Horizontal and vertical profiles of ozone, carbon monoxide, non-methane hydrocarbons and dimethyl sulphide near the Mace Head observatory, Ireland

Abstract. The distribution of trace gases upwind and above the Mace Head Atmospheric Research Station, Ireland has been determined using measurements made from aircraft. The observations indicate excellent agreement between most non-methane hydrocarbons, dimethyl sulphide (DMS) and ozone measured at the surface, at 390 m overhead and in upwind boundary layer regions of the coastal Atlantic. Vertical profiles above the observatory indicated that local convective events result in a marine influence being detected at 3 km and above. The observation of isoprene from maritime sources at these levels was indicative of very rapid uplift on the hour timescale. Measurements of trace gases were also made directly upwind of the observatory over coastal regions and as far as the deep open ocean beyond the continental shelf. A maximum of 240 pptV DMS was observed in the boundary layer near to the shelf region, declining to a concentration of around 40 pptV at the coastline. The upwelling of nutrient rich waters at the ocean shelf location may be a possible explanation for the high abundance of DMS in these regions. The observations suggest that this region, some 150–200 km from the observatory, would under these environmental conditions have a major influence in the determining the DMS observed on-shore. The spatial distribution of ethene within boundary layer over coastal and deep waters differed significantly from DMS with an almost uniform abundance over all ocean regions.