Lightning Imager

Data from the Lightning Imager will enable more precise forecasts of severe thunderstorms.

The imager detects all types of lightning: cloud-to-cloud, cloud-to-ground and intra-cloud flashes, thus providing an advantage over ground-based lightning detection networks. The LI is a new instrument on Meteosat, it has no heritage from the Meteosat Second Generation series.

The LI uses detector elements arranged in a detector array covering the whole Earth (no scanning mechanism).

The total energy received from the photons are sensed by each detector element and integrated during the integration period. These are then compared with the LI trigger threshold and if the energy exceeds this threshold, it is identified as an LI triggered event (Figure 1).

The Lightning Imager (LI), on board the MTG-I satellites, will continuously measure at a wave-length of 777.4nm with a very narrow bandwidth, with a spatial resolution 4.5km at sub-satellite point, triggered by a variable threshold — optical pulses initiated by lightning emitting energy of larger than between 4 and 7µJm-2sr-1.

The field of view (FOV) (Figure 2) of the LI instrument is covered by four identical cameras on the instrument, each covering one out of four domains on the observable Earth disc.

Products derived from the instrument data will be arranged around following three categories:

1. Events — what the instrument measures, a triggered pixel in the detector grid.
2. Groups — neighbouring events in the same integration period (1 ms), representing a lightning stroke.
3. Flashes — collection of groups in temporal and spatial vicinity (XXkm, YY milliseconds), representing a lightning flash.

The MTG-I LI instrument will complement the NOAA Geostationary Lightning Mapper (GLM) on the GOES-R and the GOES-S satellites and CMA Lightning Mapper onboard the FY-4 satellite series.