Changes in tropospheric ozone levels over the Three Representative Regions of China observed from space by the Tropospheric Emission Spectrometer ( TES ) , 2005 2010

Tropospheric ozone observations over China from 2005 to 2010 at three pressure levels (484, 681 and 825 hPa) from the Tropospheric Emission Spectrometer on board the NASA Aura satellite have been analyzed. Fourier Transform analysis revealed the trends and seasonality of regionally-averaged, monthly-mean ozone concentrations over western, northern and southern China. Significant increases in ozone levels are found over all three regions at 464 hPa and the rate of increase is fastest over northern China, reaching 0.89±0.059 nL/(L a). At 681 hPa, ozone shows increases over northern and western China, at a rate of 0.57± 0.065 nL/(L a) and 0.41±0.041 nL/(L a) respectively, but is constant over southern China. At 825 hPa, ozone increases at a rate of 0.36±0.074 nL/(L a) over northern China, while decreasing over southern China at a rate of 0.21±0.061 nL/(L a). Over the three regions, ozone levels are generally higher in summer and lower in winter. Over southern China at all three pressure levels and northern China at the 825 hPa level, ozone shows double peaks occurring in spring and autumn as a result of the combined effects of atmospheric chemistry and global transport. This work provides a useful observational dataset and tools for future analysis of changes in tropospheric ozone over China.