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Petar Bukov čić 1,3,4 , Du šan Zrnić 2 , Guifu Zhang 3,4

Retrieval and Application of Raindrop Size Distributions From Polarimetric Radar and Disdrometer Data for Sub-synoptic Scale Systems. Petar Bukov čić 1,3,4 , Du šan Zrnić 2 , Guifu Zhang 3,4

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Petar Bukov čić 1,3,4 , Du šan Zrnić 2 , Guifu Zhang 3,4

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  1. 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 Zhang3,4 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

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

  3. 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, N0 - gamma DSD parameters • ZH,ZDR - radar measurements

  4. Introduction • 2 measurements - 3 parameters • Constraining relation needed • Zhang (2001) proposed μ - Λ relation • μandΛhighly correlated • D0 and the shape of a rain drop spectrum are related → physical meaning of μ – Λ • Cao (2008) → unified μ –Λrelation for Oklahoma usedfor both convective and stratiform DSD retrievals

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

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

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

  8. Dataset – Data Types • Radar Data • ZH - horizontal reflectivity ZDR - differential reflectivity ρhv - correlation coefficient • Disdrometer Data • DSDs - dropsize distributions R - rainfallrate D0 - median volume diameter 2DVD KOUN

  9. Gamma DSD N(D) - DSD N0(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

  10. ZDR and μ-Λ relationship to find two parameters ZH to find N0 Λ,μandN0→ N(D) → R,D0 (DSD parameters) Methodology – DSD retrievals

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

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

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

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

  15. Squall line, May 13, 2005 ZH R ZDR D0 Comparison - retrievals, KOUN vs. 2DVD

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

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

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

  19. Convective-stratiform mix, June 26, 2007 ZH R ZDR D0 Comparison - retrievals, KOUN vs. 2DVD

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

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

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

  23. Convective rain, June 28, 2007 ZH R ZDR D0 Comparison - retrievals, KOUN vs. 2DVD

  24. Summary and Discussion • 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 • D0 → highly sensitive ifμ –Λchanges • Radar retrieved D0→ 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

  25. 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 - Λadjustment (big drops, long tail DSDs) • Separation of convective and stratiform stages

  26. Thank you!

  27. Questions? petar.bukovcic@ou.edu

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