Lightning Detechtion and Classification

ALDIS records and classifies lightning based on physical properties and temporal-spatial criteria. All lightning events are grouped in several steps and summarised into so-called flashes.

Maps with Strokes and Flashes

1. Events (All Discharges)

Events are understood to be every single registered electrical discharge, regardless of its type. ALDIS distinguishes between two main types:

Cloud-to-Ground Stroke (CG Stroke)
A single discharge from the cloud to the ground(cloud-to-ground discharge). These are often referred to as strokes.
Intra-Cloud Pulse (IC Pulse)
A discharge within the cloud (cloud-to-cloud discharge) that is not in contact with the earth. These impulses are part of purely atmospheric processes.

2. Flash-Grouping: How events become flashes

Several events that are close together (in terms of time and space) are grouped into so-called flashes. Again, a distinction is made between two main types:

CG Flash (Cloud-to-Ground Flash)
A group of CG strokes (cloud-to-ground discharges) that are considered to be part of the same lightning flash.
CC Flash (Cloud-to-Cloud Flash)
A group of IC pulses (cloud-to-cloud discharges) that together are considered to be a purely atmospheric flash.

3. Change in CG Flash classification since 1 January 2017

Until 31 December 2016, each IC Pulse was automatically assigned to a single CC Flash - regardless of whether it was connected to a CG Flash.

A new classification model has been in place since 1 January 2017:

IC Pulses can now be assigned to a CG Flash if they fulfil certain temporal and spatial criteria.
This means that a CG flash can also contain IC pulses in addition to CG strokes - provided they are part of the same flash process.

This leads to a more realistic representation of complex lightning processes, especially in the case of long-lasting or branched discharges.

Summarising terms

CG Strokes: Single discharges to earth
IC Pulses: Discharges within the cloud or between clouds
CG Flash: Flash with at least one CG stroke (can also contain IC pulses since 2017)
CC Flash: Flash with only IC pulses
Total Flashes: Sum of all CG Flashes and CC Flashes
All Events: Sum of all CG Strokes and IC Pulses