## 2 Materials and Methods
### Analysis of the Flow Field near the Ozone Valley over the TP Influenced by EN  
To understand the mechanism of EN's influence on the ozone valley in the UTLS layer over the TP, we compared the circulation fields at the 200 hPa layer for different types of EN events with the mean climate state in the summer of the following year, as shown in Figure 5.  
Under the influence of different types of EN, the positive (negative) abnormal regions of vorticity at the height layer of 200 hPa (Figure 5a-d) basically correspond to the positive (negative) abnormal regions of TCO at the UTLS layer of 300-50 hPa (Figures 4a, 4b, 4c and 4d, respectively), indicating that the positive (negative) abnormal vorticity at the layer of 200 hPa causes the increase (decrease) in TCO. In general, the positive vorticity of the upper atmosphere corresponds to the upward motion of the lower atmosphere. The strengthening of the upward movement of the lower atmosphere causes an uplift of the low-concentration ozone in the lower layer to the UTLS layer, resulting in a decrease in TCO. In the area south of 30\({}^{\circ}\) N, the circulation field at the 200 hPa level in the summer of the following year for each type of EN event is dominated by negative vorticity anomalies. The vorticity-positive anomaly area is mainly distributed near the 40\({}^{\circ}\) N zone, corresponding to the TCO-positive anomaly distribution area. Overall, the distribution of each subgraph south of the 50\({}^{\circ}\) N zone is roughly the same. Among them, the positive and negative vorticity anomalies corresponding to CP-type EN (Figure 5b) are weak in intensity, and the corresponding TCO anomalies are also weak, which is related to the weak intensity of CP EN events. Comparatively, north of 50\({}^{\circ}\) N, there are differences in the distribution of vorticity anomalies. From west to east near 55\({}^{\circ}\) N, in the following year after the EP-type EN event (Figure 5a), there is a positive vorticity anomaly on the southwest side of the Caspian Sea with a central intensity of 5.6 \(\times\) 10\({}^{-6}\)/s, a negative anomaly in the north of Kazakhstan and a positive anomaly in the north of Mongolia. After the SP-type EN events (Figure 5c),  
Figure 5: Abnormal distribution of wind fields at the 200 hPa altitude of different types of EN (**(a)**, EP; **(b)**, CP; **(c)**, SP; **(d)**, SU) in the summer of the following year through a 95% confidence test; unit: 10\({}^{-6}\)/s. The black line represents the characteristic line of the SAH in the summer of the following year of EN, and the yellow line represents the characteristic line of the SAH in the average climatic state. the negative vorticity anomaly is stronger only in central and southern Russia, which is more easterly than the negative TCO anomaly in the corresponding region (Figure 4c). After the SU-type EN (Figure 5d), a positive vorticity anomaly presents in the northwest of Mongolia and a strong negative vorticity anomaly occurs from south-central Russia to Eastern Europe, with a peak area of 13 \(\times\) 10\({}^{-6}\)/s. This corresponds to the high-value area of the negative TCO anomaly in Figure 4d. Considering that the SAH is an important weather system in the ozone valley region of the TP, and it has a certain interaction with the ozone [30], we marked the range of SAH in the summer of the following year under the influence of El Nino (black line in Figure 5) and the mean climate of 44 years (yellow line in Figure 5) for comparative analysis. Figure 5 shows that SAH strengthens in the summer of the following year under the influence of El Nino, and the vorticity in the region presents significant negative anomalies. Among them, the distribution areas of the negative vorticity anomalies in the SAH region corresponding to EP-type (Figure 5a) and SP-type (Figure 5c) El Nino events are larger, and the intensity of the high-value region of the anomalies is approximately \(-6.0\)\(\times\) 10\({}^{-6}\)/s. [PERSON] et al.