Contribution of Infrasound Monitoring for a Global Study of Winds and Gravity Waves in the upper atmosphere

The analysis of the infrasound data of the International Monitoring System, used for the verification of the Comprehensive Test Ban Treaty, shows that the infrasound detection and localisation are strongly submitted to the stratospheric and mesospheric winds, which influence the propagation of infrasound waves when they propagate in the acoustic channel formed by the temperature and wind gradients in the atmosphere. Propagation modeling based on existing semi-empirical atmospheric models roughly explains seasonal changes in infrasonic observables, but underestimates their fluctuations. This is due to the lack of precision in available upper wind models. Continuous infrasound monitoring of active volcanoes and ocean swell is proposed as a remote sensing method to provide a more accurate description of the wind fields in the stratosphere and mesosphere. The network provides also information about the high frequency component of gravity waves. These waves propagate in the middle atmosphere and impact the entire global circulation. Global monitoring of infrasound could greatly enhances our understanding of the dynamics of the upper atmosphere in a region where routine measurements still remain illusive.