Abstract: Long-term trends of yearly and seasonal averages of tropospheric ozone over the whole country and some important regions of China during 1979-2005 were analyzed, based on the tropospheric ozone residue (TOR) data retrieved from satellite measurements. The relationship between TOR and the Southern Oscillation Index (SOI) was studied. The results show that, over the whole country, there was a slight increase of TOR in summer and a decrease in other seasons, while the overall trend for the whole period was insignificant. There were decreasing trends of TOR over the Pearl River Delta and the Sichuan Basin. Significant increasing trends of TOR were found over the North China Plain for all seasons except winter, with a maximum rate of 1.10 DU/10a for summer. There were significant correlations between TOR and SOI for some Chinese regions but not for the North China Plain, suggesting that the observed increasing trend of TOR over the North China Plain may not be linked with changes in atmospheric circulations.

Key words: China, tropospheric ozone, change trend, SOI