Characteristics Of The Ozone Vertical Distribution And A Case Study At The Northeastern Tibetan Plateau

Using the ozone and temperature sounding data, NCEP/NCAR data, OMI satellite observations of total ozone column and back trajectories calculated with NOAAHYSPLIT model, the characteristics of the ozone and temperature vertical distributions in Xining and Lanzhou of northeastern Tibetan Plateau are investigated and the main results are as following:(1) This study also investigates the factors and processes affecting ozone vertical profiles near the Tibetan plateau through a case study. The analysis suggests that dynamic transport is the main factor which influences the ozone vertical distribution over the Tibetan Plateau. In particular, the invasion of air from the high latitude to the south will lead to increases in ozone concentration over the Tibetan Plateau and affect the range and shape of'ozone valley'over the Tibetan plateau. Although the impact of chemical processes on ozone concentration over the Tibetan Plateau is not significant in the lower stratosphere, the analysis indicates that the ozone changes are in good accordance with ozone changes in the stratosphere. The analysis also reveals that downward invasion of the stratospheric air into the troposphere is likely to occur near the edge of high pressure systems, particularly for those strong quasi-stationary anti-cyclone systems at middle and high latitudes. This invasion of stratospheric will cause increases of the ozone concentration in the troposphere.(2) Total of 36 sounding profiles of ozone and temperature gathered at Xining in 1995 to 1996 and 9 profiles gathered at Lanzhou were analysed. The results show that the bulk characteristic of temperature and ozone vertical distributions at the two sites are in a good agreement. The temperature and ozone reach their minimum at around 17 km above sea level, while the maximum ozone partial pressure is observed at around 25 km above sea level. The ozone mixing ratios reach a maximum at 30 km above sea level. The variability of ozone vertical distributions in Lanzhou is much larger than those at Xining. Ozone concentrations in the stratosphere in spring and winter are higher than those in summer and autumn. The tropospheric ozone concentrations reach the highest in summer. The tropopause height in winter and spring is about 12 km and but can reaches 17 km in summer. In winter and spring, due to the existence of secondary peak of ozone in the troposphere and lower stratosphere, vertical distributions of ozone become more complex. The differences in air pollution conditions in the two cities and different observational situations result in large differences in total column ozone, tropospheric ozone column between two sites.