Evolution of a Florida Thunderstorm during the Convection and

Precipitation/Electrification Experiment:

The Case of 9 August 1991

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 OverviewPaper 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 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 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,Zh,Zdr, LDR, A3

CP-2,CP-3,Cp-4 P-3, T28, WKA, NKA

Evolution of The Strom Evolution of The Strom

Time:1758: cell B vigorous growth Zh~40dBZ, w~14m/s Zdr column up to 6.5km

Time:1803:A number of new cells formedTime:1808:Strongest updraft in cell A (16m/s) Zdr 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 180937-181027

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

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

Vigorous Growth Period--Cell AVigorous Growth Period--Cell A

Cell A: radar evolution 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 UTCCell A: Snapshot at 1810 UTC

180937181027

SENW

Cell A: Mixed phase domainCell A: Mixed phase domain

Radar signals

Zh contour Zdr gray scaleZdr contour LDRr gray scale Zdr contour A3 gray scale

Zh>40dB Zdr>1dB LDR>-21dB A3~0.5-1.5dB

Microphysics Mixed phase domainSuper cooled drop, frozen and partially frozen drops

Cell A: Particle imagesCell 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 calculationCell 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 Cell D: Radar evolution & Aircraft

penetration 1,WKA 4km,1804

2a,WKA,5.5km 18082b,NKA,4.5km 1808

3a,WKA,5.5km 18113b,NKA,4.0km 1811

Cell D: Snapshot at1808UTC Cell D: Snapshot at1808UTC

Relative Low Zh~35dBZ,High Zdr~2.5dB

Warm rain process: Large drops Low concentrationActive coalescence process

Cell D VS Cell A 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

Penetration height: 6.5kmTemperature :-11oCMax w height: 6.0kmIWC~1.5g/m3 LWC<0.5g/m3

Penetration height: 5.5/4.0 kmTemperature :-6oC/3oCMax w height: 5.0kmIWC<0.4g/m3 LWC>0.4g/m3

Mature structure at 1827UTC Cell A’

Mature structure at 1827UTC Cell A’

1828.45 1826.45

SENW

A”A’

Cell A’:Particle imagesCell A’:Particle imagesCenter of A” Young developing cell

Center of A’ Mature cell

Liquid drops

Rough-edged graupel

Conclusions & Summary By Authors

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

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

Comments?!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…

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…

Thank YouThank You