MEASUREMENTS OF OZONE AND OTHER RADIATIVELY ACTIVE GASES AT MACE HEAD IN THE REPUBLIC OF IRELAND

Since 1987 measurements of ozone, methane, nitrous oxide and the principal man-made halocarbons have been collected at Mace Head on the Atlantic Coast of the Republic of Ireland as part of the Global Atmospheric Gases Experiment (GAGE). A longer time series of nitrous oxide and halocarbon measurements were obtained at Adrigole, also on the west coast of Ireland, from 1979 to 1983 as part of the Atmospheric Lifetime Experiment (ALE). At both these sites significant correlations between individual trace gases are observed during periods of substantial regional pollution, which occur about 30% of the time, when the wind flow is predominantly from a southeasterly to easterly direction. Although the concentration of ozone increases substantially during anticyclonic sunny weather, it has also been observed that almost complete destruction of ozone can occur during anticyclonic weather if there is little or no sunshine. By utilizing the daily wind sector allocations for the closest UNECE EMEP monitoring sites, it has been possible to sort the time series concentration data according to the air mass trajectory. A clear association of halocarbon concentration with wind direction was observed demonstrating the influence of heavily populated centres to the east and south of this remote site. It was more surprising to find a similar wind direction association with the data for nitrous oxide, methane, and ozone. The magnitudes of the respective man-made European source strengths of these important radiatively-active gases have been estimated, based on the halocarbon concentrations.