During thunderstorm activity in the Netherlands, electromagnetic and infrasonic signals are emitted due to the process of lightning and thunder. It is shown that correlating infrasound detections with results from a electromagnetic lightning detection network is successful up to distances of 50 km from the infrasound array. Infrasound recordings clearly show blastwave characteristics which can be related to cloud-ground discharges, with a dominant frequency between 1-5 Hz. Amplitude measurements of CG discharges can partly be explained by the beam pattern of a line source with a dominant frequency of 3.9 Hz, up to a distance of 20 km. The ability to measure lightning activity with infrasound arrays has both positive and negative implications for CTBT verification purposes. As a scientific application, lightning studies can benefit from the worldwide infrasound verification system

Typical infrasound best beam during nearby lightning activity. The best beam shows several blastwaves, which are associated with lightning discharges. The lower plot shows the time-frequency representation of the best beam, using the S-transform.

Reference:
Assink, J.D., L.G. Evers, I. Holleman and H. Paulssen, Characterization of infrasound from lightning Geophys. Res. Lett., 2008, 35, L15802, doi:10.1029/2008GL034193.