Variations in the 18‐year (1971–1988) Hohenpeissenberg (Federal Republic of Germany) and the 33‐year (1956–1988) Arkona (German Democratic Republic) surface ozone data sets are analyzed. Over the full period of the records (as made available to us), both stations, which are about 800 km apart, show a positive long‐term trend of about 1.0% per year (strongest in winter at Hohenpeissenberg and in spring at Arkona). There are, however, marked differences in the fluctuations over various subperiods at the two locations. For example, the Hohenpeissenberg data show a larger increase in mean surface ozone concentration in the 1970s (about 2.1% per year, strongest in winter) compared with that in the 1980s (about 0.5% per year, strongest in summer). The Arkona data show a significant linear increase from 1956 to 1979 (about 2.4% per year, strongest in winter in the 1960s and in summer in the 1970s) but a linear decrease in the 1980s (about −2.4% per year, strongest in winter) and over the period 1971–1988 (about −1.2% per year, strongest in autumn and weakest in spring). The decrease is caused by the considerably lower concentrations in the 1980–1985 period when concentrations declined at about −10% per year. Over the same period 1971–1988, the seasonal cycle at Hohenpeissenberg exhibits a summer maximum in July (with a broad peak), while that at Arkona displays a spring maximum in May (with a sharp peak). The causes of these differences are likely to be complex: a combination of photochemistry (which depends on the distribution of precursors, particularly NOx), differences in surface deposition, local departures in the atmospheric circulation and, possibly, data quality. The pre‐1976 Hohenpeissenberg data and the pre‐1972 Arkona data (before filters were used to remove SO2) and the post‐1982 Arkona data (after a new measuring instrument was installed) may need to be further scrutinized to ensure consistency in data quality.

Daily surface ozone observations from 1978 (1976 for some analyses) to 1988 for Bottesford (United Kingdom), Cabauw, Kloosterburen (The Netherlands), Hohenpeissenberg, Neuglobsow, Hamburg, and Arkona (Germany) are used to analyze links between surface ozone variations and the atmospheric circulation. A daily Europe‐wide synoptic classification highlights marked differences between surface ozone/meteorology relationships in summer and winter. These relationships are characterized by correlations between daily surface ozone concentrations at each station and a local subregional surface pressure gradient (a wind speed index). Although there are geographical variations, which are explicable in terms of regional climatology, there are distinct annual cycles. In summer, the surface ozone/wind speed relationship exhibits the expected negative sign; however, in winter, the relationship is, in the main, strongly positive, especially at those stations which are more influenced by the vigorous westerlies. Spring and autumn exhibit negative, positive, or transitional (between summer and winter) behavior, depending on geographical position. It is suggested that these relationships reflect the importance of vertical exchange from the free troposphere to the surface in the nonsummer months. Composite surface pressure patterns and surface pressure anomaly (from the long‐term mean) patterns associated with high surface ozone concentrations on daily and seasonal time scales are consistent with the surface ozone/wind speed relationships. Moreover, they demonstrate that high surface ozone concentrations, in a climatological time frame, can be associated with mean surface pressure patterns which have a synoptic reality and are robust. Such an approach may be useful in interpreting past variations in surface ozone and may help to isolate the effect of human activity. It is also possible that assessments can be made of the effect of projected future changes in the atmospheric circulation. This potential is illustrated by the fact that up to 65% of the interannual variance in 6‐month mean surface ozone concentrations can be explained by the subregional wind speed index.

Surface ozone data from 20 European stations of differing character (remote, rural, suburban and urban) were analysed for linear trends over a common period of 1978–1988. Pronounced annual and seasonal variations are apparent in the trends in different areas. Relatively few of the trends are statistically significant and there is no dominant region‐wide trend. However, there does appear to be some commonality of behaviour on a subregional scale as positive or negative trends tend to be clustered together in some areas. Stations on the maritime fringe of the network generally exhibit negative trends in summer average concentrations, whilst those located further into the continental interior exhibit positive trends. Most of the stations in the network exhibit positive trends in the winter averages. The short‐term variability evident in this study reflects the complex controls affecting surface ozone concentration and suggests that it may be misleading to draw conclusions concerning long‐term trends from records of limited duration.

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