Preprints
https://doi.org/10.5194/egusphere-2024-2804
https://doi.org/10.5194/egusphere-2024-2804
14 Nov 2024
 | 14 Nov 2024
Status: this preprint is open for discussion.

Influence of the North Atlantic Oscillation on annual spatio-temporal lightning clusters in western and central Europe

Markus Augenstein, Susanna Mohr, and Michael Kunz

Abstract. Based on lightning measurements in western and central Europe from 2001 to 2021 (May–August), a grid-based climatology and trend analysis of thunderstorm activity has been developed. The results indicate a significant decrease in thunderstorm activity in many regions. Extending the analysis beyond a purely grid-based approach, areas with spatio-temporal intense lightning (convective clustered events, CCEs) were identified in a second step by applying a clustering algorithm (Spatio-Temporal Density-Based Spatial Clustering of Applications with Noise, ST-DBSCAN). For this purpose, a methodology is presented which seeks out to determine an appropriate density definition, as required by ST-DBSCAN.

An analysis of the characteristics of the CCEs indicates a slight increase of smaller, more separated clusters, while larger clusters occur less frequently over time. This suggests a shift in the mesoscale organization of convective systems. Furthermore, a correlation between the North Atlantic Oscillation (NAO) and thunderstorm frequency has been identified. Notably, there was a pronounced reduction of thunderstorm activity, as well as an increased number of separated convective systems during negative NAO phases in France. This, in conjunction with a documented accumulation of years with predominantly negative NAO values between 2011 and 2020, is likely a contributing factor to the aforementioned negative trends.

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Markus Augenstein, Susanna Mohr, and Michael Kunz

Status: open (until 26 Dec 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Markus Augenstein, Susanna Mohr, and Michael Kunz
Markus Augenstein, Susanna Mohr, and Michael Kunz

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Short summary
A grid-based analysis of lightning in Europe shows a reduction in thunderstorm activity in many regions. Moving away from a grid-based analysis, a spatio-temporal clustering algorithm was used. The results show a slight trend towards the occurrence of smaller, more separated convective clustered events, suggesting changes in the organization of convective systems. One reason for this could be the increased occurrence of the negative phase of the North Atlantic Oscillation in the last decade.