Multi-Scale Dynamics of Gravity Waves (MS-GWaves)
Confidence in climate prediction can only be gained if the present climate is modeled correct-ly for the correct reasons. Currently, there is a debate on dynamical features such as the predicted enhancement of the Brewer-Dobson circulation, the dynamical downward coupling of the stratosphere on the troposphere, and ozone super-recovery. A particularly large source of uncertainty in this context are internal gravity waves (GWs), which cannot be re-solved by current chemistry-climate models and are represented by largely oversimplified parameterizations instead. The research unit (RU) will formulate explicit models of GW exci-tation, propagation, and dissipation in a physically and mathematically consistent way. These will be tested via process-resolving numerical modeling and measurements. Special attention will be given to multi-scale interactions of gravity waves with turbulence, with the balanced flow, and of unresolved small-scale GWs with large-scale, resolved GWs. Models to be de-veloped will lead to a unified parameterization of GWs, from their sources to their dissipation. Both the GW parameterization and global GW permitting and local GW resolving modeling will be used to quantify and mitigate the uncertainties in the understanding of GW impacts on the atmospheric circulation, large-scale dynamical processes in the atmosphere, and climate change. The effort will be based on a close interdisciplinary interaction of mathematics, theo-ry, high-resolution numerical modeling, and measurements of both the wave processes themselves and their effects on the global scale. This combination of methods is employed since only measurements hold the direct link to reality, only theory allows to understand, and since only high-resolution modeling can provide a detailed diagnosis. Such a comprehensive program is far beyond the possibility of a single research institute or some bilateral coopera-tion but requires a RU with various institutes joining their experimental, computational, and theoretical capabilities. The long-term gains from the RU are to be: - An enhanced and deepened overview of the spatial, temporal and spectral distribution of GWs in the atmosphere. - A significantly improved understanding of the processes causing and controlling the corre-sponding GW dynamics. - Based on this an increase in the robustness and completeness of the parameterization of GWs as subgrid-scale phenomenon, addressing source processes, GW propagation, GW mean-flow interaction, and GW dissipation. - Hence a more reliable performance of GW parameterizations under anomalous conditions, e.g. climate change.