Abstract

The AGAGE (Advanced Global Atmospheric Gases Experiment) observation station at Mace Head (53°N, 10°W) on the west coast of Ireland is ideally situated to observe long-term trends in trace gas concentrations. The station meteorology is dominated by westerly winds that allow it to frequently sample well-mixed Northern Hemispheric air masses. These observations are isolated and used to estimate mid-latitude Northern Hemisphere baseline concentrations of a wide range of trace gases, most notably the principle greenhouse gases; carbon dioxide, methane, nitrous oxide, ozone and the principle ozone-depleting gases; CFCs, HCF Cs.

The air mass sorting requires knowledge of the recent history of the air mass that is sampled and this is obtained from the NAME model (Numerical Atmospheric dispersion Modelling Environment). This is the Met Office’s Lagrangian atmospheric dispersion model that can use 3-D meteorology from either the Met Office’s or ECMWF ’s numerical weather prediction models.

On a reasonable number of days (~30%) Mace Head receives air from the UK and the continent. By using inversion modelling it is possible to estimate the source strengths and geographical distributions of the emissions that provide the best statistical match to the observed above-baseline ‘pollution’ events.

In this way surface observations can be used to validate the reported inventory-based “bottom-up” emissions required through the Kyoto Protocol process.