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3. Parameter Sweep Experiment

The parameter sweep experiment reveals that the stratospheric circulation depends on h0 in its mean seasonal march and interannual variability. The mean seasonal march of the zonal mean temperature in the polar upper stratosphere is highly dependent on h0 in cold seasons from autumn to spring (not shown). In the run of h0 = 0 m without the topography, the mean polar temperature only follows the annually-varying radiative forcing with a time lag of about several days. As h0 is increased to h0 ¡Á700 m, the polar temperature largely departs from the radiatively-determined state in spring, but the departure is small in winter. As h0 is further increased up to h0 = 3000 m, large departures appear in winter; the minimum temperature during the season becomes higher, while its timing becomes earlier.

Interannual variability is large in different seasons dependent on h0 (Fig. 1). In the run of h0 = 0 m, the interannual variability is small in all seasons. As h0 is increased to h0 ¡Á500 m, the polar temperature comes to show large variability in spring. The variability is extremely large during winter in the runs of larger h0. These results remind us of the interannual variations in the real stratosphere; the interannual variability in the run of h0 = 500 m resembles that in the real SH stratosphere, while the variability in the run of h0 = 1000 m does that in the NH stratosphere.