Modeling Infrasound Propagation with Realistic Terrain and Atmospheres Using a Three-Dimensional Finite-Difference Time-Domain Method

Observations and numerical modeling have shown that infrasound propagation is strongly influenced by topography within approximately 10 km from the source. Recent analysis of regional distance (>10 km) infrasound and related computational efforts using axisymmetric finite-differences and the geometric acoustics approximation have shown that topographic influence extends over hundreds of km and is especially strong when considering propagation through the troposphere. This is in addition to the strong influence wind and temperature gradients have on propagation at these distances, suggesting that topography and 3-D atmospheric structure need to be accounted for in waveform modeling. Here we show preliminary results depicting linear acoustic propagation through a moving, inhomogeneous atmosphere using an in-development 3-D finite-difference time-domain (FDTD) propagation code. We compare infrasound propagation over flat ground and realistic terrain to identify 3-D effects not previously included in axisymmetric finite difference simulations and finite frequency effects not included in 3-D ray tracing analysis. We also compare our synthetic waveforms with existing community infrasound propagation codes and discuss future developments, including open source licensing for community use. Lastly, we present preliminary applications of this code to the Humming Roadrunner experiments and similar data sets.