## 5 Summary and Discussion  
### Summary  
In this study, the SST data of ERA5 are used to record and classify the EN events in the period of 1979\(-\)2022. Combined with the data of the ozone and circulation field, we analyzed the influence of different types of EN events on the ozone valley over the TP. Moreover, the simulation results of the WACCM4 mode further support our conclusions, which are summarized as follows:  
1. During 1979\(-\)2022, there were a total of 10 EN events. From the perspective of event establishment time, there are seven SP-type EN events and three SU-type EN events. According to the spatial pattern of SST anomaly distribution, there were five events of the EP type and CP type, respectively. Overall, the EP (SP)-type events were more intense and lasted longer than the CP (SU)-type events.
2. In the summer of the following year after the peak of EN, the ozone valley in the UTLS layer over the TP has a significant change, showing an overall zonal distribution. The calculated differences in TCO show that, on the whole, after EN events,  
Figure 9: Latitudinal profile of differences in summer wind velocity of the following year between sensitivity experiments of different types of EN in WACCM4 mode ((**a**), EP-CP; (**b**), SP-SU). The vertical wind speed is the result of magnification 500 times.  
the TCO near the low latitude (0-30\({}^{\circ}\) N) presents negative anomalies and becomes stronger nearer to the equator. The TCO variation north of 30\({}^{\circ}\) N is mainly a positive anomaly with the high-value area at approximately 40\({}^{\circ}\) N, which weakens the ozone valley phenomenon.
3. The effects of different types of EN events on ozone in the TP region are distinct in nature and intensity. The EP-type EN is closer to the overall distribution, whereas the distribution of the TCO anomalies of CP-type EN is different from the whole picture. In the range of 10-50\({}^{\circ}\) N, the TCO anomaly value is positive, but the overall TCO anomaly value is small. The negative TCO anomaly caused by SP-type EN in low latitudes is weak. The overall effect of SU-type EN is the strongest, with the TCO positive anomaly centered near the Caspian Sea and strong negative effects in the belt from southwest Russia to Eastern Europe.
4. The positive (negative) TCO anomaly in the UTLS layer over the TP in the summer of the following year of EN corresponds to the positive (negative) vorticity anomaly at 200 hPa. In the summer of the following year, at low latitudes, the updraft corresponding to the vorticity anomaly lifts the low-concentration atmosphere of the lower layer to the UTLS layer, resulting in a decrease in the TCO. At the same time, EN causes SST to rise in the Indian Ocean, which enhances the SAH through the two-stage thermal adaptation and then decreases the ozone concentration in the southern low-latitude region of the SAH through the SAH-ozone interaction.
5. The simulation results of WACCM4 are overall consistent with the observed results, and the vertical profile results further explain the differences between different EN events. Compared with the CP (SU)-type EN events, the middle and upper atmospheric upward movement in the 20\({}^{\circ}\) N region near the TP in summer is stronger in EP (SP)-type EN events, and the corresponding SAH is also stronger. Both of these result in a wider range of negative TCO anomalies in the southern low latitude areas.