Non-stationary Gravity Wave retrievals for GLORIA

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Gravity waves (GWs) are an essential driver of global circulation patterns in the stratosphere and mesosphere. Frequently discussed are GWs excited by jets and fronts or GWs excited by flow over orography. In idealized model studies it is easy to separate the two different sources, but for observed waves this is more difficult.We propose to observe GWs with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the SouthTRAC campaign, perform retrievals confined by GW physics with a simple spectral GW model, separate different wave packets by different phase speeds and investigate the origin of these waves via ray-tracing methods.In detail, this will involve the following steps:In order to study GWs in the upper troposphere and lower stratosphere, we perform GW targeted research flights with GLORIA deployed in the belly pod of HALO. We derive 3-D distributions of atmospheric temperatures and trace species from the measured radiances by means of inverse modeling.Due to the time needed to acquire tomographic measurements, at the moment this requires the temperature field to be nearly stationary.To overcome this limitation and investigate non-stationary GWs, we will extend the inversion by including a spectral GW model in the forward model. The aim is a direct gravity wave parameter retrieval.By using the built-in gravity wave model to simulate the vertical propagation of the assumed waves, we achieve a drastic reduction of the state vector and thus a more stable retrieval. This reduction will allow us to include also non-zero ground-based frequencies in the state vector.From the results, 3D temperature fields can be reconstructed for different synoptic time steps.The spectral representation of the GWs inferred in the retrieval can be utilized to separate different phase speeds associated with different sources. The technique can be applied to superpose different waves in the same altitude and time-domain or in the same region. In the upcoming SouthTRAC campaign multi-instrument measurements of complex atmospheric situations will be acquired to observe GWs from different sources over a wide altitude range. This offers the opportunity to examine, how well these waves can be separated and, ideally, if and how these GWs interact.The PhD project consists of three major work packages to achieve this goal.First, the tomographic inversion method needs to be fully developed in cooperation with the mathematics department of the RWTH Aachen. Its capabilities and limitations will be thoroughly investigated using synthetic and model data. The second work package deals with taking active part in the measurement campaign.The third work package will use the newly developed tools to analyze the data acquired during SouthTRAC and gain physical insight into the observed GWs and their source processes.