## 4 Causes of Influence of Different Types of EN on the Ozone Valley Based on WACCM4
The TCO under the influence of SP-type EN has a certain negative anomaly in the northwest of the Caspian Sea, which is farther west than the observed location. TCO anomalies in CP-type (Figure 7b) EN events differ significantly from observations (Figure 4b) in the region north of 40\({}^{\circ}\) N. In the simulation results, compared with the control experimental results, TCO has a strong zonal negative anomaly of approximately \(-\)1.1 DU. Furthermore, the peak area is located northwest of the Caspian Sea and Mongolia region, at \(-\)1.6 DU. Compared with the observation data, the negative anomaly of TCO is greatly enhanced and the distribution area is larger. Simulations are improved north of the equator to 40\({}^{\circ}\) N, where the TCO anomaly is a weak negative-positive distribution from south to north, consistent with observations. Figure 8 shows the difference between the 200 hPa flow field simulated by WACCM4 and the controlled experimental climate state in the summer of the following year impacted by different types of EN. Impacted by EP-type (Figure 8a), CP-type (Figure 8b) and SU-type (Figure 8d) EN events north of the equator to 20\({}^{\circ}\) N, the flow field presents zonal negative vorticity differences with an intensity of approximately \(-\)4 \(\times\) 10\({}^{-6}\)/s, which is in good agreement the observed results. After the SP-type (Figure 8c) EN event, an irregular distribution of positive and negative phases at low latitudes occurs. The simulation has amplified these sporadic weak positive vorticity anomalies in the observations, resulting in a more intense and wider distribution. At 30\({}^{\circ}\) N-40\({}^{\circ}\) N, the simulation of the four cases is better and shows consistent positive vorticity anomalies of approximately 6 \(\times\) 10\({}^{-6}\)/s; this is in good alignment with the distribution of observed results. At 50\({}^{\circ}\) N-60\({}^{\circ}\) N, the negative vorticity anomaly is dominant, corresponding to the observed value but with the location slightly shifted. Over the whole region near the ozone valley of the TP, the simulated 200 hPa circulation field anomaly is overall consistent with the observed value, except for substantial positive anomalies of the SP simulation experiment at a low latitude. To demonstrate the difference in atmospheric movement over the TP under different types of EN events, the wind fields of the four WACCM4 sensitivity experiments were zonally averaged within 20\({}^{\circ}\) E-120\({}^{\circ}\) E. Thus, the zonal and vertical differences in wind speed between the EP and CP types (Figure 9a) as well as the SP and SU (Figure 9b) types of EN events in the summer of the following year are obtained. In the vicinity of 20\({}^{\circ}\) N, EP- and SP-type EN events correspond to a stronger upward movement of the mid-upper atmosphere in the following summer. Meanwhile, the SAH also becomes stronger. These have led to a wider range of negative TCO anomalies, consistent with the observation results (Figure 4) and simulation results (Figure 7). In summary, the distribution of TCO and flow field at 200 hPa in the summer of the following year of EN simulated by the WACCM4 mode is consistent with the observed results. Furthermore, the positive (negative) vorticity anomalies at this height can correspond to the positive (negative) TCO anomalies. Moreover, the results of the simulation show that in the summer of the following year after EP (SP)-type EN, compared with CP (SU)-type EN, more low-concentration ozone is lifted into the stratosphere due to stronger atmospheric upward movement; the SAH is also stronger during this period, resulting in a larger range of negative TCO anomalies on the south of the TP.