12th Conference on Middle Atmosphere

Tuesday, 5 November 2002
Gravity wave/large-scale flow interaction: a comparison of observation and model prediction
Redina L. Herman, University of Illinois, Urbana, IL; and W. A. Robinson and S. J. Franke
Medium frequency (MF) radar data from Urbana, IL (40 10 10 N, 88 09 36 W) have been used to detect signatures of gravity wave/large scale flow interactions in the mesosphere. We focus on the interaction between gravity waves and two large-scale flow features: quasi-two day wave (a periodic feature) events and sudden stratospheric warming (a non-periodic feature) events. For a periodic background wind modulation we obtain a periodic gravity wave modulation and for a non-periodic background wind modulation we obtain a non-periodic gravity wave modulation. Once the interaction signature is detected we then use simple gravity wave parameterizations to try to simulate it. The gravity wave parameterizations used in this study include critical level filtering, the widely used Lindzen/Holton linear saturation theory, and some flavors of diffusive filtering. Data from the United Kingdom Meteorological Office (UKMO) Reanalysis are used to provide the stratospheric wind fields through which the gravity waves propagate.

Observational evidence of gravity wave/large scale flow interaction signatures will be presented. A comparison of the parameterization-simulated gravity wave interaction signatures for the different gravity wave parameterizations will also be presented. These parameterization-simulated interaction signatures will then be compared to the observed gravity wave/large scale flow interaction signatures.

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