中文摘要：

分析SAGE II资料发现：青藏高原对流层顶最高不超过17.6 km,夏季平均在17 km以下：来自对流层中低层的物质很少能被输送到17.5 km以上,来自对流层中低层的输送不会长时间持续地影响17.5 km以上的区域。青藏高原以及同纬度地区在15 20 km高度温度低于210 K,非均相化学反应可能在此起着重要作用。夏季青藏高原臭氧低谷的形成高度主要是15—20km,而且是长时间持续性的。分析结果显示：15—20km非均相化学过程在夏季青藏高原臭氧低谷的形成中可能起重要作用,特别在17.5—20km高度其所起的作用可能是主要的;而在17.5 km以下,从以往的研究可以知道青藏高原的动力和热力作用对夏季青藏高原臭氧低谷的形成起着主要作用。在春季和秋季,青藏高原上15—20km的臭氧＂亏损＂也可能是由于非均相化学过程造成的,使得青藏高原臭氧低谷每年从4月持续到10月。并且,影响非均相化学过程的主导因素可能是温度。

英文摘要：

Based on the SAGEⅡdata,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 imporlant 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 imporlant 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.