During winter poleward breaking Rossby waves are locally associated with intense jet streams in the tropopause region. These jets may generate inertia-gravity waves (IGW) of about 900 km horizontal wavelength. Such IGWs may propagate horizontally and vertically and may play a siginificant role for the transport and mixing in the middle atmosphere.

In a case study the 5-th generation mesoscale model (MM5) is used to simulate the situation over Central Europe for 17 - 19 December 1999. During this time, a field campaign had been performed at Kuehlungsborn (54 °N, 12 °E) including 17 radiosondes and VHF radar oservations. The model was capable to reproduce the observed IGWs with a wavelength of 800 - 1000 km in the horizontal, 2 - 4 km in the vertical and an intrinsic period of 12 h.

A number of numerical experiments was run in order to relate different generation processes to different IGW patterns. For a run without orography, moisture and surface friction we found long IGWs too, which confirms the active role of the jet stream in the generation process. It is also shown, that shorter IGWs (about 300 km) are excited orographically and travel through the stratosphere. The contribution of both forcing processes to vertical energy and momentum transport is discussed.