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

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 ……  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 ……

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?  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?

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  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 Particle images, electric field, IWC, LWC,w, Z h,Z dr, LDR, A 3 CP-2,CP-3,Cp-4 P-3, T28, WKA, NKA

Evolution of The Strom Time:1758: cell B vigorous growth Z h ~40dBZ, w~14m/s Z dr column up to 6.5km Time:1803:A number of new cells formed Time:1808:Strongest updraft in cell A (16m/s) Z dr column up to 6.0 km with values exceeding 3dB from 2-5km Time:1810:Cell A in vigorous growth P-3 penetrates cell a along X” from SE to NW, at Time:1814:A new updraft core,cell A’, developed to the SE of cell A. Time:1821:Cell A remains dominant, but Z dr column down to 4-km, with maximum value down to 2dB 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

Vigorous Growth Period--Cell A

Cell A: radar evolution First updraft pulse Enhanced LDR cap 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 IWC grows between 5-7km Max rain flux at 2-km level 600s after first updraft

Cell A: Snapshot at 1810 UTC SE NW

Cell A: Mixed phase domain Radar signals Z h contour Z dr gray scale Z dr contour LDR r gray scale Z dr contour A 3 gray scale Z h >40dB Z dr >1dB LDR>-21dB A3~ dB Microphysics Mixed phase domain Super cooled drop, frozen and partially frozen drops

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

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.

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

Cell D: Snapshot at1808UTC Relative Low Z h ~35dBZ, High Z dr ~2.5dB Warm rain process: Large drops Low concentration Active coalescence process

Cell D VS Cell A Cell A: W~12m/s Z h ~45-50dBZ Z dr ~1.5dB LDR~-21dB Cell D: W~12m/s Z h ~30-35dBZ Z dr ~2.5dB LDR N/A

Penetration height: 6.5km Temperature :-11 o C Max w height: 6.0km IWC~1.5g/m 3 LWC<0.5g/m 3 Penetration height: 5.5/4.0 km Temperature :-6 o C/3 o C Max w height: 5.0km IWC 0.4g/m 3

Mature structure at 1827UTC Cell A’ SE NW A” A’

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

Conclusions & Summary By Authors  A typical thunderstorm in CaPE study  Typical radar structure in all developing cell: Z dr column exceeding above freezing level, with LDR “cap” above the maximum altitude that Z dr can reach.  High Z dr low Z h region associated with low concentration of millimeter-size drops; enhanced LDR(A 3 ) region indicates mixed phase condition  Highest cloud water concentration in updrafts accompanied by low concentration of large drops   A typical thunderstorm in CaPE study  Typical radar structure in all developing cell: Z dr column exceeding above freezing level, with LDR “cap” above the maximum altitude that Z dr can reach.  High Z dr low Z h region associated with low concentration of millimeter-size drops; enhanced LDR(A 3 ) region indicates mixed phase condition  Highest cloud water concentration in updrafts accompanied by low concentration of large drops 

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 Z dr low Z h region associated with low concentration of large drops  More work could be done…  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 Z dr low Z h region associated with low concentration of large drops  More work could be done…

Thank You