Passive acoustic remote sensing and anomalous infrasound propagation studies

In this talk, we will present recent work on various infrasound remote sensing studies. We will focus on bi-directional stratospheric ducting during a Sudden Stratospheric Warming (SSW) event and the associated infrasonic signature. We present infrasound data in which the described effect is captured with microbarom signals in the Mediterranean region. Microbarom source locations are modeled using operational ocean wave models. The modeling reveals a previously unidentified microbarom source region in the Eastern Mediterranean besides the more typical microbarom source region in the Atlantic Ocean. This work illustrates that the classic paradigm of a unidirectional stratospheric duct for infrasound propagation can be broken during a SSW event. Furthermore, we will present a case study in which the influence of atmospheric dynamics on infrasound propagation is studied. We make use of over 6 years of nearly continuous volcanic infrasound recordings from Mount Etna, Italy (37 N) that are available through the Atmospheric dynamics Research InfraStructure in Europe (ARISE) network. The infrasound observables are compared to theoretical estimates obtained from propagation modeling using existing European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric databases. While a good agreement is often found, we also report on significant discrepancies around the equinox period and during intervals during which anomalous detections occur during the winter.