Synoptic weather types and long-range transport patterns for ozone precursors during high-ozone events in southern Sweden.

We studied long-range transport patterns and related weather types in relation to high-ozone events in southern Sweden. The aim was to deepen the understanding of the relationship between Lamb-Jenkinson weather types and surface ozone concentration variation, thus widening the application of the weather type analysis of air quality at 4 sites in this region. The long-range transport patterns associated with high-ozone events were classified into trajectories from Western Europe, Eastern Europe, and in the vicinity of southern Sweden (VIC). The VIC type, characterized by short and whirling curves, represented more than 40% of the high-ozone events at the studied rural sites. More than half of the high-ozone events occurred under high-pressure conditions, belonging to weather type A (anticyclones). The high correlation coefficient between annual counts of weather type A and those of long-range transport pattern VIC confirmed the strong link between stagnant weather conditions and high-ozone events, especially during the summer. Furthermore, a strong linear anticorrelation was detected between high-ozone events and annual counts of weather type C (cyclones) during the summer. This relationship implies that the frequency of weather type C is a useful indicator for low risk of summertime high-ozone events in southern Sweden. Moreover, the relationship between the weather type and high ozone risk may be useful in examining the potential effect of climate change on the regional air quality.