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Retrieval and Application of Raindrop Size Distributions From Polarimetric Radar and Disdrometer Data for Retrieval and Application of Raindrop Size Distributions From Polarimetric Radar and Disdrometer Data for Sub-synoptic Scale Systems Petar Bukovčić1, 3, 4, Dušan Zrnić2, 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 73072 4 Atmospheric Radar Research Center (ARRC), University of Oklahoma, Norman Croatian-USA Workshop on Mesometeorology, 19. Jun 2012, Eko park Kraš, Croatia

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

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

Introduction • 2 measurements - 3 parameters • Constraining relation needed • Zhang (2001) Introduction • 2 measurements - 3 parameters • Constraining relation needed • Zhang (2001) proposed μ - Λ relation • μ and Λ highly correlated • 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

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

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

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

Dataset – Data Types • Radar Data • Disdrometer Data • ZH - horizontal Dataset – Data Types • Radar Data • Disdrometer Data • ZH - horizontal reflectivity ZDR - differential reflectivity ρhv - correlation coefficient KOUN • DSDs - dropsize distributions R - rainfall rate D 0 - median volume diameter 2 DVD

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

Methodology – DSD retrievals • • • ZDR and μ-Λ relationship to find two Methodology – DSD retrievals • • • ZDR and μ-Λ relationship to find two parameters ZH to find N 0 Λ, μ and N 0 → N(D) → R, D 0 (DSD parameters)

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

Squall line, May 13, 2005 0730 UTC ZH ZDR ρhv class. KOUN Squall line, May 13, 2005 0730 UTC ZH ZDR ρhv class. KOUN

Squall line, May 13, 2005 N(D) m(D) ZDR(D) 2 DVD Squall line, May 13, 2005 N(D) m(D) ZDR(D) 2 DVD

Squall line, May 13, 2005 ZH ZDR ρhv KOUN – vertical profile over 2 Squall line, May 13, 2005 ZH ZDR ρhv KOUN – vertical profile over 2 DVD location

Squall line, May 13, 2005 ZH R ZDR D 0 Comparison - retrievals, KOUN Squall line, May 13, 2005 ZH R ZDR D 0 Comparison - retrievals, KOUN vs. 2 DVD

Convective-stratiform mix, June 26, 2007 1200 UTC ZH ZDR ρhv class. KOUN Convective-stratiform mix, June 26, 2007 1200 UTC ZH ZDR ρhv class. KOUN

Convective-stratiform mix, June 26, 2007 N(D) m(D) ZDR(D) 2 DVD Convective-stratiform mix, June 26, 2007 N(D) m(D) ZDR(D) 2 DVD

Convective-stratiform mix, June 26, 2007 ZH ZDR ρhv KOUN – vertical profile over 2 Convective-stratiform mix, June 26, 2007 ZH ZDR ρhv KOUN – vertical profile over 2 DVD location

Convective-stratiform mix, June 26, 2007 ZH R ZDR D 0 Comparison - retrievals, KOUN Convective-stratiform mix, June 26, 2007 ZH R ZDR D 0 Comparison - retrievals, KOUN vs. 2 DVD

Convective rain, June 28, 2007 1230 UTC ZH ZDR ρhv class. KOUN Convective rain, June 28, 2007 1230 UTC ZH ZDR ρhv class. KOUN

Convective rain, June 28, 2007 N(D) m(D) ZDR(D) 2 DVD Convective rain, June 28, 2007 N(D) m(D) ZDR(D) 2 DVD

Convective rain, June 28, 2007 ZH ZDR ρhv KOUN – vertical profile over 2 Convective rain, June 28, 2007 ZH ZDR ρhv KOUN – vertical profile over 2 DVD location

Convective rain, June 28, 2007 ZH R ZDR D 0 Comparison - retrievals, KOUN Convective rain, June 28, 2007 ZH R ZDR D 0 Comparison - retrievals, KOUN vs. 2 DVD

Summary and Discussion • Radar data and disdrometer measurements generally agree well for sub-synoptic Summary and Discussion • Radar data and disdrometer measurements generally agree well for sub-synoptic scale systems • Radar retrieved R is in good agreement with 2 DVD and not too 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 2 DVD, but trends match very well • Convective and stratiform stages should be treated separately

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

Thank you! Thank you!

Questions? petar. bukovcic@ou. edu Questions? petar. [email protected] edu