Observations of TLEs in winter Observations of TLEs in winter thunderstorms during the 2005-thunderstorms during the 2005-

2008 ILAN campaigns2008 ILAN campaigns

Yoav YairYoav Yair11, Colin Price, Colin Price22, Michal Ganot, Michal Ganot22, Eran Greenberg, Eran Greenberg22, Roy Yaniv, Roy Yaniv1,21,2, , Yosef SherezYosef Sherez22, Baruch Ziv, Baruch Ziv11, Na’ama Reicher, Na’ama Reicher22, Elyakom Vadislavsky, Elyakom Vadislavsky33, , Carynelissa ErlickCarynelissa Erlick33 and Adam Devir and Adam Devir1,41,4

1 The Open University of Israel

2 Tel-Aviv University

3 Hebrew University of Jerusalem

4 IARD, Nesher

Talk LayoutTalk Layout

• Winter thunderstorms - Refresher• The ILAN winter campaigns

– Single station observations 2004-2006– Two-Station observations 2007/8– ELF and VLF data 2004-2008Main Results

Optical propertiesMeteorological conditionsCalibrated measurements3D structure

• Summary • Future Research

Winter thunderstorms - climatologyWinter thunderstorms - climatology•Occur in very few places in Northern Hemisphere winter, mostly where cold air is transported above warm water

•Gulf Stream, Sea of Japan, Mediterranean Sea

•Land areas are almost completely devoid of thunderstorm activity

20062007

1999

Winter Sprites (refresher)Winter Sprites (refresher)

• So far, TLEs above winter thunderstorms have been observed exclusively in Japan (Fukunishi et al., GRL, 1999; Takahashi et al., JASTP, 2003; Hobara et al., 2003; Hayakawa et al., JGR, 2004; Adachi et al., GRL, 2004 and many newer papers)

• In Japan, TLEs are found in the winter monsoon regime, when cold Siberian air-masses flow from north-east above the warm Sea of Japan. The ensuing instability leads to the development of active Cumulonimbus clouds with a vertical dimension of 5-7km, embedded within larger (8,000-40,000km2) stratiform-like regions

• The analogy between the synoptic setting for winter thunderstorms in Japan and in the Eastern Mediterranean has already been noted (Levin et al., GRL, 1996; Yair et al., JGR, 1998; Altaratz et al., MWR, 2003) – cold air-masses from Europe move over the warm Mediterranean Sea.

ILAN winter campaigns (ISF, 2003-8)ILAN winter campaigns (ISF, 2003-8) • We observe storms and cold-fronts west of Israel as they

approach the coast

• 2003/4 Season – testing and system validation• 2004/5Season – Initial observations from Tel-Aviv

– No GPS, No tracking• 2005/6 Season observations from TAU and MR• 2006/7 and 07/08 Seasons – two stations, also East!

Cameras:Watec100N with a 12mm f/0.8 lens (PAL) FOV of 31.5˚x23Watec-902H with a 25mm f/1.4 lens (NTSC) FOV of 14˚x10.5˚

Real time event-detection software (UFO Capture), GPS time-stamp ELF and VLF data from Negev stations (MR, SB), NCK in Hungary Weather radar – real time, locating active cells (dBZ)

Weather forecast – decision on observation site based on viewing conditions as a function of cloud coverageReal-Time target acquisition based on BOLTEK lightning detection system (based @ TAU) and IR satellite images, also weather radar

http://geophysics.tau.ac.il/personal/ilan/

Tel-Aviv or Wise Observatory, Mizpe Ramon

Sites in the Negev Desert (Israel)

Mitzpe Ramon (ELF)Sde-Boker (VLF)

Geo-location of the parent lightning (Price et al., 2001; Greenberg et al, 2004).

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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L12801, doi:10.1029/2007GL029258, 2007

Satellite analysis: 13Jan06 12z USAFE OWS WebSite

Estofex: www.estofex.org

In 4 different winter storms we detected 30 events: 26 sprites and 4 elves. The detection ranges varied from 250 to 450 km. Sprites were found to be produced exclusively by +CGs that can be traced to active cells with a vertical dimension of 5–7 km and cloud top temperature of minus 40C, embedded in a much larger matrix of stratiform cloudiness.

date12-13.1.06(MR)

14-15.1.06(MR)

6-7.2.06(TA)

18-19.3.06(TA)

Total

sprites

2157226

elves12104

total3178230

Type# of eventsDistribution

Column (single)27.7%

Column (group)1142.3%

Carrot (single)311.5%

Carrot (group)623%

Undefined415.5%

ELF: All events have Qds between 200-2000 Qkm, related to +CG

Diffused light from cloud top

Sprite

β CepheusMag. 3.23

α CepheusMag. 2.44µ Cepheus

Mag. 4.08

ε DracoMag. 3.83 Observations from the

desert: clean sky, very low light pollution

Asymmetric Elves brightness

Enhanced convection associated with the left side of the exit of a jet streak

Synoptic: conditions for sprite-producing thunderstorms

Shallow upper-level trough with a weak surface low near Cyprus

Deep cyclone near Crete accompanied by upper level divergence, associated with positive vorticity advection ahead of the trough

Time delay between ELF transient from the parent flash and the Optically observed sprite: shorter delay for columns

Journal of Atmospheric and Solar-Terrestrial Physics 69 (2007) 1569–1586

9 TLEs in 24 minutes. All events were preceded by a clear transient in the SR band, indicating a +CG parent lightning

4 examples for non-TLEs producing CGs that occurred a few tens of seconds before and after SP+CG. No significant difference found compared to SP+CG!

Averaged (characteristic) spectral waveforms in frequency for the three EM field components Hns, Hew and Er typical of SP+CG flashes

The number of columns is positively correlated with the CMC (unlike Adachi et al., 2004)

Optical observations of transient luminous events associated with winter thunderstorms near the coast of Israel

Yoav Yair, Colin Price, Michal Ganot, Eran Greenberg, Roy Yaniv, Baruch Ziv,

Yosef Sherez, Adam Devir, Jo'zsef Bór, Gabriella Sátori

all sprites - high values

0500

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CM

C

observations:10

TLEs66

sprites56

Column (s)6

Column (g)29

Carrot (s)6

Carrot (g)11

Undefined sprite4

elves9

halos7

Undefined: halo/elve1

only column sprites

0500

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C

All the ELF signals were produced solely by positive cloud-to-ground flashes (+CGs), recorded in Israel (88%) and Hungary (77%). CMC average values of 1400±600 C·km, with some extreme events exceeding 3500 C·km

Accepted: Atmos. Res. 2008, special issue ICAE 2007, Beijing

VLF stations:

HWU (18.3 kHz; Le Blanc, France; 46.62°N, 01.08°E)

NAA (24.0 kHz; Cutler, Maine, US; 44.63°N, 67.28°W).

Crete (CR), Greece (35.31°N, 25.08°E)

Sde Boker (SB), Israel (30.86°N, 34.78°E)

Trying to identify the signature of 15 sprite-producing lightning discharges in the ELF and VLF bands observed during the 2005 Eurosprite campaign.

Main FindingsMain Findings

An ELF transient was not associated with sprite occurrence for 5 out of 15 events, suggesting that long continuing current of tens of msec may not always necessary for sprite production

For 6 out of 15 imaged sprites there was more than one parent +CG, implying that lightning discharges that produce sprites can sometimes have multiple ground connections separated in time and space (a few tens of msec and a few km respectively).

Column and carrot sprites cannot be identified by either their ELF or VLF signature alone, at least not at the distance to the source of several thousand km as preformed in the present study.

The 2007-8 winter campaignThe 2007-8 winter campaignDuring the winter of 2007-8 sprite campaign in Israel, observations

were conducted simultaneously from Jerusalem and Tel-Aviv / Mitzpe Ramon

20:25:40.669 Multiple downward leaders

Winter 2007-8 StatisticsWinter 2007-8 Statistics

JerusalemTel-Aviv / Mitzpe-Ramon

Type of TLE

1836Columns

86Carrots

88Mixed / Unidentified

06Elves

21Upward

3657Total

• 13 successful observation nights from Jerusalem: long range detection, weaker storms, low flash rate, few events

•4 successful nights from Tel-Aviv: severe light pollution

•1 successful night from MR (half of the data!)

Indication for a circular 3D Indication for a circular 3D arrangement of sprite columnsarrangement of sprite columnsThe appearance of the Sprite element in 3D varies with observation angle, leading to distortion of the circle from ellipse to straight line. We always see a projection in 2D.

The ratio of the small and large axis of the ellipse relates to sin δ, which is the angle from the observer’s horizon to the center

Stereoscopic measurements of sprites Stereoscopic measurements of sprites

A simultaneous image of a column cluster from Jerusalem and Tel Aviv taken on December 5th 2007. Severe light pollution precludes stereoscopic analysis.

01.0~0098.0~106.0

096.05.5

[3.25.23

][6.45

][6.447

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SIN

kmr

kmd

kmd

picpic

Hypothesis: a combination of an EMP preceding the QE field of +CG.

The EMP has a minimum directly above the lightning but increases as a function of r. The QE field has a maximum close to that axis and decreases with r2.

At some critical R the combined effect is sufficient for conventional breakdown.

An Electrostatic ApproachAn Electrostatic Approach

2

32222

32220 )(

)(

)(

)(

4),,(

Zszyx

Zsz

Zszyx

ZszQzyxEz

• A point charge above a conducting infinite plane simulates the electric field generated above a thunderstorm after the removal of positive charge from the cloud to the ground by an intense lightning discharge.

• The model is based on a solution for a 3D electrostatic image charge problem (Hiraki and Fukunishi, 2006): Q - total charge [Coulomb]

Zs – the height of the charge above the ground [km]

For each Qds configuration, we get a critical radius [km] at a specified altitude that matches the breakdown field [V/m] for that altitude.

Convergence and Convergence and curvature of sprite tendrilscurvature of sprite tendrils

• The upper part of the brightest bended carrot is tilted diagonally and oppositely with respect to the lower part

• The 4 Column sprites on the left-hand side also show some bending

• Cloud luminosity maximum indicates the location of the parent flash is offset with respect to the vertical carrot.

• Continuing the tendril direction leads to the location of the charge center.

The strength of bending might be related to the speed of development and/or delay from the parent CG (Y. Takahashi, P. Communication).

Calibrated spectral measurements of TLEs with the Calibrated spectral measurements of TLEs with the Watec 902H cameraWatec 902H camera

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Left Sprite: 269 KR*Right Sprite: 301 KR*

Talk will be given by R. Yaniv on Friday afternoon during the COST session

First Observation of Blue Jets (?) / Starters – from First Observation of Blue Jets (?) / Starters – from Jerusalem to a thunderstorm in Jordan. Range ~ 150 kmJerusalem to a thunderstorm in Jordan. Range ~ 150 km

Cloud top was at 11km, the length of the blue jet ~1 km. Total duration was 0.15 s

Clear dry air, little dust – excellent viewing conditions towards east.

Parent Flash starts at 28/4/2008 19:12:02.384

Summary and future workSummary and future work

• The MEIDEX kick-started sprite research in Israel and led to many fruitful international collaborations.

• ELF and VLF data are continuously collected and enable location of parent CGs for sprites anywhere (best for Europe and Africa)

• Future Plans: calibrated multi-spectral measurements, Additional new instruments and observation points, fully automated sprite tracking system (FAST).

Just outside the footprint of ISUAL..

Optical capacity building in our continued winter campaigns allows coverage of the entire region and offers extensive ground-truth for present and future space-based platforms (SpriteSat, Taranis, ASIM…)

AcknowledgementsAcknowledgements

This research was supported by the Israel Science Foundation grant 145/03 and by the Research Authority of the Open University

Thanks to EU COST Action P-18 Physics of Lightning, for enabling young scientists exchange with U. of Toulouse – M. Ganot and O. Van-der Velde

Thanks for your attentionThanks for your attention!!

ILAN is a continuation of the MEIDEX conducted by the first Israeli astronaut Ilan Ramon on the

space shuttle Columbia in STS-107, January 2003