Analysis of tropospheric ozone measurements in Greenland

The Danish Meteorological Institute (DMI) initiated continuous measurements of surface ozone concentrations in Greenland during spring 1994 as a part of the EU-project ARCtic Tropospheric Ozone Chemistry (ARCTOC). In 1995 and 1996, several events of deep ozone depletion were recorded at Thule and Søndre Strømfjord connected with passing frontal systems (cold fronts) from the west or north-west with rising pressure and falling temperature. At Scoresbysund, minor episodes were observed both in 1995 and 1996. The major episodes could definitely be assigned to cold air masses moving from the Arctic Ocean over the Canadian Archipelago across Baffin Bay and Davis Strait and further crossing Greenland. Analyses of backward trajectories calculated by a 3-D transport model developed at DMI utilising meteorological data from the numerical weather prediction model DMI-HIRLAM (HIgh Resolution Limited Area Model) have been performed. Results from these studies show that air parcels with low ozone values at the receptor point generally have passed the northern Canadian Archipelago or the Arctic Ocean a few days before the arrival at the receptor point.