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Impact of infrasound on temperature variations in the upper Mesosphere / lower Thermosphere altitude region. C. Pilger and M. Bittner German Aerospace Center (DLR-DFD), Wessling, Germany ITW 2007, Tokyo, Japan. Outline. Introduction OH*-measurements with the GRIPS spectrometers

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  1. Impact of infrasound on temperature variations in the upper Mesosphere / lower Thermosphere altitude region C. Pilger and M. BittnerGerman Aerospace Center (DLR-DFD), Wessling, GermanyITW 2007, Tokyo, Japan

  2. Outline • Introduction • OH*-measurements with the GRIPS spectrometers • Infrasound (propagation) modeling • Temperature variations in the MLT - region • Summary

  3. Introduction Sources of Infrasound: Airglow - Intensity Aurora, … FOV AIRGLOW Meteoroids, … Earthquakes, Volcanoes, … IR-Emission Temperature - Variation Propagation Paths Surface Instruments (IR-Spectrometers)

  4. Airglow Limb view on the airglow layer as seen by the US spacecraft Clementine (false colour image, courtesy of U.S. Naval Research Laboratory)

  5. intensity, rel. units wavelength, nm monochromator mirror details e.g. in Bittner, M. et al., JASTP 2002 Ge-detector baffle Instrumentation GRIPS (Ground-based Infrared P-branch Spectrometer)

  6. A typical OH* - temperature measurement with high temporal resolution (45 sec): instrument: IR-spectrometer GRIPS 4 location: environmental research station Schnee-fernerhaus, Mt. Zugspitze time: 14 Dec 2006, 17:05-18:19 UT Temperature [K] 0 15 30 45 60 75 Time [min] Measurements: Temperature Time Series Measurements performed by Schmidt, C. (DLR-DFD)

  7. Wavelet analysis of the temperature time series: peaks with periods in the infrasound range (<5 min) can be seen Further investigation needed 15.0 4.5 12.0 4.0 9.0 3.5 Period [min] Intensity [rel. units] 3.0 6.0 2.5 3.0 2.0 1.5 0.0 0 15 30 45 60 75 Time [min] Analysis: Small scale structures (infrasound)

  8. Propagation Modeling by Ray Tracing (HARPA) INPUT OUTPUT Temperature (NRL-MSISE 00) Ray Paths (Range, Azimuth, Elevation) Horizontal Wind (HWM 93) Temperature Modeling Attenuation (Sutherland Bass 2004) Temperature Fluctuations MODELING Modeling Structure

  9. Zonal wind (eastward), m/s Model Input (Temperature, Wind) using MSIS-00 (for temperature) (Mass Spectrometer and Incoherent Scatter radar) and HWM-93 (for wind) models (Horizontal Wind Model) Temperature, K Picone, J.M. et al., JGR 2002 Hedin, A.E. et al., JATP, 1996

  10. Considered processes of attenuation: Classical loss (viscosity, conductivity) Diffusion loss Relaxation loss (rotational, vibrational) Model Input (Attenuation) Sutherland, L.C., H.E. Bass, JASA 2004

  11. Propagation Modeling using HARPA (Hamiltonian Ray-tracing Program for Acoustic waves in the atmosphere) Calculating propagation (by Hamilton Equations) and attenuation: • for a 0.5 Hz signal • cylindric spreading Hamilton Equations: Jones, R.M. et al. NOAA, 1986

  12. Considered processes for the development of a temperature fluctuation: Geometric spreading loss Amplification with decreasing background pressure Atmospheric attenuation loss O2 OH* Temperature Modeling Elevation Angle 10 deg. 50 deg. 90 deg.

  13. Temperature, K Temperature Fluctuations Calculating temperature fluctuations for: • a 100 Pa source signal • attenuation with 1 Hz frequency • cylindric spreading

  14. Summary Measurements: • Recording of OH*-airglow emissions (O2-airglow is in preparation) • Derivation of OH*-temperature fluctuations in the infrasound frequency region Modeling: • Use of climatological atmospheric background conditions • HWM 93, NRL-MSISE 00 • Description of infrasound propagation and attenuation • HARPA, Sutherland Bass 04 • Quantification of expected mesopause temperature variations

  15. Outlook Measurements: • Improvement of instrumental characteristics • temporal resolution and precision Modeling: • Implementation of realistic atmospheric background conditions • meteorological forecasts using e.g. the GME-model (DWD Global Model Earth) • Sensitivity of infrasound propagation with respect to disturbances • Development of a pattern recognition algorithm • discrimination of different infrasound sources

  16. Literature • BITTNER, M., OFFERMANN, D., GRAEF, H.H., DONNER, M. and HAMILTON, K., 2002. An 18-year time series of OH rotational temperatures and middle atmosphere decadal variations. Journal of Atmospheric and Solar-Terrestrial Physics 64, 1147-1166. • HEDIN, A.E., FLEMING, E.L., MANSON, A.H., SCHMIDLIN, F.J., AVERY, S.K., CLARK, R.R., FRANKE, S.J., FRASER, G.J., TSUDA, T., VIAL, F. and VINCENT, R.A., 1996. HWM - Empirical wind model for the upper, middle and lower atmosphere. Journal of Atmospheric and Terrestrial Physics 58, 1421-1447. • JONES, R.M., RILEY, J.P. and GEORGES, T.M., 1986. HARPA – A versatile three-dimensional Hamiltonian ray-tracing program for acoustic waves in the atmosphere above irregular terrain. NOAA Special Report, http://cires.colorado.edu/~mjones/raytracing. • PICONE, J.M., HEDIN, A.E., DROB, D.P. and AIKIN, A.C., 2002. NRLMSISE-00 - Empirical model of the atmosphere: Statistical comparisons and scientific issues. Journal of Geophysical Research 107, 1468, doi: 10.1029/2002JA009430. • SUTHERLAND, L.C. and BASS, H.E., 2004. Atmospheric absorption in the atmosphere up to 160 km. Journal of the Acoustic Society of America 115 (3), 1012-1032, doi: 10.1121/1.1631937. Thank you

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