The Impact of Different Types of El Ni?o Events on the Ozone Valley of the Tibetan Plateau Based on the WACCM4 Mode

This study integrates the sea surface temperature, ozone and meteorological data of ERA5 to count the El Nino events since 1979 and has classified these events into eastern and central types in space as well as spring and summer types in time. The impacts of different types of El Nino events on the ozone valley of the Tibetan Plateau are discussed. The eastern (and spring) type of El Nino events are generally more intense and longer in duration than the central (and summer) type of El Nino events. Overall, in the summer of the following year after El Nino events, the total column ozone (TCO) anomalies near the Tibetan Plateau have a regular zonal distribution. At low latitudes, TCO exhibits negative anomalies, which become more negative approaching the equator. The TCO in the region north of 30 degrees N mainly shows positive anomalies with the high-value region around 40 degrees N. The responses of ozone to different types of El Nino events over the Tibetan Plateau are different, which is further validated by the WACCM4 simulation results. The greater intensity of the eastern (and spring) type of El Nino events caused stronger upward movement of the middle and upper atmosphere in the 20 degrees N region in the subsequent summer as well as a stronger South Asian High. These have resulted in a wider range of negative TCO anomalies in the southern low-latitude region of the South Asian High. In addition, the growing intensity of El Nino extreme events over more than half a century warrants significant concern.