Downward influence of stratospheric final warming events in an idealized model

An idealized atmospheric model is used to simulate the stratospheric final warming events by imposing a radiative equilibrium temperature transition from winter to summer only in the stratosphere. Large ensembles of final warmings reveal that the final warming onset dates become earlier and the downward influence structure strenghtens, as the topographic amplitudes increase, similar to the differences between Southern and Northern Hemisphere. The mechanisms of the downward influence of the final warmings on the tropospheric circulation are investigated in a zonally symmetric model. Results imply that stratospheric wave driving can induce a residual circulation and affect the tropospheric circulation. The tropospheric signals due to this mechanism are, however, not enough for the full tropospheric response. On the other hand, the stratosphere can also affect the propagation of planetary waves from the troposphere, resulting in a burst of wave activity and the zonal wind deceleration in the troposphere.