Marine De Carlo

Sujet de thèse: Atmospheric infrasound generated by ocean waves: modelling of microbaroms at global scales and comparison wih International Monitoring System measurements

Advisors:  Alexis Le Pichon (CEA/DAM) & Fabrice Ardhuin (LOPS)

Funding : CEA

Summary:  Infrasound signals are continuously detected by the International Monitoring System (IMS) network. Between 0.1 and 0.6 Hz, coherent signals originating from the ocean, known as microbaroms, dominate the recorded signals. This thesis aims at better characterizing these sources of coherent noise for discrimination purpose in the framework of the Comprehensive nuclear Test Ban Treaty. Different theoretical microbarom models had been previously developed based on second-order
non-linear interactions of ocean waves. While early theories considered an infinite ocean depth and a source radiation depending on the acoustic wave elevation angle, other works have found a significant effect of the water depth by considering a monopolar radiation. This thesis extends these models by combining the effects of both finite depth and source directivity. The new source model predicts that the water depth has a negligible effect for the near-horizontally propagating acoustic waves that domi-
nate the recorded microbarom signals. A global model of microbaroms arrivals at ground stations is set up including ocean wave models, source models and atmospheric attenuation effects. A quantitative validation is performed by comparing modelling results with microbaroms detected by the IMS infrasound network over seven years. This thesis demonstrates that the new source model performs better than previous ones, and that the predictions are further enhanced by using wind-dependent attenua-
tion and an ocean wave model including coastal reflection. Beyond operational monitoring objectives, this work offers new perspectives to globally and continuously characterize infrasound propagation effect in the middle atmosphere.

My thesis work involved different parts:

  • Theory: how ocean wind-waves radiate acoustic waves in the atmosphere
  • Numerical modelling: propagation and attenuation of the microbarom sources
  • Data processing: finding the right way to compare detected microbarom signals with the numerical simulation of the directional microbarom spectrum


Hupe, P., Ceranna, L., Pilger, C., de Carlo, M., Le Pichon, A., Kaifler, B., & Rapp, M. (2018). Assessing middle atmosphere weather models using infrasound detections from microbaroms. Geophysical Journal International, 216(3), 1761–1767. doi:10.1093/gji/ggy520

De Carlo, M., Ardhuin, F., & Le Pichon, A. (2020). Atmospheric infrasound generation by ocean waves in finite depth: unified theory and application to radiation patterns. Geophysical Journal International. doi:10.1093/gji/ggaa015 ,