Advancement of Infrasound Propagation Calculation Techniques Using Mesoscale Atmospheric and Terrain Specifications

Numerical calculation of infrasound propagation paths is necessary to support accurate infrasound event identification, phase association, and source location. Predicting the details of infrasound propagation relies both on propagation models that capture the fundamental physical processes and on characterization of the propagation medium, namely the global atmosphere from the ground to altitudes above 100 km. Therefore the accuracy of propagation modeling depends in part on the fidelity of the atmospheric characterization. Furthermore, for infrasound propagation at regional and local ranges, characterized by higher frequencies than propagation at global ranges, effects of the boundary conditions of the propagation domain, in particular the terrain elevation, become increasingly important. The analysis tool kit Infrasound Modeling of Atmospheric Propagation (InfraMAP) integrates infrasound propagation models and environmental representations, including synoptic updates of the atmospheric specification at low and middle altitude, such as the output from numerical weather prediction models that supplement climatological characterization of temperature, wind, and air composition at high altitude. The Naval Research Laboratory (NRL) Ground-to-Space (G2S) semi-empirical spectral model provides a global specification of the atmosphere that can be utilized in InfraMAP. These capabilities for propagation calculation and atmospheric specification allow infrasound researchers to investigate critical propagation phenomena, conduct sensitivity studies, and compare results of numerical modeling with observed signals. Recent efforts develop techniques for utilizing accurate, high-resolution regional atmospheric specifications and terrain elevation databases with infrasound propagation modeling codes. Mesoscale atmospheric models, which focus on the meteorology of a specific region, can account for and resolve important wind and temperature phenomena relevant to regional and local infrasound propagation. Such models can also provide atmospheric profiles that are consistent with the variable terrain elevation in a region. By investigating realistic atmospheric models and terrain specifications at a range of resolutions, we seek insight into the appropriate spatial and temporal scales that are necessary for achieving improved infrasound predictions at the relevant frequencies. Ground truth events are studied in order to assess performance of techniques for incorporating mesoscale atmospheric models and terrain specifications with propagation models and to evaluate the benefits for infrasound monitoring. 29th Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies