Christoph Pilger
Modellierung von Infraschall in der Atmosphäre: Auswirkungen auf die Mesopausentemperatur
Betreuer: Prof Dr. Michael Bittner [Experimentalphysik II]
Datum der mündlichen Prüfung: 13.12.2011
133 Seiten, deutsch
Infrasound is one of the dynamic wave processes with potential influence on the pressure and temperature profile of the atmosphere. Infrasound is generated by a variety of natural and artificial sources and can be used for remote sensing of the atmosphere and the detection of natural hazards and man-made signals. The propagation modelling of infrasound using ray-tracing methods with regard to a realistic background profile of the atmosphere is presented in this study. The effects of infrasound in terms of temperature fluctuations and heating rates are quantified and compared to time series of mesopause altitude temperatures observed by airglow spectroscopy. Different sources of infrasound may have an influence on the observed temperature profiles, therefore first steps for infrasound signal discrimination and pattern recognition are described in this work. The modelling of realistic atmospheric background conditions is found to have significant influence on the sound propagation. Especially atmospheric attenuation, but also wind and temperature variations modify a sound signal and may permit or prohibit the detection of a signal at a certain location. The quantification of infrasonic influences on middle atmosphere temperatures shows a generally weak influence of the sound waves, but nevertheless the potential for paticular sources of infrasound to be detected. Temperature fluctuations of strong singular sources or heating rates of strong continuous sources might be detectable using sufficient instrumentation with high temporal resolution and good precision. A discrimination of infrasonic signals regarding observable parameters in temperature time series is accomplished in this study. Signals are distinguished using their frequency, amplitude and waveform characteristics. Comparisons to observed data during 2 years of airglow measurements with different instruments show the presumable occurrence of (infrasonic) mountain-associated waves and meteorological sources as e.g. severe weather and thunderstorms.