Seismo-acoustic observation of the Éowyn impactful storm at Romanian infrasound and seismic arrays

Strong storms in the North Atlantic are a significant natural source of low-frequency seismic and acoustic signals (microseisms and microbaroms), commonly detected by monitoring stations in Romania. Storm Éowyn was an intense extratropical cyclone that impacted Ireland and the United Kingdom on 24 January 2025, driven by an exceptionally strong jet stream. The storm produced maximum wind gusts of 183 km/h and sustained winds of 135 km/h in western Ireland, breaking national records dating back to 1945.

This study presents a joint seismo-acoustic analysis of Storm Éowyn as an intense source of oceanic ambient noise, using simultaneous seismic and infrasonic observations from the Romanian arrays BURAR, BURARI, and IPLOR. Infrasonic and seismic data were processed using the PMCC correlation-based method to characterize the temporal variability of microbarom and microseism signals between 21 and 27 January 2025. Seismo-acoustic detections in the 0.1–0.6 Hz frequency range were analyzed with DTK-PMCC and DTK-DIVA software packaged into CTBTO NDC-in-a-Box.

The storm trajectory was computed using CyTRACK, an open-source Python toolbox for cyclone detection and tracking. ERA5 hourly reanalysis data from the Copernicus Climate Data Store provided mean sea level pressure, 10-m wind speed, and relative vorticity fields. Seismo-acoustic detections were compared with ARROW products from IFREMER describing microseism and microbarom source models. To assess detection performance and backazimuth discrepancies, we calculated the effective sound speed ratio (Ceff) at 50 km altitude using temperature and wind profiles from ECMWF operational analyses obtained via CAMS.

During the storm's peak impact on 24 January, power spectral density analysis revealed microbarometric peaks at 0.23 Hz (BURARI) and 0.22 Hz (IPLOR), while the microseismic peak at BURAR reached 0.29 Hz. Results demonstrate good agreement between observed signals and modeled source locations.

This study confirms the capability of Romanian infrasound and seismic arrays to monitor microbaroms and microseisms generated by intense North Atlantic storms. These findings provide a foundation for investigating other seismo-acoustic low-frequency signals from North Atlantic cyclones, which dominate winter detections at Romanian stations.