Seismo-acoustic and GNSS observations of a record-breaking Black Sea storm: repurposing geophysical sensors for environmental monitoring

Abstract. In August 2024, a devastating storm struck Romania's Black Sea coast, setting new precipitation records and marking an unusual change relative to historical climate observations. To investigate this extraordinary event, we integrated non-conventional sensors (seismic, GNSS, infrasound, and satellite data) with ERA5 meteorological reanalysis to monitor storm dynamics. High-frequency (>30 Hz) seismic signals captured precipitation, while microseismic bands (0.1–1 Hz) reflected wave-induced ground motion. Analysis of infrasound data via unsupervised learning delineated periods of acoustic quiescence from storm-related activity. The temporal evolution of these infrasound states coincided with distinct patterns in seismic ground motion, suggesting a shared origin in the storm's atmospheric dynamics. The infrasound array also detected over 1100 signals in the 0.6–7 Hz band, matching lightning discharges observed by geostationary satellites. GNSS data recorded a buildup of precipitable water vapor that peaked concurrently with intense rainfall, following a multi-day increase that preceded the main storm phase. This study highlights the value of integrating diverse, non-traditional datasets to enhance the resolution and depth of storm analysis. Their combined use offers a more holistic understanding of storm evolution and supports future research on the potential role of multi-sensor observations in improving early-warning systems in vulnerable coastal regions.