TRENDS OF STRATOSPHERIC OZONE AND AEROSOLS OVER TIBETAN PLATEAU

It is found from the analysis of SAGE II dataset that there was a decreasing trend of stratospheric ozone over the Tibetan Plateau (TP) in 1985-2004. The changes in total column ozone mainly resulted from the ozone from 15 km to 50 km, wherein the role of the ozone from 25 km to 50 km was almost equal to that from 15 km to 25 km. From comparing the ozone changes between the TP and east part of China (ECHN), it can be clearly seen that the differences between the two areas was mostly ascribed to the difference of ozone changes from 15 km to 25 km. The trend for May to July was similar to that for yearly average, and the difference of trends between the two areas also mainly occurred in the low stratosphere from 15 km to 25 km. Time serials of aerosol area density over the TP show that big volcanic eruptions significantly affected the stratospheric aerosols over the TP, and the influences continuously lasted for about 6 years. Since 1997 the aerosol area density has increased between 18 km and 25 km over the TP, with a maximum growth of about 4% to 5% per year at 23 km, but decreased between 16 km and 17 km. Meanwhile, the temperature below 37 km has decreased over the TP, and it decreased faster over the TP than over the ECHN. From 37 km to 50 km, the temperature has increased, and it increased faster over the TP than over the ECHN. Both the aerosol increase and temperature decrease in the low stratosphere over the TP would all enhance the role of heterogeneous reactions.