LIM: Forschung: Gravity wave coupling processes and their decadal variation

FORSCHUNG

GW-CODE: Gravity wave coupling processes and their decadal variation
(DFG JA 836/21-1, 2005-2007)

Solar energy is deposited at various heights of the Earth’s atmosphere via different processes. To identify whether solar influence is caused in-situ or imposed from another altitude region physical and quantitative understanding of the coupling processes between different atmospheric layers is essential.

One major coupling process is dynamical coupling by gravity waves (GWs). Some fundamental questions still to be answered are the relative contribution of different wave source mechanisms and their spatial and temporal variations as well as the absolute strength of GW momentum flux. GWs in global climate models (GCMs) are implemented by parameterizations using simplifications as e.g. immediate and merely vertical propagation of GWs.

In GW-CODE long-term data sets of GW variance will be generated to study seasonal and multiennial variations. These data will also be compared to global GW modeling employing the Warner and McIntyre spectral model. Measurement-optimized GW parameterizations will be used in the COMMA-LIM model to study the interactions of GWs, mean circulation, and planetary waves.

Project-related publications

The figure presents a 20-year mean time-height cross-section of zonal wind variance in the 0.7 - 3 h period window measured over Collm. Isolines show background zonal wind. Clearly visible is a seasonal cycle with summer maximum in the mesosphere, connected with maximum mean wind shear there.

The figure shows time series of seasonal mean gravity wave activity at 91 km over Collm. for Spring, Summer, and Autumn 20, 40 and 60 m2/s2 are added. Clearly visible is stronger activity during solar maximum conditions, probably connected with circulation changes in the mesosphere.

The project is part of the DFG priority program "CAWSES". The project bases on a collaboration with

Project coordinator is M. Ern, IGC-1, FZ Jülich