Data Processing and Trace Gas Retrievals for the GLORIA Limb Sounder

The chemical composition of the Upper Troposphere and Lower Stratosphere (UTLS) region and the dynamical processes occurring within it have a particularly strong effect on radiative forcing, and hence surface climate. A lack of quantitative understanding of the region around the tropopause, and especially of exchange of trace constituents between the stratosphere and the troposphere, severely limits the predictive capabilities of current climate models. More and spatially better resolved observations are needed in order to close this gap. To this end, the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) was developed in a collaboration between the German research centres Forschungszentrum Jülich GmbH and Karlsruher Institut für Technologie. GLORIA is the descendant of the highly successful MIPAS and CRISTA instruments and has been designed with both chemical and dynamical analysis of the UTLS in mind. The imaging technology utilised by GLORIA and the resulting high data rate present unprecedented opportunities for data analysis, but also challenges for the processing of the recorded measurements. In this work, a new integrated data processing system designed for GLORIA is presented, as well as novel techniques for calibration and diagnosis. As an application of the new data processing chain, a polar flight from the combined TACTS/ESMVal campaign is presented which was performed on September 23rd, 2012, along a trajectory mostly above the Scandinavian peninsula. A selection of measurements from this flight is processed into calibrated spectra and then analysed further using the JURASSIC2 retrieval processor. Retrieved cross-sections of ozone, nitric acid, water vapour and atmospheric temperature are shown and compared with calculations from the Chemical Lagrangian Model of the Stratosphere (CLaMS), as well as potential vorticity from the European Centre for Medium-Range Weather Forecasts (ECMWF). The measurements reveal a highly inhomogeneous UTLS region suggesting that tropospheric air masses have been transported into the polar stratosphere, which is also indicated by the ECMWF data and further supported by CLaMS trajectory calculations. Two main structures can be identified. One is an anticyclone resulting from a mid-latitude wave-breaking event that transported tropospheric air into the observed region. The other is a vertically confined cyclone of seemingly stratospheric origin. The results are a successful application of both the newly-developed processing chain as well as the GLORIA instrument itself and highlights GLORIA’s ability to observe the effect of dynamic and transport processes in the UTLS