High resolution simulation of observed cases of stratospheric gravity wave breakdown

We are conducting numerical simulations of air flow over realistically patterned Rocky mountains. For the observed atmospheric flow profiles used, the gravity waves produced propagate upward into stratospheric altitudes where they amplify and undergo wavebreaking. Vortex patterns are produced in patches superimposed on the wave pattern. Location of these patches within the wave compare well with data from aircraft observations. Currently, size scales of .3 to 1 km are resolvable, and inlay simulations can resolve features as small as 30 meters. The vortices appear in layers of wavebreaking and have an axis parallel to the ground and perpendicular to the flow.

The stratospheric vortex train first appears downstream of the mountain ridge and then propagates upstream. After onset, successively smaller features are produced in the vortex layer. This layer is superimposed on a still recognizable wave pattern. The intensities of wave and vortex tend to oscillate out of phase. Perturbation velocity is examined for several vortices. One particu larily strong vortex encountered produced speeds near 30m/s (100 feet per second). These results have significance for stratospheric mixing and aviation.