Towards an understanding of the microbarom source

Although currently not fully established, the infrasound network of the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty organization allows studies on a global scale, dealing with various topics like detection capability simulation, continuous monitoring of the atmosphere, or atmosphere/ocean interface modeling. The infrasonic background noise plays a dominant role in the selection of signals of interest especially near 0.2 Hz where the noise amplitude increases due to microbarom signals. The study of microbarom sources therefore helps improving the detection of nuclear explosions and volcanic eruptions, and allows microbarom detections to be used as continuous sources for monitoring atmospheric dynamics.

At a global scale, continuous infrasound monitoring from 2006 to 2010 provides monthly localizations of microbarom sources. These results, obtained with a multi-year averaging approach and a simple cross-bearing method, exhibit clear seasonal trends consistent with annual climate variations. At regional scales, the interpretation of microbarom observations at a single station remains challenging. For IMS stations between 2008 and 2009, we try characterise microbarom detections using a source model derived from wave interaction maps and the ECMWF wind model. This attempt highlights uncertainties when comparing microbarom modeling with observations. However, both statistical and quantitative approaches for microbarom studies provide new insights on quantitative relationships between infrasonic observables, atmospheric specifications, and interactions between atmosphere and ocean.