Superposition of gravity waves with different propagation characteristics observed by airborne and space-borne infrared sounders

Abstract. A complex gravity wave structure consisting of a superposition of multiple wave packets was observed above southern Scandinavia on 28 January 2016 with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA). The tomographic measurement capability of GLORIA enabled a detailed 3-D reconstruction of the gravity wave field and the identification of multiple wave packets with different horizontal and vertical scales. The larger-scale gravity waves with horizontal wavelengths 5 around 400 km could be characterised using a 3-D wave-decomposition method. For the characterization of the smaller-scale wave components with horizontal wavelengths below 200 km, the 3-D wave-decomposition method needs to be further improved in the future. For the larger-scale gravity wave components, a combination of gravity-wave ray-tracing calculations and ERA5 reanalysis fields identified orography as well as a jet-exit region and a low pressure system as possible sources. All gravity waves propagate 10 upward into the middle stratosphere, but only the orographic waves stay directly above their source. The comparison with ERA5 also shows that ray-tracing provides reasonable results even for such complex cases with multiple overlapping wave packets. AIRS measurements in the middle stratosphere support these findings, even though their coarse vertical resolution barely resolves the observed wave structure in this case study. The high-resolution GLORIA observations are therefore an important source of information on gravity wave characteristics in the upper troposphere and lower stratosphere region.