Nuclear Treaties Branch

The analysis tool kit InfraMAP (Infrasonic Modeling of Atmospheric Propagation) consists of three infrasound propagation models (3-D ray trace, normal mode, and parabolic equation), two atmospheric characterizations (HWM and MSIS), a global topography database, and user interfaces for model execution and data visualization. Software features have been implemented that allow improvements in both fidelity and functionality over previously available infrasound modeling capabilities. The ability to predict propagation characteristics that affect localization is therefore enhanced. InfraMAP has been delivered to DTRA and is currently being utilized by CTBT researchers and analysts. Understanding variability in propagation paths is a necessary step in the development of an infrasound network performance model. InfraMAP includes a Propagation Variability module that uses a stochastic approach to assess variability in travel time and arrival azimuth. Environmental perturbation fields are defined using a 1-D vertical wave number spectrum of the horizontal wind. A Monte Carlo simulation is executed where rays are traced through multiple environmental realizations, consisting of the sum of mean and perturbed profiles. Ray parameters are calculated for each realization, and the sensitivity of ray tracing calculations to variability in wind profiles can be stochastically quantified. The modeled distributions of propagation variables can be used in assessing areas of uncertainty in source location. InfraMAP provides the infrastructure for incorporation of a localization capability as well as the existing propagation and variability modeling capabilities. Systematic sensitivity analyses have been conducted to understand the effect of temporal, spatial and environmental parameters on accurate modeling of long-range infrasound propagation. These sensitivity investigations, along with comparisons of model predictions with measured data, serve to identify specific areas where additional infrasound research and further development of modeling techniques are needed