Das Projekt "Die Auswirkung von Gravitationswellen auf das Klima" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Meteorologie durchgeführt. General Information/Objectives: This project aims to advance our understanding and process modelling of gravity waves in the atmosphere, and to improve the quality of gravity wave parametrizations for general circulation models of the atmosphere. Brief Description of the Research Project: The project is a combined effort by researchers with expertise in the observation of gravity waves, in global circulation models (GCMs) of the atmosphere, in theoretical process and data studies of gravity wave behaviour, and in parametrization development. In order to improve our understanding of observed gravity wave spectra, and to help bridge the gap between observational data and gravity wave parametrizations for GCMs, a new, 'intermediate' level of process modelling, based on stochastic hypotheses, e.g. about spectral phase information, will be developed and compared with data. The resulting 'intermediate models' will, for the first time, incorporate both monochromatic (orographic) and broadband (nonorographic) waves in a way that allows for their mutual interaction. New and improved gravity wave parametrizations for GCMs that build on the above will be developed using an intermediate model as a test-bench in addition to direct comparisons with data. A programme of carefully controlled GCM experiments, in several GCMs, will test the most promising parametrization(s) together with the spectral parametrization proposed by Hines. An innovative top boundary condition for GCMs will be developed and tested. This exploits recently-clarified dynamical principles (relating to so-called 'downward control') to avoid the need to simulate the mesosphere while preserving to good approximation the mesospheric, gravity-wave-dominated contribution to the wave-driven pumping of chemical constituents including greenhouse gases. Prime Contractor: University of Cambridge, Department of Applied Mathematics and Theoretical Physics; Cambridge/UK.