Abstract
Abstract. Information about the long-term trends of surface and tropospheric ozone is important for assessing the impact of ozone on human health, vegetation, and climate. Long-term measurements from East Asia, especially China's eastern provinces, are urgently needed to evaluate potential changes of tropospheric ozone over this economically rapid developing region. In this paper, surface ozone data from the Linan Regional Background Station in eastern China are analyzed and results about the long-term trends of surface ozone at the station are presented. Surface ozone data were collected at Linan during 6 periods between August 1991 and July 2006. The seasonality and the long-term changes of surface ozone at the site are discussed, with focus on changes in the diurnal variations, the extreme values, and the ozone distribution. Some long-term trends of surface ozone, e.g. decrease in the average concentration, increase in the daily amplitude of the relative diurnal variations, increase in the monthly highest 5% of the ozone concentration, decrease in the monthly lowest 5% of the ozone concentration, increase in the frequencies at the high and low ends of the ozone distribution have been uncovered by the analysis. All the trends indicate that the variability of surface ozone has been enhanced. Possible causes for the observed trends are discussed. The most likely cause is believed to be the increase of NOx concentration.
Highlights
Ozone is one of the key species in the atmosphere
The background stations of the Global Atmosphere Watch (GAW) are suitable sites for monitoring the long-term change of surface ozone because they are usually situated at places less directly influenced by anthropogenic emissions
Data used in this study were collected at the Linan Regional Background Station (30◦18 N, 119◦44 E, 139 m a.s.l.), one of the regional GAW stations in China, established and operated by China Meteorological Administration (CMA)
Summary
Ozone is one of the key species in the atmosphere. It absorbs both solar UV and terrestrial IR radiation, protects living organisms at the Earth’s surface against the harmful solar UV radiation and influences the energy budget of the atmosphere (Staehelin et al, 2001). The background stations of the Global Atmosphere Watch (GAW) are suitable sites for monitoring the long-term change of surface ozone because they are usually situated at places less directly influenced by anthropogenic emissions. Most background stations with long-term monitoring of surface ozone are located in North America and Europe, while only a few are located in some other important parts of world, e.g. East Asia. Studies of long-term trends of tropospheric ozone in East Asia are mainly based on ozonesonde data over Japan (Oltmans et al, 1998; Logan et al, 1999; Naja and Akimoto, 2004) and on MOZAIC aircraft data obtained in northern China (Ding et al, 2008). Besides the trend of surface ozone level, we discuss the long-term changes of the diurnal variation of surface ozone, which have seldom been touched by earlier studies
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