12th Conference on Middle Atmosphere

Tuesday, 5 November 2002
Gravity wave forcing in the stratosphere: Observationalconstraints from UARS
M. Joan Alexander, NorthWest Research Associates, Boulder, CO; and K. H. Rosenlof
Gravity wave forcing in the stratosphere slows the winter jet stream winds, accelerates the onset of the summer westward winds, helps to drive the global mean-meridional transport circulation, and helps to drive the equatorial quasibiennial and semiannual oscillations in zonal winds. The effect of gravity waves in these processes is quantified using stratospheric wave forcing derived from UARS observations. These effects are inadequately handled in global circulation models without parameterizations of gravity wave effects that require details about the gravity wave properties as input. In this study, a simple linear model of gravity wave propagation and dissipation is applied to observed wind and stability fields to study the sensitivity of modeled gravity wave effects to the input properties of the gravity wave spectrum. A wide parameter space describing gravity wave properties at the tropopause is sampled, and the stratospheric gravity wave forcing effects are correlated with those derived from the observations. The comparison reveals whether or not modeled gravity wave forcing effects can be used to constrain the input wave properties at the tropopause as has been attempted in numerous global model studies. In some cases, the solutions are shown to be very non-unique so that the gravity wave input properties cannot be easily derived in this way. In other cases, the gravity wave effects constrain the input wave properties much more effectively. The results suggest important latitudinal variations in the properties of gravity waves that affect the stratosphere.

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