Numerical Simulation of Sudden Stratospheric Warmings.
NAVAL RESEARCH LAB WASHINGTON DC
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A mechanistic, quasigeostrophic model with a self consistent calculation of the mean zonal flow was used to numerically simulate sudden stratospheric warmings generated by a single zonal harmonic m planetary wave. The development of a warming depends critically on the two factors which govern the transmission of planetary waves to the upper stratosphere 1 the strength of the westerly winds in the lower stratosphere and 2 the magnitude of wave damping in the same region. Major warmings can only develop when the prewarming lower stratospheric winds are strong. Damping controls the maximum amplitude that a warming can attain and the time constant for its growth rate. Long term integrations with a steady forced m 1 wave show that the mean flow evolves to a steady, asymptotic state with net cooling in the polar mesosphere from planetary waves. But steady m 2 forcing leads to multiple generation of warmings which are similar to stratospheric vacillations.