| 29 Jun 2026
Meteosat Third Generation Lightning Imager Detection Performances
Abstract. The EUMETSAT Meteosat Third Generation Lightning Imager (MTG-LI) is the brand-new European space-based lightning location system devoted to the diagnostic and characterization of lightning activity over hemispheric scale. In this publication, we present the assessment of MTG-LI detection performances against three different reference systems: the Vaisala Global Lightning Detection Network (GLD360), the European Consortium for Lightning Detection (EUCLID), and Geostationary Lightning Mappers (GLMs) -16 and -19 aboard NOAA GOES satellites. The analysis period is of eighteen months: from July 2024 to December 2025. MTG-LI flash detection efficiency varies between 70 % (day) and 95 % (night), with an average value of 87.4 %. Its average flash false alarm rate is generally below 0.5 flashes per second, while the average fraction of false flashes is 0.16 % of the total flashes. Finally, both average timing and location accuracy are presented and discussed.
Competing interests: At least one of the (co-)authors serves as editor for the special issue to which this paper belongs.
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This manuscript is an excellent description of the LI data and system. I believe this manuscript, once published, will be one of the first papers to be read by anyone wanting to use the LI data. The links to the user guide and software will be quite useful to users of the LI data. As such, I have been a bit "picky" about my suggestions so that the manuscript will be the best it can be. I suggest it be published with very minor revisions.
Specific Minor Issues
Line 1: delete “brand-new”.
Line 17: add comma after “(Grebovi´c et al., 2025)”.
Line 19: add comma after “(or location accuracy)”.
Line 26: replace “two big families” with “two major families”.
Lines 31-32: Need a reference for the statement starting with “The accuracy with which such systems describe…”.
Line 32: replace “LF and VLF LLSs one gets…” with “LF and VLF LLSs one gains…”.
Line 40: using the phrase “visible photons” implies that the optical signals from lightning detected by the LI are in the visible range. The ones I am familiar with are near-infrared, outside of the visible range. I would simply delete the word “visible” and add a phrase about the optical signal usually being in the near-infrared (and the specific spectral line at 777.4 nm).
Line 42: same issue as in line 40. Remove the word “visible”.
Line 42: the authors should reference the work of Koshak and others (e.g., DOI: 10.1175/JTECH-D-14-00085.1) that use statistical methods to estimate the IC/CG ratio of satellite based lightning data.
Line 53: replace “flying aboard” with “on”.
Line 56: replace “globe since several” with “globe for several”.
Line 60: replace “Table 1 resumes” with “Table 1 presents the”.
Line 62: The statement starting with “Space-based geostationary LLSs are superior to…” needs a reference to support it.
Line 80: replace “sense optical photons emitted in correspondence of lightning” with “sense optical photons emitted by lightning”.
Lines 82-83: this statement about the optical band for LI should be included in the discussion of the other orbital optical instruments, since they use the same oxygen triplet emission line.
Line 84: The authors should also provide the spatial sampling range of LI (from 4.5 km at nadir to X km near the edges of the detectors). Note, the second figure from Figure 1 in the LI user guide (https://user.eumetsat.int/resources/user-guides/mtg-li-level-2-data-guide) would be perfect.
Line 94: comma after “direct sunlight”.
Lines 108-110: the authors should state if the lightning locations are computed to the ground or some other “lightning ellipse”. The authors should also state if the times of the lightning are corrected for time of flight. Both of these bits of information are critical for users wanting to analyze the lightning data from LI.
Line 118: the authors should also state if the individual events are made available to the public and if those events are geolocated (to what altitude) and if they are time of flight corrected. The GLMs and LISs provide geolocated, time of flight corrected event data.
Line 118: At the end of this paragraph would be a good place to state if the data in the group and flash products are time of flight corrected.
Lines 129-131: Are there filters in the LI processing stream that remove known non-lightning sources?
Line 194: thank you for providing a link to code to correct time of flight and parallax.
Line 257: The authors should add an additional figure showing the overall distribution of location accuracy represented by Figure 5 (a single distribution with the X axis being km and the Y axis being counts).
Line 261: The authors should add an additional figure showing the overall distribution of time accuracy (a single distribution with the X axis being ms and the Y axis being counts).
Line 329: add a comma after “above 50◦ N” and after “FDE ≈ 80%”.
Line 378: remove the word “also”.
Line 380: remove the word “also”.
Line 431: remove comma after “et al.” and add “(“.
Lines 447-448: the sentence starting with “MTG-LI TA…” is confusing in its present form. I am not sure how to fix it, but please try to reword it. Maybe “MTG-LI TA is less than 1 ms over the entire reference period except for a few episodes of limited temporal duration.” My suggestion may not convey what you wanted, so you should try your own fix.
Line 448: change the phrase “…are related with outages…” to “…are related to outages…”.
Line 459: replace the phrase “…deviations from this mean pattern are met only on a limited number of…” with “…deviations from this mean pattern occur only in a limited number of…”
Lines 466-468: It would be interesting to recompute the overall FFAR values excluding those time periods (and locations) where there are known problems with the LI processing. It would provide the reader with more of the “true” FFAR value for LI.
Figure 3: Please make the various lines in the figure thicker. It will make them easier to read.
Figure 4: as mentioned earlier, the authors should add a line plot (extra figure) showing the distribution of LA for the whole dataset.