1] The effect of the 11-year solar cycle on the troposphere-stratosphere (TS) coupling in the Southern Hemisphere (SH) late winter/spring is examined through the analysis of observations and simulations with a chemistry-climate model. It is found that the TS coupling in the SH late winter/spring is significantly modified according to the solar cycle; the dynamical coupling between the troposphere and stratosphere becomes stronger with the increasing solar activity. Such modulation of the strength of the TS coupling is found to be the source of the solar-cycle modulation of the annular mode in late winter/spring. A possible mechanism of the solar-cycle-TS-coupling relationship is also discussed.