"Date completed: March 1991." Includes poem by Ron Baird, sculptor, on p. [4] of cover. Includes bibliographic references (p. 66) "ARD-91-002."

This report presents a comparison between O3, SO2, NO2, and H2O2 data collected at the Egbert and Dorset surface sites and data collected on board the DC-3 and Twin Otter aircraft during the summer 1988 intensive measurement period of EMEFS. During the afternoon, surface concentrations of O3, SO2, and NO2 agreed well with concentrations measured 100-300 m above the surface sites. A sharp drop (2-4 times) in H2O2 concentration was seen from the base of the profile to the surface. At night, approximately twice the surface SO2 is seen at the base of the profile. Significantly less O3 and more NO2 are seen at the surface than at the profile base at night. A composite picture of chemical concentrations during the afternoon and night is also presented in the form of median concentration profiles for air masses originating in the south, west, or north. Twin Otter profiles were grouped as a function of time and of the sector of the end points of the 925 mb, 24-hour back trajectories. Ozone concentrations are lower under the northerly flow than westerly or southerly flow. Median concentrations are approximately 25-30 ppbv larger in the southerly sector than in the northerly sector. Several ppbv of SO2 are seen in the south-sector throughout the mixed layer. H2O2 concentrations are approximately 1 ppbv in the north and west sectors. For the south sector, the concentrations reach several ppbv. Night-time profiles show a persistence of H2O2 aloft. NO2 concentrations are about 1 ppbv in the south sector but are less than 1 ppbv in the north and west sectors. For an approach to model evaluation, it is recommended that the ADOM predictions be binned as were the aircraft data to produce typical concentration profiles under different conditions. Agreement between the typical profiles as determined from the data and from the model should be expected.