and higher in convective stages of the storm compared to 2DVD, but trends match very well Radar retrieved D 0 → slightly lower in stratiform and higher in convective stages of the storm compared to 2DVD, but trends match very well Convective and stratiform storm stages should be treated separately Radar data and disdrometer measurements generally agree well for sub-synoptic scale systems Radar data and disdrometer measurements generally agree well for sub-synoptic scale systems Radar retrieved R is in good agreement with 2DVD and not too sensitive if μ –Λ changes Radar retrieved R is in good agreement with 2DVD and not too sensitive if μ –Λ changes D 0 → highly sensitive if μ –Λ changes D 0 → highly sensitive if μ –Λ changes Radar retrieved D 0 → slightly lower in stratiform and higher in convective stages of the storm compared to 2DVD, but trends match very well Radar retrieved D 0 → slightly lower in stratiform and higher in convective stages of the storm compared to 2DVD, but trends match very well Convective and stratiform storm stages should be treated separately Summary and Discussion

Reliable DSD retrieval technique is essential for accurate rain estimation and model parameterization Reliable DSD retrieval technique is essential for accurate rain estimation and model parameterization Future work Future work Implementation of polarimetric radar data into NWP models Implementation of polarimetric radar data into NWP models Link between dynamics and microphysics (dual Doppler analysis) Link between dynamics and microphysics (dual Doppler analysis) μ - Λ adjustment (big drops, long tail DSDs)μ - Λ adjustment (big drops, long tail DSDs) Separation of convective and stratiform stages Separation of convective and stratiform stages Reliable DSD retrieval technique is essential for accurate rain estimation and model parameterization Reliable DSD retrieval technique is essential for accurate rain estimation and model parameterization Future work Future work Implementation of polarimetric radar data into NWP models Implementation of polarimetric radar data into NWP models Link between dynamics and microphysics (dual Doppler analysis) Link between dynamics and microphysics (dual Doppler analysis) μ - Λ adjustment (big drops, long tail DSDs)μ - Λ adjustment (big drops, long tail DSDs) Separation of convective and stratiform stages Separation of convective and stratiform stages

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