Abstract
Abstract. Many gravity wave analyses, based on either observations or model simulations, assume the presence of only a single dominant wave. This paper shows that there are much more complex cases with gravity waves from multiple sources crossing each others' paths. 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 of around 400 km could be characterised using a 3-D wave-decomposition method. The smaller-scale wave components with horizontal wavelengths below 200 km were discussed by visual inspection. 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 are found to propagate 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. Despite their coarser vertical resolution compared to GLORIA measurements, co-located AIRS measurements in the middle stratosphere are in good agreement with the ray tracing and ERA5 results, proving once more the validity of simple ray-tracing models. Thus, this paper demonstrates that the high-resolution GLORIA observations in combination with simple ray-tracing calculations can provide an important source of information for enhancing our understanding of gravity wave propagation.
Highlights
Gravity waves (GWs) are an important coupling mechanism in the atmosphere as they can transport energy and momentum over large horizontal and vertical distances. Even though they were discovered in the first half of the 20th century (Wegener, 1906; Trey, 1919), many processes regarding their sources, propagation, and dissipation are still not fully understood (Alexander et al, 2010; Geller et al, 2013; Plougonven and Zhang, 2014). Due to this lack of understanding and because of computational constraints, gravity waves are oversimplified in current numerical weather prediction and climate projection models by employing parameterisation schemes
The GLORIA retrievals for both flight legs show a prominent wave structure with ≈ 400 km horizontal and ≈ 6–7 km vertical wavelength
A complex gravity wave field above southern Scandinavia was examined with respect to its sources and propagation paths
Summary
Gravity waves (GWs) are an important coupling mechanism in the atmosphere as they can transport energy and momentum over large horizontal and vertical distances Even though they were discovered in the first half of the 20th century (Wegener, 1906; Trey, 1919), many processes regarding their sources, propagation, and dissipation are still not fully understood (Alexander et al, 2010; Geller et al, 2013; Plougonven and Zhang, 2014). Due to this lack of understanding and because of computational constraints, gravity waves are oversimplified in current numerical weather prediction and climate projection models by employing parameterisation schemes. Krisch et al.: Interaction of gravity waves with different source mechanisms the surface temperature, surface pressure, and middle atmosphere circulation characteristics (Sigmond and Scinocca, 2010; McLandress et al, 2012; Shepherd, 2014; Sandu et al, 2016; Garcia et al, 2017)
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