Abstract

In order to interpret the atmospheric chemistry measured at long term ground-based stations, the recent pathway of the air masses reaching the site must be noted. In the past this was often done using the wind direction measurements at the site, but these measurements represent the very recent air mass pathways and are often perturbed from the long term pathways by local effects such as sea breeze effects and topography.

A comparison of various techniques for tracking the origin of the air masses are shown, including wind directions, trajectories and dispersion models, with a more detailed description of the Met office’s NAME dispersion model. Interpretation of the changing air mass influences at various stations (Weybourne, London, Cape Verde and Halley) using the NAME model can help to understand pollutant episodes or just long term trends in certain atmospheric species passing over specific regions.

Examples for the sites in non polar regions are shown as well as a year round 10 day backwards record of the air mass pathway of air arriving at Halley, Antarctica are shown.