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Image: https://directory.eoportal.org/web/eoportal /satellite-missions/iss-lis Concurrent Satellite and Ground-Based Lightning Observations in the Northwestern Mediterranean Region from the Optical Lightning Imaging Sensor (LIS), Low-Frequency

SLIDE 1

Concurrent Satellite and Ground-Based Lightning Observations

in the Northwestern Mediterranean Region from the Optical Lightning Imaging Sensor (LIS), Low-Frequency Meteorage and Very High-Frequency SAETTA Felix Erdmann; Olivier Caumont; Eric Defer; Richard J. Blakeslee; Stéphane Pédeboy; Sylvain Coquillat PhD Funding: CNES and Météo France

Image: https://directory.eoportal.org/web/eoportal /satellite-missions/iss-lis

SLIDE 2

Thesis Objective

➢Using Meteosat Third Gen. (MTG) Lightning Imager (LI) data in NWP (2021) ➢Assimilation of (synthetic) geostationary MTG-LI lightning observation ➢Simulate MTG-LI data (lightning proxy function) from ground-based data ➢Understand optical signals from lightning flashes using existing observations ➢Inter-comparison of ➢Optical LEO ➢Ground: Low frequency (LF) and Very high frequency (VHF)

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Image: http://www.eumetrain.org/data/3/362/362.pdf

99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA

SLIDE 3

Lightning observation instruments

➢Optical (777.4 nm) ISS-LIS as LEO ➢Low Frequency (LF) Meteorage network (similar NLDN) ➢Very High Frequency (VHF) SAETTA Lightning Mapping Array (LMA) ➢Viewtime of ISS-LIS + spatial and temporal coincidence

(A) (B)

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SLIDE 4

Data and Methods

➢Region: NW-Mediterranean, Corsica ➢Period: March 01, 2017 – March 20, 2018 ➢851 ISS overpasses – only 26 with ISS-LIS lightning activity ➢ISS-LIS events, Meteorage CG strokes and IC pulses ➢Events or pulses/stroke merged to flashes (new algorithm) ➢Identification of coincident flashes (matches) Flashes Discharge signals ISS-LIS 330 16,881 events Meteorage 569 2,144 (487 CG, 1657 IC) SAETTA N/A 274,871

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ISS-LIS and Meteorage: Relative detection

Relative Detection efficiency (DE): ➢ISS-LIS: 57.3 % of 569 Meteorage flashes ➢Meteorage: 83.3 % of 330 ISS-LIS flashes

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(A)

2.5 km to 3.0 km 0.8 km to 2.8 km

0.5 ms to +0.5 ms
1.0 ms to +1.0 ms

(B)

Distance closest elements Time offset closest elements

99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA

SLIDE 6

ISS-LIS minimum flash altitude

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Average minimum altitude: matched (A) < unmatched (B) (→ Meteorage DE)

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(A) (B)

99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA

SLIDE 7

ISS-LIS mean flash altitude and flash radiance

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Average mean flash altitude: matched (A) = unmatched (B)

(A) (B)

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SLIDE 8

ISS-LIS mean flash altitude and flash radiance

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Average mean flash altitude: matched (A) = unmatched (B) ➢Mean radiance increases with altitude

(A) (B)

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SLIDE 9

Meteorage maximum flash altitude + maximum amplitude

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Meteorage-only flashes (B) with lower altitude (ISS-LIS DE problem)

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(A) (B)

99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA

SLIDE 10

Meteorage maximum flash altitude + maximum amplitude

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Meteorage-only flashes (B) with lower altitude (ISS-LIS DE problem) ➢Maximum current negative for low altitude flashes

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(A) (B)

99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA

SLIDE 11

Conclusions

➢57.3 % ISS-LIS and 83.3 % Meteorage relative DE ➢Collocated flashes of ISS-LIS and Meteorage with good spatial and temporal agreement ➢Meteorage: reduced DE of flashes restricted to mid and high altitudes ➢ISS-LIS: significantly better DE for flashes exceeding 10 km of altitude than for the flashes restricted to lower altitudes ➢ISS-LIS event radiance and Meteorage pulse/stroke amplitude + polarity might serve for indirect altitude information ➢Limited number of cases due to LEO → ongoing GLM and NLDN comparison ➢Following steps: Lightning proxy function: LF to optical satellite signal Simulation of MTG-LI data over Europe

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SLIDE 12

References

➢Erdmann et al.: „Concurrent Satellite and Ground-Based Lightning Observations in the North-Western Mediterranean Region from the Optical Lightning Imaging Sensor (LIS), Low Frequency Meteorage and Very High Frequency SAETTA”, to be submitted in AMT Europe ➢Mach et al.: „Performance assessment of the Optical Transient Detector and Lightning Imaging Sensor“, Journal of Geophysical Research, Vol. 112, D09210, doi:10.1029/2006JD007787, 2007

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SLIDE 13

Additional Slides

SLIDE 14

➢ISS-LIS: 57.3 % of 569 Meteorage flashes ➢Meteorage: 83.3 % of 330 ISS-LIS flashes ➢4 categories – no one-to-one correspondance for matches 1 ISS-LIS flash ( LIS event) matched to 2 Meteorage flashes ( Meteorage pulse/stroke)

ISS-LIS and Meteorage: Relative Detection efficiency (DE)

(A) (B)

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SLIDE 15

➢Flash matching algorithm (both 20 km, 1 sec) applied for flash elements ➢Compare flashes with match to unmatched flashes ➢Number of elements (events, pulses/strokes) per flash, flash extent, flash duration, flash mean absolute (pulse/stroke) amplitudes and individual pulse/stroke amplitudes, flash mean (event) radiance, flash maximum (event) radiance ➢Using concurrent SAETTA VHF sources: Flash mean altitude, flash minimum altitude and flash maximum altitude 1 ISS-LIS flash ( LIS event) matched to 2 Meteorage flashes ( Meteorage pulse/stroke)

Analyzed flash characteristics

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SLIDE 16

Merging algorithms

NASA LIS Events<groups<flashes(<areas) 5.5 km / 330 ms Weighted Euclidean Distance for groups of a flash WED² = (X/5.5)²+(Y/5.5)²+(T/330)²<1 X: lat distance of group centroids [km] Y: lon distance of group centroids [km] T: time difference of groups [ms] (Mach et al., 2007) In-house Events<flashes 10 km / 300 ms for events of a flash Both constraints must be met by at least two events of the same flash

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SLIDE 17

Flash durations – Matched vs unmatched flashes

(A) (B)

ISS-LIS

Matched (A): 0.35 s Unmatched (B): 0.20 s ➢Stacked histograms – Day + Night and CG + IC ➢Mean flash duration: Matched flashes (A) longer than unmatched flashes (B)

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SLIDE 18

(A) (B)

Flash durations – Matched vs unmatched flashes

(C) (D)

Meteorage

Matched (C): 0.22 s Unmatched (D): 0.11 s

ISS-LIS

Matched (A): 0.35 s Unmatched (B): 0.20 s

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SLIDE 19

ISS-LIS minimum flash altitude and maximum event radiance per flash

➢Flash characteristics – Matched vs Unmatched flashes ➢altitude levels of concurrent SAETTA sources ➢LIS-only flashes higher minimum altitude (Meteorage issue) ➢Highest event radiance constant for flash minimum altitude bins

(A) (B)

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SLIDE 20

Meteorage minimum flash altitude + maximum amplitude

➢Flash characteristics – Matched (A) vs Unmatched (B) flashes ➢Altitude levels of concurrent SAETTA sources ➢Meteorage-only flashes (B) with lower altitude (ISS-LIS DE problem) ➢Maximum current negative for low altitude flashes

(A) (B)

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SLIDE 21

DE-dependency on the altitude

➢ISS-LIS for flashes > 10 km maximum altitude: 75.4 % (187 of 248 Meteorage flashes detected) ➢ISS-LIS for flashes <= 10 km maximum altitude: 45.3 % (105 of 232 Meteorage flashes detected) ➢Meteorage for flashes <= 6 km minimum altitude: 89.7 % (113 of 126 Meteorage flashes detected) ➢Meteorage for flashes > 6 km minimum altitude: 82.7 % (143 of 173 Meteorage flashes detected)

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