Analysis of Large-scale Atmospheric Gravity Waves as observed in Keograms of OH-Airglow Images

Kurzfassung

Several airglow cameras called FAIM (Fast Airglow IMager) are used by the German Remote Sensing Data Centre and the University of Augsburg to observe atmospheric gravity waves in OH airglow. OH airglow is a light emission due to chemical reactions in the upper-meosphere lower thermosphere region (UMLT). It can be used as a tracer to observe and characterise gravity waves in this altitude. In this work, keograms (time verses latitude/longitude graphs created from individual images captured during the night) are used to analyse the gravity wave parameters. A Fast Fourier Transform is applied on the keograms and the wave parameters are determined this way. A clear seasonal dependency is found in the horizontal propagation direction of the gravity waves. Periods of the analysed gravity waves mainly range from 5 min to 1.5 hours. It is shown that the keogram analysis allows investigating gravity waves that exceed the field-of-view of the camera system and thus overcomes this limitation.