ThunderSeis: Seismic analysis of thunder infrasound (EMERGING FIELD GRANT 2018)

Thunder created during lightning storms are among the most striking physical phenomena that are experienced by the general public. The mechanisms behind their generation and propagation remain unclear, however. Studies suggest that infrasound observations can provide detailed insight into the mechanisms of thunder generation, yet infrasound recording stations have been sparse until recently.

Over the last months, striking observations have been made of infrasound propagating across Eastern Austria, using the seismological AlpArray network. Some of these strong signals were generated by the explosion of the Baumgarten gas hub on December 12, 2018. Clearly, dense seismic networks have much potential for studying infrasound signals, due to the seismo-acoustic coupling that turns atmospheric pressure signals into measurable ground motion.

We also observe strong signals of thunder, e.g. during the severe weather crisis on May 1, 2018, and we propose here to study thunder infrasound systematically. The AlpArray network provides wide coverage over a multi-year time span, suitable for studying those phenomena.

Very useful in this context will be the comprehensive Austrian lightning database ALDIS: it will allow comparing lightning detections with the thunder that is recorded on the seismic stations. This is a new and innovative approach that will allow us to gain insight into both thunder generation, regional infrasound propagation in the Alpine region, and seismo-acoustic coupling.

The seismoacoustic observations will illuminate processes that occur in the Atmospheric Boundary Layer (ABL), the lowest 1-2 km of the atmosphere. The ABL is the part of the atmosphere that is strongly influenced by the surface and the region where large parts of human, animal and plant life takes place.