Lightning!Lightning!

Memphis AMS/NWA Chapter Memphis AMS/NWA Chapter meetingmeeting

March 23, 2010March 23, 2010

OverviewOverview

History of electrificationHistory of electrification Charge development and lightning Charge development and lightning

formationformation Measurement toolsMeasurement tools

National Lightning Detection NetworkNational Lightning Detection Network Lightning Mapping ArraysLightning Mapping Arrays SatelliteSatellite

Current researchCurrent research Severe weatherSevere weather Lightning warnings/cessationLightning warnings/cessation

Lightning: A brief historyLightning: A brief history Benjamin Franklin Benjamin Franklin

performed the first study of performed the first study of lightning in September lightning in September 1751.1751. Kite experiment May 10, 1752Kite experiment May 10, 1752

This experiment was This experiment was successfully repeated in successfully repeated in 1752 by French scientist 1752 by French scientist Thomas Francois D'Alibard Thomas Francois D'Alibard

In July 1753 Swedish In July 1753 Swedish scientist G. W. Richmann scientist G. W. Richmann was killed when trying to was killed when trying to recreate the Franklin recreate the Franklin experiment.experiment.

Little was done between the Little was done between the late 1700s until the early late 1700s until the early 1900s1900s

Image adapted from MacGorman and Rust (1998) The Electrical Nature of Storms

Lightning: a brief historyLightning: a brief history C.T.R. Wilson was the first to C.T.R. Wilson was the first to

use electric field use electric field measurements to estimate the measurements to estimate the structure of thunderstorm structure of thunderstorm charges involved in lightning charges involved in lightning discharges. discharges. Wilson formulated the Wilson formulated the

hypothesis that a hypothesis that a thunderstorm consisted of a thunderstorm consisted of a dipoledipole

Wilson also won the Nobel Wilson also won the Nobel Peace Prize for the creation of Peace Prize for the creation of his cloud chamberhis cloud chamber

Lightning research took off in Lightning research took off in the early 1960s with the the early 1960s with the development of the space development of the space programprogram

Image adapted from www.nobelprize.org

Charge DevelopmentCharge Development

The non-inductive The non-inductive charging mechanism charging mechanism primarily responsible primarily responsible for thunderstorm for thunderstorm charging.charging. Temperature difference Temperature difference

causes charge differencecauses charge difference

Collisions cause charge Collisions cause charge separationseparation

Sign of charge Sign of charge transferred depends on:transferred depends on:

temperaturetemperature effective liquid water effective liquid water

contentscontents rime accretion raterime accretion rate relative velocity between relative velocity between

particles particles Figure above adapted from Saunders (1993)

Combination of results from Takahashi (1978) and Saunders et al. (1991)

Lightning FormationLightning Formation

3/6+ Step process3/6+ Step process CoronaCorona Stepped LeaderStepped Leader

50 m jumps, tip of 50 m jumps, tip of leader is corona pointleader is corona point

Cloud to Ground also Cloud to Ground also includesincludes Upward LeaderUpward Leader Junction processJunction process Return strokeReturn stroke dart leaderdart leader

dart stepped leaderdart stepped leader

VIDEO(S)VIDEO(S) http://www.ztresearch.com/http://www.ztresearch.com/

Interferometer measurement of in cloud lightning. Adapted from Shao and Krehbiel (1996)

Lightning Lightning MeasurementsMeasurements

National Lightning National Lightning Detection NetworkDetection Network

First developed in the First developed in the early 1980searly 1980s

Originally used TOA Originally used TOA system (LPATS)system (LPATS)

Direction finder Direction finder network created by network created by early 1990searly 1990s 2 antennas2 antennas

Companies merged, Companies merged, and merged systems, and merged systems, and now this is owned and now this is owned by Vaisala, Inc. by Vaisala, Inc.

New sensor is a New sensor is a combination of bothcombination of both IMPACT sensor (left)IMPACT sensor (left)

Images courtesy www.nasa.gov

3-D Lightning Mapping3-D Lightning Mapping

Above – The Northern Alabama 3-D VHF Lightning Mapping Array VHF antenna locations (green dots). Image provided by the NASA SPoRT (Short-term Prediction Research and Transition Center) website. (http://www.ghcc.msfc.nasa.gov/sport/)

Adapted from Thomas et al. (2004) depicting a lightning flash in space and time. Cool colors represent the early parts of the flash, while warmer colors indicate flash propagation in the latter part of the flashes history

Lightning mapping arrays measure the electrical breakdown process using VHF sources in 80 μs intervals to detect lightning in three dimensions

Operates using TV channel 5 (76-82 MHz)

Accuracy out to 150 km, <50 m

LMA Flash examplesLMA Flash examples

Movies taken from: http://branch.nsstc.nasa.gov/public/LMA/archive/imagery/

March 30 2002, 0809 UTC March 30 2002, 0819 UTC

Precursors to the Precursors to the Satellite EraSatellite Era

Video taken from the space shuttle over Argentina.

Courtesy Dr. William Koshak, MSFC

U2 observation of a thunderstorm over Georgia, in June 1983.

Vonnegut et al. (1989)

Satellite Satellite ObservationsObservations

Lightning can be observed Lightning can be observed from space from space

Two satellites have been Two satellites have been used to observe lightningused to observe lightning Tropical Rainfall Measuring Tropical Rainfall Measuring

MissionMission Optical Transient DetectorOptical Transient Detector

Uses a thin oxygen line to Uses a thin oxygen line to observe lightning flashesobserve lightning flashes

Future real time Future real time observations of total observations of total lightning will be on the lightning will be on the GOES-R satellite GOES-R satellite

(Images courtesy www.nasa.gov)

Tropical Rainfall Measuring Mission Satellite

Total lightning observed by TRMM

Part 3: Current ResearchPart 3: Current Research

KBMX

RSA

68 km

KGWX

UAH/NSSTC THOR Center and Hazardous Weather Testbed

MIPS/NSSTC

ARMOR

KHTX

75

DD lobe

1 km Res.

1.5 km Res.

LMA 100-500 m

LMA Antenna

NEXRAD

ARMOR

MIPS Profiler

MAX ?

MAX

21442144

Correlating LightningCorrelating Lightningto Severe Weatherto Severe Weather

Goodman et al. 1988 Goodman et al. 1988 demonstrated that total demonstrated that total lightning peaked prior to lightning peaked prior to the onset of a the onset of a microburst microburst

Williams et al. 1989 Williams et al. 1989 showed that the peak showed that the peak total flash rate total flash rate correlated with the correlated with the maximum vertical extent maximum vertical extent of pulse thunderstorms, of pulse thunderstorms, and preceded maximum and preceded maximum outflow velocity by outflow velocity by several minutesseveral minutes Adapted from Williams et al. (1989)

Adapted from Goodman et al. (1988)

Previous WorkPrevious Work

Williams et al. (1999) Williams et al. (1999) once again illustrates once again illustrates the usefulness of the usefulness of total lightning data in total lightning data in determination of determination of storm severity in storm severity in Florida Florida thunderstorms.thunderstorms.

Williams also Williams also proposed 60 flashes proposed 60 flashes minmin-1-1 or greater for or greater for separation between separation between severe and non-severe severe and non-severe thunderstorms.thunderstorms.

Adapted from Williams et al. (1999)

Overall Goals – Lightning Overall Goals – Lightning Jump Algorithm Jump Algorithm

1.1. Build on the lightning Build on the lightning jump framework set jump framework set through previous studies.through previous studies.

2.2. Understand what Understand what typically occurs in non-typically occurs in non-severe convection with severe convection with respect to increases in respect to increases in lightning.lightning.

3.3. Ultimately develop a Ultimately develop a lightning jump algorithm lightning jump algorithm for use on the for use on the Geostationary Lightning Geostationary Lightning Mapper (GLM)Mapper (GLM)

Also for NWS offices with Also for NWS offices with ground based lightning ground based lightning mapping networks mapping networks available.available.

Adapted from Williams et al. (1999)

Severe Weather Severe Weather ExamplesExamplesApril 4, 2007, 0245-

0345 UTCSeptember 25, 2005 1800-2030 UTC

Null Examples/Null Examples/False AlarmsFalse Alarms

June 14, 2005

LMA Source Data 15 -17Z

19 June 2007

Lightning Jump Algorithm Lightning Jump Algorithm UpdateUpdate

367 thunderstorms analyzed so far 367 thunderstorms analyzed so far from from

3 different regions of the country3 different regions of the country 111 severe, 256 non severe111 severe, 256 non severe

Best skill from the 2 sigma Best skill from the 2 sigma configurationconfiguration

NWS skill scores for all severe weather (80-90% POD; NWS skill scores for all severe weather (80-90% POD; FAR ~48%)FAR ~48%)

Average Peak flash rate of non Average Peak flash rate of non severe thunderstorms about 10 severe thunderstorms about 10 flashes per minuteflashes per minute

Next steps:Next steps: Look at other regions of the countryLook at other regions of the country Examine warning summaries from Examine warning summaries from

NWS to compare to jump signaturesNWS to compare to jump signatures Explore combinations of algorithms Explore combinations of algorithms

to see if there is any improvement in to see if there is any improvement in the skill scoresthe skill scores

Gatlin Gatlin 2 Sigma2 Sigma 3 Sigma3 Sigma Threshold 4Threshold 4 Threshold 5Threshold 5

PODPOD 0.910.91 0.850.85 0.580.58 0.700.70 0.700.70

FARFAR 0.740.74 0.470.47 0.400.40 0.580.58 0.550.55

CSICSI 0.250.25 0.480.48 0.420.42 0.360.36 0.380.38

HSSHSS 0.400.40 0.650.65 0.590.59 0.530.53 0.550.55

Lightning Warning Lightning Warning ProductsProducts

D. Buechler, NASA, MSFC/UAHuntsville

Lightning Lightning CessationCessation

Polarimetric Radar

1. Reflectivity factor Z at horizontal (Zh) or vertical (Zv) polarization [Conventional radar measure]

- Measure of drop size and concentration;

• Most sensitive to drop SIZE (D6)

2. Differential reflectivity ZDR a ratio of returned power: (Zh/Zv)

- Measure of median drop diameter→ SIZE/SHAPE

- Useful for rain / hail / snow discrimination→ SIZE/SHAPE

3. Propagation differential phase, DP, and from it,

specific propagation differential phase KDP (kh – kv)

- Measure of water content and drop size→ NUMBER/SHAPE

- Immune to radar calibration, attenuation, partial beam blockage

4. Correlation coefficient ρhv

- Indicator of mixed precipitation → SHAPE/PHASE/CANTING (Depolarization)

- Useful for identifying non-meteorological scatterers too!Advantages: Better description of various particle types/shapes in a given volume

• Determine size distribution- more accurate rain rates (improved QPE)

• Hydrometeor ID and non-meteorological scatterers (clutter!)

• Consistent calibration

Zh, kh

Zv, kv

We need the measurement in H and V directions!

Walter A. Petersen NASA MSFC VP-61

Variables……..

BackgroundBackground Past research has shown strong evidence for Past research has shown strong evidence for ice crystal ice crystal

orientation signatures in polarimetric radarorientation signatures in polarimetric radar [[differential differential phasephase] ] observations of thunderstorms (e.g., Hendry and McCormick observations of thunderstorms (e.g., Hendry and McCormick 1976, 1979; Hendry and Antar 1982; Krehbiel et al. 1991, 1992, 1996; 1976, 1979; Hendry and Antar 1982; Krehbiel et al. 1991, 1992, 1996; Metcalf, 1992, 1995; Metcalf, 1992, 1995; Caylor and Chandrasekar 1996Caylor and Chandrasekar 1996; ; Galloway et al. Galloway et al. 19971997; ; Scott et al. 2001; Marshall et al. 2009Scott et al. 2001; Marshall et al. 2009).).

Theoretical work by Weinheimer and Few (1987) demonstrated Theoretical work by Weinheimer and Few (1987) demonstrated that that ice crystals up to 1-2 mm could be vertically aligned by ice crystals up to 1-2 mm could be vertically aligned by strong vertical electric fields strong vertical electric fields (E-fields) of about 100-200 kV m(E-fields) of about 100-200 kV m-1-1. .

Strong motivation for our ongoing work is provided by Krehbiel et Strong motivation for our ongoing work is provided by Krehbiel et al. (1993): al. (1993): ““[polarimetric radar] signatures have been found to provide an [polarimetric radar] signatures have been found to provide an excellent indicator of the potential for lightning in a storm and we excellent indicator of the potential for lightning in a storm and we have used them to predict the occurrence of numerous lightning have used them to predict the occurrence of numerous lightning discharges. The [polarimetric] measurements have also been used discharges. The [polarimetric] measurements have also been used to detect the initial electrification of storms and to determine to detect the initial electrification of storms and to determine when a storm is finished producing lightning.”when a storm is finished producing lightning.”

Radar differential phase Radar differential phase (specific differential phase, K(specific differential phase, Kdpdp, and its , and its integral integral dpdp or PHIDP) or PHIDP) is is currentlycurrently measured by many measured by many research research (e.g., UAH-NASA ARMOR C-band, UAH MAX X-band) (e.g., UAH-NASA ARMOR C-band, UAH MAX X-band) and operational and operational (e.g., new 45WS CCAFS-KSC Radtec TDR (e.g., new 45WS CCAFS-KSC Radtec TDR 43‑250 C-band) 43‑250 C-band) radarsradars..

L. D. Carey, ESSC, ST2009

6.2 km

7.2 km

DP

DP

6.2 km

7.2 km

DP

DP

Hei

gh

tTime

Sector scans: Examine time and height changes in ice orientation (change of DP with range-red circle) in a lightning-producing cloud. [UAH X-band dual-pol data from August 18, 2009].

1630 UTC 1632 UTC

Before flash After flash

Useful LinksUseful Links

http://www.nsstc.uah.edu/atmos/http://www.nsstc.uah.edu/atmos/ http://http://

www.nsstc.uah.edu/ARMOR/webimagewww.nsstc.uah.edu/ARMOR/webimage//

http://weather.msfc.nasa.gov/sport/lmahttp://weather.msfc.nasa.gov/sport/lma//

http://thunder.msfc.nasa.gov/http://thunder.msfc.nasa.gov/ http://www.srh.noaa.gov/mlb/?n=total_http://www.srh.noaa.gov/mlb/?n=total_

lightninglightning http://www.srh.noaa.gov/srh/jetstream/http://www.srh.noaa.gov/srh/jetstream/