A possible effect of heterogeneous reactions on the formation of the ozone valley over the Tibetan Plateau

Based on the SAGE II data, it is found that the highest tropopause height over the Tibetan Plateau (TP) is lower than 17.6 km, and the averaged tropopause height is lower than 17 km over summer. Moreover, matters from the middle and low troposphere are hardly transported into above 17.5 km, in other words, the transport from the middle and low troposphere might not continuously affect the region above 17.5 km. As temperatures from 15 km to 20 km over the TP and the zone of same latitude are less than 210 K heterogeneous reactions might play an important role in ozone variations. The ozone valley over the TP in summer results from low ozone concentration from 15 km to 20 km over the TP, and it maintains over a long period of time. The analysis suggests that the heterogeneous reactions from 15 km to 20 km might play an important role in the ozone valley formation over the TP in summer, especially from 17.5 km to 20 km. As for below 17.5 km, the previous researches indicate that dynamic and thermodynamic effects of the TP play an important role. In spring and autumn heterogeneous reactions might result in ozone “lose” from 15 km to 20 km over the TP, so the ozone valley over the TP continues from April to October. Temperature might be the main factor that influences heterogeneous reactions.