Troposphere-Stratosphere Coupling Processes

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Transfer of momentum, energy, and trace constituents between the troposphere and the stratosphere is crucial for determining the dynamical and chemical climatology of the stratosphere, and is also of significance for the upper troposphere. The momentum balance in the stratosphere is sensitive to momentum transfer across the tropopause by vertically propagating gravity waves ranging from planetary scale to small-scale. Chemical processes crucial to the stratospheric ozone balance depend on the transfer of trace constituents across the tropopause. Thus, the understanding of the troposphere-stratosphere coupling is essential for understanding the global circulation of the stratosphere, the chemistry of the ozone layer, and the chemistry and climate of the upper troposphere. Moreover, the influence of the vertically propagating gravity waves extends well into the mesosphere where they are a major factor in the zonal forcing of the circulation as well as a source for the generation of smaller scale secondary waves. Convective storms and squall lines are significant sources for the generation of vertically propagating gravity waves. In their previous work, the PIs used a two-dimensional model to study the momentum transfer. Under this award, they will extend much of that work to three dimensions, both in the stratosphere and mesosphere, examining the effects on the large-scale circulations. In addition, the PIs will study tracer transport using their three-dimensional cloud model. An additional topic that is not an extension of previous work is the study of the stratospheric transport circulation and its relation to the so-called "Arctic Oscillation". The PIs will explore the similarity between topographically-forced planetary waves and the observed Arctic Oscillation and the relationship to the stratospheric circulation.