| Integrations performed with 2-dimensional and 3-dimensional models of the stratosphere reveal that planetary wave activity strongly affects the strength of the Brewer-Dobson circulation during winter and the resulting distribution of long-lived stratospheric constituents such as ozone. Investigations of the mean-meridional circulation with a 2-dimensional isentropic model indicate that interaction between eddy advection and thermal dissipation produces large-scale subsidence inside the polar vortex. Displacements of the vortex cause air parcels to oscillate between differing radiative environments, preventing them from reaching radiative equilibrium. Irreversible heat transfer that stems from relaxation toward radiative equilibrium introduces a hysteresis into the thermodynamic state of air parcels, leading to a downward drift to lower isentropic surfaces.; Planetary wave forcing representative of northern winter climatology leads to a specific 3-dimensional structure to the Brewer-Dobson circulation in 3-dimensional model integrations. Realistic forcing displaces the polar vortex out of zonal symmetry, resulting in poleward transport of air over Siberia and equatorward transport over the North Atlantic. As in the 2-dimensional analysis, irreversible heat transfer introduces a hysteresis into the thermodynamic state of air orbiting the vortex. This leads to the systematic increase of total ozone reflecting the degree of local sinking motion and deflection of isentropic surfaces. Furthermore, the evolution of the calculated total ozone distribution mirrors that of TOMS total ozone.; Interannual variability in planetary wave forcing influences the interannual variability in wintertime total ozone at northern midlatitudes. Wintertime increases in total ozone depend strongly upon the upward flux of planetary wave activity propagating out of the troposphere. The combined influence of planetary wave forcing, the QBO, and aerosol enhanced chemical depletion accounts for most of the interannual variability in total ozone during northern winter. In particular, the {dollar}-{dollar}4% per decade trend observed prior to Mt. Pinatubo can be attributed largely to decadal changes in planetary wave driving of the Brewer-Dobson circulation. Differences in total ozone calculated from model integrations forced by planetary waves representative of the early 1980's and late 1980's reproduce both the magnitude and the structure of observed trends at northern midlatitudes during winter, supporting the results of the regression analysis. |
