1. The Temporal Morphology of Infrasound Propagation Douglas P. Drob 1, Milton Garces 2, Michael Hedlin 3, and Nicolas Brachet 4 1)Space Science Division, Naval Research Laboratory, Washington, DC 2)Infrasound Laboratory, University of Hawaii, Kona 3)Laboratory for Atmospheric Acoustics, University of California, San Diego 4)International Data Center, Provisional Technical Secretariat, CTBTO, Vienna Austria

2. Why are precomputed monthly average travel time tables poor for operational infrasound source location calculations? Expert knowledge suggests that the performance of automated infrasound event association and source location algorithms will be greatly improved by the ability to continual update station travel time curves to properly account for the seasonal/daily/hourly changes of the atmospheric state. - thus - Advocate for, develop, and integrate this capability into automated source location operations to reduced false alarm rates and improved network detection capability.

3. Requirements Knowledge of the atmospheric state. Procedures for calculating infrasound propagation characteristics. Procedures for utilization of travel time curves in automated event association and location algorithms. Validation. Systems integration.

4. Knowledge of the Atmospheric State HWM-93 –empirical climatology –data sparse –low resolution –global –time dependent –0 to 500 km Numerical weather prediction –operational –data rich –high-resolution –global/regional –4x daily –0 to 55/85 km NOAA-GSF, ECMWF, NASA-GEOS5, NOGAPS.

5. Hybrid Ground-to-Space Model Seamless global specification - U, V, T,  and P. Operational prototype, 4x daily from September 2002 to current, plus specific events to 1990.

7. Methodology 4x daily empirical climatologic and G2S atmospheric specifications from September 13, 2002 to April 31, 2007. Tau-P infrasound propagation characteristics (Garces et al., 1998). Calculate celerity, azimuth deviation, and turning height for all azimuths up to 35 ° elevation. Calculated from the network receiver perspective.

9. I56US Mid-latitude January 1, 2006 0:00 UT

10. Sound Velocity (m/s)Wind Velocity (m/s) Altitude (km) Zonal Meridional

18. Sound Velocity (m/s)Wind Velocity (m/s) Altitude (km) Zonal Meridional

23. Azimuth Deviation (degrees)

25. I55US Polar Latitude

27. Sound Velocity (m/s)Wind Velocity (m/s) Altitude (km) Zonal Meridional

32. Azimuth Deviation (degrees)

34. Conclusions Over the past 5 years we have developed and compiled reasonably good knowledge of the atmospheric state for infrasound propagation calculations. We have also developed and exercised robust procedures for calculating local infrasound propagation characteristics. Precomputed monthly average travel time tables and climatology are poor for operational infrasound source location calculations - performance of automated infrasound event association and source location algorithms will be greatly improved by the ability to continual update station travel time curves to properly account for the seasonal/daily/hourly changes of the atmospheric state

35. Challenges Integration of propagation code/travel times results into automated event association algorithms. Data volume and computational resource. Validation, Validation, Validation