11.C - Other Natural Sources

Within NFR 11.C - Other Natural Sources: Other, natural activities and resulting emissions other than volcanoes (11.A) and forest fires (11.B) are to be taken into account.

For the time being, the only natural emission source reported within NFR 11.C is lightning.

As NFR 11.C is a memo item category, emissions reported here are not accounted for in the National Totals.

Lightning (and corona discharge) during thunderstorm events cause atmospheric chemical reactions to take place at high voltages and high temperatures. These reactions cause the production of NO_x in the atmosphere.

The calculation of NO_x emissions from lightning uses strike counts from the German weather service and default emission factors from the 2023 EMEP/EEA guidebook ¹⁾.

For the complete time series, the emissions are calculated as follows:

The number of lightning strikes in Germany is taken from a commercial system called “BLIDS” run by Siemens. The data has been cross-referenced with information from the German weather service. Consistent strike count data is available from 1992 onward and has been back-populated to cover the full time series since 1990. The following table shows the strike figures over time.

Table 1: Lightning strikes in Germany from 1990 onwards

For the calculation of emissions in this category, the Guidebook emission factor of 2.75 kg NO_x per strike is used.

The emission value is solely dependent on the strike count and varies between 1 to 3 kilotons of NO_x per year.

Figure 1: NFR 11.C, NO_x emissions from lightning

The AD from BLIDS does have a low uncertainty of ± 3%. The uncertainties for the emission factors are estimated to be relatively high, being a default value. Hence the overall uncertainty for the emission estimation of NO_x from lightning is qualified estimated by expert judgement to be high (>50%).

No sector-specific quality checks are done.