## 4 Causes of Influence of Different Types of EN on the Ozone Valley Based on WACCM4  
The SST fields corresponding to each category of events (Table 1) are monthly averages over 24 months following January at the beginning year, obtaining the SST fields for the four categories with a duration of 24 months (Figure 6). Then, the SSTs for months with an SSTA greater than or equal to 0.5 \({}^{\circ}\)C are retained, while the SSTs for other months are synthesized with normal years. This process yields four new SST sequences of 24 months. Subsequently, the SSTs of three normal years are linked to form an EN event with a five-year cycle. Repeating this procedure on a five-year cycle generates multiple EN events to simulate EN signals. This is an ideal experiment, with the period of 1955-2005, and the SST forcing region applied is 15\({}^{\circ}\) S-15\({}^{\circ}\) N, 135\({}^{\circ}\) E-80\({}^{\circ}\) W. The scale of the simulation is global. In four sensitivity experiments (E1, E2, E3 and E4), we introduced the four types of EN SST synthesized above to the forced region to simulate the ozone response to different types of EN events over the TP. To balance the mode, in the first five years (1955\(-\)1959), a consistent normal SST was added as the mode start-up phase. Subsequently, from 1960 to 2005, nine synthetic EN event SSTs were added on a five-year cycle as the SST forcing of the sensitivity test, which was used to replace the SST forcing data specified in WACCM4 for simulation experiments. In this way, we can obtain nine simulated values of the Tibetan high-pressure ozone valley and circulation field in the summer of the following year corresponding to the four types of EN events. Meanwhile, to facilitate comparative analysis, in the controlled experiment (E0), we input the normal SST for simulation during the whole experimental period. The ozone and flow field data of 51 years from 1960 to 2005 were analyzed. The specific experimental design scheme is given in Table 3. Finally, we compared the nine simulated values of ozone and circulation field over the TP in the summer of the following year corresponding to the four types of EN events. This was simulated by sensitivity experiments with the results  
Figure 8: Difference test between 200 hPa flow field and control experiment results of sensitivity experiment of different types of EN ((**a**), EP; (**b**), CP; (**c**), SP; (**d**), SU) in WACCM4 mode in the summer of the following year. The colored region is the vorticity for which the difference passes the 95% confidence test; unit: \(10^{-6}\)/s. Figure 7: Difference test between TCO and control experiment results of sensitivity experiments of different types of EN ((**a**), EP; (**b**), CP; (**c**), SP; (**d**), SU) in WACCM4 mode in the following summer. The dotted areas indicate that the differences pass the 95% confidence test; unit: DU. The comparison between the simulation results (Figure 7) and the observations (Figure 4) shows great disparities between the TCO and the mean climate results in the summer of the following year of EN. And the simulated values generally align well with the observed results. From the equator to 30\({}^{\circ}\) N, the simulated TCO presents a uniformly negative zonal anomaly of approximately \(-\)0.3 DU in the following summer after EP-type (Figure 7a), SP-type (Figure 7c) and SU-type (Figure 7d) EN events. This is consistent with the distribution of observation (Figure 4). There are alternating positive and negative differences between 40\({}^{\circ}\) N and 60\({}^{\circ}\) N. Under the influence of EP- and SU-type EN events, the TCO is a consistent zonal positive anomaly near 40\({}^{\circ}\) N. The signal is strong at approximately 0.8 DU, with the peak area located on the west side of the Caspian Sea and northeast China, and highest at 1.2 DU, consistent with the observed distribution area. There are weak negative anomalies in the TCO near Kazakhstan at 50\({}^{\circ}\) N and in the western area of central Russia, and positive ones on the other east and west sides.