Global Microbarom Patterns: A First Confirmation of the Theory for Source and Propagation. Issue 3 (27th January 2021)

• Record Type: Journal Article
• Authors: De Carlo, Marine; Hupe, Patrick; Le Pichon, Alexis; Ceranna, Lars; Ardhuin, Fabrice
• Is Part Of: Geophysical research letters. Volume 48:Issue 3(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-01-27
• Subjects: ambient noise -- infrasound -- microbaroms -- wave modeling; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL090163
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Microbarom signals are generated by wind waves at the ocean surface and propagate all around the globe through the stratosphere and ionosphere. Microbaroms dominate the coherent infrasound ambient noise measured worldwide, with a peak around 0.2 Hz. Monitoring these signals allows characterizing the source activity and probing the properties of their propagation medium, the middle atmosphere. Here, we show the first quantitative validation of global microbarom modeling based on ocean wave models, a new source model and atmospheric attenuation. For evaluating these parameters' impact, we compare the modeling results with a global reference database of microbaroms detected by the infrasound International Monitoring System over 7 years. This study demonstrates that the new source model improves the prediction rate of observations by around 20% points against previous models. The performance is enhanced when the new model is combined with a wind‐dependent attenuation and an ocean wave model that includes coastal reflection. Plain Language Summary: Microbaroms are atmospheric ambient noise below the human hearing threshold. They are generated by ocean waves and can be detected by infrasound sensors worldwide. A better understanding is important because microbaroms could hide signals of interest in the context of the Comprehensive Nuclear‐Test‐Ban Treaty, established to unveil clandestine nuclear explosions worldwide. Furthermore, as microbaroms propagate over long ranges through the middle atmosphere, a better knowledge of the received signals provides new insights of middle atmosphere dynamics features that are unresolved in global circulation models. In this study, we use a historical database of microbarom detections to evaluate state‐of‐the‐art models and propose a methodology to simulate microbaroms worldwide. Key Points: A methodology to predict microbarom arrivals and to compare them with observations is presented Performances between two source models accounting for bathymetry, two propagation attenuations, and two wave models are compared In more than 90% of the cases, the source model performs better with a radiation depending on the elevation angle than with a monopolar one