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 2 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Outline Introduction OH*-measurements with the GRIPS spectrometers Infrasound (propagation) modeling Temperature variations in the MLT - region Summary 3 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Introduction AIRGLOW Instruments (IR-Spectrometers) Aurora, Meteoroids, Earthquakes, Volcanoes, IR-Emission Sources of Infrasound: FOV Surface Propagation Paths Airglow - Intensity Temperature - Variation 4 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio 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 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Bittner, M. et al., JASTP 2002 details e.g. in Ge-detector monochromator baffle mirror Instrumentation GRIPS (Ground-based Infrared P-branch Spectrometer) wavelength, nm intensity, rel. units 6 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Measurements: Temperature Time Series Measurements performed by Schmidt, C. (DLR-DFD) 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] Time [min] 0 7 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Analysis: Small scale structures (infrasound) Intensity [rel. units] Period [min] Time [min] Wavelet analysis of the temperature time series: peaks with periods in the infrasound range ( C. Pilger and M. Bittner > ITW 2007, Tokio Modeling Structure Temperature (NRL-MSISE 00) Horizontal Wind (HWM 93) Attenuation (Sutherland Bass 2004) INPUT Propagation Modeling by Ray Tracing (HARPA) Propagation Modeling by Ray Tracing (HARPA) Temperature Modeling Temperature Modeling MODELING OUTPUT Ray Paths (Range, Azimuth, Elevation ) Ray Paths (Range, Azimuth, Elevation ) Temperature Fluctuations Temperature Fluctuations 9 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Model Input (Temperature, Wind) using MSIS-00 (for temperature) (Mass Spectrometer and Incoherent Scatter radar) and HWM-93 (for wind) models (Horizontal Wind Model) Zonal wind (eastward), m/s Temperature, K Picone, J.M. et al., JGR 2002 Hedin, A.E. et al., JATP, 1996 10 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Model Input (Attenuation) Considered processes of attenuation: Classical loss (viscosity, conductivity) Diffusion loss Relaxation loss (rotational, vibrational) Sutherland, L.C., H.E. Bass, JASA 2004 11 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Jones, R.M. et al. NOAA, 1986 Propagation Modeling using HARPA (Hamiltonian Ray-tracing Program for Acoustic waves in the atmosphere) Hamilton Equations: Calculating propagation (by Hamilton Equations) and attenuation: for a 0.5 Hz signal cylindric spreading 12 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Temperature Modeling Considered processes for the development of a temperature fluctuation: Geometric spreading loss Amplification with decreasing background pressure Atmospheric attenuation loss 10 deg.90 deg.50 deg. Elevation Angle O2O2 OH* 13 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Temperature Fluctuations Temperature, K Calculating temperature fluctuations for: a 100 Pa source signal attenuation with 1 Hz frequency cylindric spreading 14 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Summary Measurements: Recording of OH*-airglow emissions (O 2 -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 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio 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 Impact of infrasound on temperature variations in the MLT region > C. Pilger and M. Bittner > ITW 2007, Tokio Literature BITTNER, M., OFFERMANN, D., GRAEF, H.H., DONNER, M. and HAMILTON, K., An 18-year time series of OH rotational temperatures and middle atmosphere decadal variations. Journal of Atmospheric and Solar-Terrestrial Physics 64, 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., HWM - Empirical wind model for the upper, middle and lower atmosphere. Journal of Atmospheric and Terrestrial Physics 58, JONES, R.M., RILEY, J.P. and GEORGES, T.M., HARPA A versatile three-dimensional Hamiltonian ray-tracing program for acoustic waves in the atmosphere above irregular terrain. NOAA Special Report,PICONE, J.M., HEDIN, A.E., DROB, D.P. and AIKIN, A.C., NRLMSISE-00 - Empirical model of the atmosphere: Statistical comparisons and scientific issues. Journal of Geophysical Research 107, 1468, doi: /2002JA SUTHERLAND, L.C. and BASS, H.E., Atmospheric absorption in the atmosphere up to 160 km. Journal of the Acoustic Society of America 115 (3), , doi: / Thank you