## 2 Materials and Methods
### Characteristics of the Ozone Valley over the TP Affected by Different Types of EN Events
The stronger anomaly is located in the western area of Central Russia, northeast of the Caspian Sea, with a central intensity of \(-\)0.22 DU. The regular zonal distribution of the TCO anomaly shown in Figure 3b is related to the changes in BD circulation under the influence of EN. The upward center of the BD circulation in summer moves northward from the equatorial region to approximately 10\({}^{\circ}\) N. During EN, SST rises, and the upward motion generated by the tropical ocean-atmosphere convection is strengthened. These intensify the BD circulation, thus promoting the upward motion of the lower atmosphere at the equator and low latitudes. Consequently, more low  
Figure 3: Anomaly of ozone valley over the TP in the summer of the following year of EN during 1979\(-\)2022 ((**a**), TCO*; (**b**), TCO). The black dots indicate that the difference passes the 95% confidence test; unit: DU. concentration ozone at the lower level ascends to the upper level, resulting in a decrease in TCO in the UTLS region. This change corresponds to the negative TCO anomaly of a unified zonal band from north of the equator to near 30\({}^{\circ}\) N, as shown in Figure 3b. In the region north of 30\({}^{\circ}\) N, due to the strengthening of BD circulation, the atmospheric upward motion will reach a higher height and fall to a more northerly latitude. This will cause a higher-concentration stratospheric ozone in the equatorial region to be transported to the middle and high latitudes and then sink to the UTLS layer, corresponding to the TCO positive anomaly north of 30\({}^{\circ}\) N in Figure 3b. According to the EN categories mentioned above, we separately tabulated the ozone corresponding to the peak values of different types of EN events in the summer of the following year. Subsequently, we conducted the distinct difference test between Figure 3b and the mean climate for each category. In essence, Figure 3b is deconstructed into four modes based on EN types, and the results are depicted in Figure 4.  
Various types of EN events exert distinct effects on TCO changes over the TP. As is shown in Figure 3, EP-type EN events (Figure 4a) align with the overall difference in intensity and spatial distribution, with negative anomalies in the southern part of the TP and positive anomalies in the northern part. The range of negative anomalies in the low latitudes extends northward to 30\({}^{\circ}\) N, and the weak negative values in the Mediterranean region disappear. The intensity of CP-type EN events (Figure 4b) is generally weak, with a distribution pattern of TCO anomalies distinctive from the overall EN. Influenced by CP-type EN events, TCO in the summer of the following year presents a weak positive anomaly in the region near the Tibetan high pressure, where the high value is still around 40\({}^{\circ}\) N of approximately 0.2 DU. The positive anomalies at low latitudes near the equator and the negative anomalies near 60\({}^{\circ}\) N are weak and insignificant. Temporarily, the negative anomalies of TCO at low latitudes caused by SP-type EN events (Figure 4c) are weak and not significant. The mid-latitude anomaly is similar to the overall EN. The SU-type (Figure 4d) EN event has the strongest influence, and its TCO positive anomaly center is located near the Caspian Sea, with a value of 0.4 DU. There is a strong negative anomaly from southwest Russia to Eastern Europe, with a value of \(-0.8\) DU. In conclusion, EN events have significant impacts on the ozone valley over the TP. Moreover, the effects of different types of EN are different in intensity and nature, implying  
Figure 4: Anomaly of ozone valley over the TP under the influence of different types of EN. The black dots indicate that the difference passes the 95% confidence test; unit: DU. distinct internal influence mechanisms. This prompts further discussion on the influence of diverse types of EN on the ozone valley over the TP.