Observations in the Northwestern Mediterranean Region from the - PowerPoint PPT Presentation

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 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

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) Image: http://www.eumetrain.org/data/3/362/362.pdf Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 2 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 3 / 11

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 Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 4 / 11

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 Distance closest elements Time offset closest elements 2.5 km to 3.0 km (A) -0.5 ms to +0.5 ms (B) -1.0 ms to +1.0 ms 0.8 km to 2.8 km Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 5 / 11

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) (A) (B) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 6 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 7 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 8 / 11

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) (A) (B) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 9 / 11

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 (A) (B) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 10 / 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 Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 11 / 11

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 Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 12 / 11

Additional Slides

ISS-LIS and Meteorage: Relative Detection efficiency (DE) ➢ 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) (A) (B) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 14 / 11

Analyzed flash characteristics ➢ Flash matching algorithm (both 20 km, 1 sec) applied for flash elements 1 ISS-LIS flash ( LIS event) matched to 2 Meteorage flashes ( Meteorage pulse/stroke) ➢ 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 Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 15 / 11

Merging algorithms NASA LIS In-house Events<groups<flashes(<areas) Events<flashes 5.5 km / 330 ms Weighted Euclidean 10 km / 300 ms for events of a flash Distance for groups of a flash Both constraints must be met by at least WED² = (X/5.5)²+(Y/5.5)²+(T/330)²<1 two events of the same flash X: lat distance of group centroids [km] Y: lon distance of group centroids [km] T: time difference of groups [ms] (Mach et al., 2007) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 16 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 17 / 11

Flash durations – Matched vs unmatched flashes (A) (B) ISS-LIS Matched (A): 0.35 s Unmatched (B): 0.20 s (C) (D) Meteorage Matched (C): 0.22 s Unmatched (D): 0.11 s Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 18 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 19 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 20 / 11

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) Felix Erdmann 99th AMS Annual Meeting – ISS-LIS vs Meteorage vs SAETTA 21 / 11