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The Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) is an airborne infrared limb imager that can measure temperature and trace gas concentration data in the Upper Troposphere and Lower Stratosphere (UTLS) with high vertical resolution (up to 200 m). In addition to standard 1-D retrievals, a unique 3-D data set can be obtained by flying around the observed air mass and performing a tomographic retrieval. Tomography presents a challenging inverse modelling problem that typically requires an introduction of some general knowledge of the atmosphere (regularisation) due to its underdetermined nature. In this thesis, a consistent, physically motivated (no ad-hoc parameters) regularisation scheme based on spatial derivatives of first order and Laplacian is introduced. As shown by a case study with synthetic data, this scheme, combined with newly developed irregular grid retrieval methods, improves both upon the quality and the computational cost of 3D tomography. The new methods were used to analyse data from the WAVE Driven Isentropic Exchange (WISE) measurement campaign in 2017. A Rossby wave breaking event was observed with the GLORIA instrument during two research flights two days apart. The tomographic retrieval revealed complex vertical structures in stratospheric tracers (ozone and nitric acid) with multiple vertically stacked filaments related to several previous Rossby wave breaking events. With the help of backward trajectory calculations, much the observed tracer structure could be understood as stirring and mixing of air masses of tropospheric and stratospheric origins. Enhanced mixing between stratospheric and tropospheric air near the polar jet with some transport of water vapour into stratosphere was observed. In the late stage of the RW breaking event, air masses seen in the first flight were stretched to very thin filament containing air rich in stratospheric tracers and showing signatures of mixing.