Airglow observations of orographic, volcanic and meteorological infrasound signatures

Infrasound is generated by several different natural hazards as, e.g., volcanic eruptions and severe weather, but also due to orography (flow over mountains) or anthropogenic sources (e.g. explosions). It propagates from the surface to the middle and upper atmosphere, is characterized by pressure and temperature fluctuations on its path and is reflected back to the ground in so-called ducts. The effects of infrasound in terms of temperature fluctuations in the middle atmosphere, especially in the mesopause altitude region (80-100 km), can be observed using ground-based airglow spectrometers as, e.g., the GRIPS (GRound-based Infrared P-branch Spectrometers) instruments of the German Aerospace Center (DLR). A method to identify and spectrally analyse infrasound signatures in mesopause temperature time series derived from nocturnal GRIPS airglow observations is presented. The automatic identification of spectral features in the observations and association to distinct infrasound sources is described. Source verification is performed by considering weather situations, volcanic activity and infrasound propagation modelling. The results in terms of identified infrasound sources of orographic, volcanic and meteorological origin are presented and discussed for a number of different case studies. (C) 2013 Elsevier Ltd. All rights reserved.