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Paper Review By Zhibo Zhang

Evolution of a Florida Thunderstorm during the Convection and Precipitation/Electrification Experiment: The Case of 9 August 1991. Paper Review By Zhibo Zhang. Paper Overview. Motivation

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Paper Review By Zhibo Zhang

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  1. Evolution of a Florida Thunderstorm during the Convection and Precipitation/Electrification Experiment: The Case of 9 August 1991 Paper Review By Zhibo Zhang

  2. Paper Overview • Motivation Presents an analytical, detailed and vivid description of the evolution of a multicell thunderstorm , with particular focus on the relationships among kinematic, microphysical and electric field. • Event A multicell thunderstorm,9 August 1991, in Florida • Characteristics Various observation platforms involved Good overlapping coverage in radar and aircraft data (three Doppler radars, four aircrafts, a surface electric field net work, etc…) • Main Results ……

  3. Our Questions • Motivation Did the authors success to give the us a clear and convincing analysis about the relationships between kinematic, microphysical and electric field properties? • Event What’s going on in that storm according to the authors and why did they think so? • Characteristics How did the data coming from different facilities work together? Is this more supportive or causing more troubles? • Main Results Which one is most exciting? Which one may not be common in other cases?

  4. Background Knowledge • CaPE project(Convective and Precipitation/Electrification, East Central Florida, 8 July -18 August, 1991) Objective: Identify the relationships among the coevolving wind, water, and electric fields within convective clouds. • Observation facilities CP-2,CP-3,Cp-4 P-3, T28, WKA, NKA Particle images, electric field, IWC, LWC,w, Zh,Zdr, LDR, A3

  5. Evolution of The Strom Time:1827:Cell A’ in mature stage, with a young developing cell, A”, at SE. T-28 penetrates cell A’ and A” along X”’, from SE to NW, at 182645-182845 Time:1758: cell B vigorous growth Zh~40dBZ, w~14m/s Zdr column up to 6.5km Time:1803:A number of new cells formed Time:1810:Cell A in vigorous growth P-3 penetrates cell a along X” from SE to NW, at 180937-181027 Time:1808:Strongest updraft in cell A (16m/s) Zdr column up to 6.0 km with values exceeding 3dB from 2-5km Time:1814:A new updraft core,cell A’, developed to the SE of cell A. Time:1821:Cell A remains dominant, but Zdr column down to 4-km, with maximum value down to 2dB

  6. Vigorous Growth Period--Cell A

  7. IWC grows between 5-7km Enhanced LDR cap Max rain flux at 2-km level 600s after first updraft First updraft pulse Cell A: radar evolution • First updraft around 1810(360s) carries raindrops to low temperature and they freeze • LDR cap • IWC grows between 5-7km at beginning, leads to max rain flux 600s later at 2-km level

  8. Cell A: Snapshot at 1810 UTC 181027 180937 SE NW

  9. Cell A: Mixed phase domain Zh contour Zdr gray scale Zdr contour A3 gray scale Zdr contour LDRr gray scale Zh>40dB Zdr>1dB LDR>-21dB A3~0.5-1.5dB Radar signals Mixed phase domain Super cooled drop, frozen and partially frozen drops Microphysics

  10. Cell A: Particle images Smooth edge+elliptical cross section ~liquid drops (distortion of airflow) Circular cross section ~Frozen drops (unlikely to be distorted)) Particle image suggests The mixed phase domain

  11. Cell A: Theoretical calculation • Size distribution model (in situ observation) • Particle model: super-cooled oblate water drops with • concentric oblate ice shell • Orientation(distortion angles): Gaussian distribution Proper set up of size distribution, Particle and distortion model can give rise to measured radar signals, without invoking wet growth.

  12. Cell D: Radar evolution & Aircraft penetration 1,WKA 4km,1804 2a,WKA,5.5km 1808 2b,NKA,4.5km 1808 3a,WKA,5.5km 1811 3b,NKA,4.0km 1811

  13. Cell D: Snapshot at1808UTC Relative Low Zh~35dBZ, High Zdr~2.5dB Warm rain process: Large drops Low concentration Active coalescence process

  14. Cell D VS Cell A Cell A: W~12m/s Zh~45-50dBZ Zdr~1.5dB LDR~-21dB Cell D: W~12m/s Zh~30-35dBZ Zdr~2.5dB LDR N/A

  15. Penetration height: 6.5km Temperature :-11oC Max w height: 6.0km IWC~1.5g/m3 LWC<0.5g/m3 Penetration height: 5.5/4.0 km Temperature :-6oC/3oC Max w height: 5.0km IWC<0.4g/m3 LWC>0.4g/m3

  16. Mature structure at 1827UTC Cell A’ A’ A” 1828.45 1826.45 NW SE

  17. Cell A’:Particle images Center of A” Young developing cell Liquid drops Center of A’ Mature cell Rough-edged graupel

  18. Conclusions & Summary By Authors • A typical thunderstorm in CaPE study • Typical radar structure in all developing cell: Zdr column exceeding above freezing level, with LDR “cap” above the maximum altitude that Zdr can reach. • High Zdr low Zh region associated with low concentration of millimeter-size drops; enhanced LDR(A3) region indicates mixed phase condition • Highest cloud water concentration in updrafts accompanied by low concentration of large drops

  19. Comments?! • Most valuable thing--in situ observation, quantitative data, especially the co-overlapping region covered by both radar and aircraft • Excellent description of the structure and development of each cell in this thunderstorm • Good analysis about the mixed phase domain in cell A • In situ observation of the high Zdr low Zh region associated with low concentration of large drops • More work could be done…

  20. Thank You

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