Aircraft studies of atmospheric chemistry over the North Atlantic

In this thesis, the broad topic of atmosphere chemistry over the Northern Atlantic is considered, especially using trace gas climatologies as indicators of the influence of continental outflow of anthropogenic pollutants on the composition and chemistry of this region. The data described were obtained during recent aircraft measurements campaigns conducted aboard the UK MRF C-130 Hercules platform, under the auspices of the UK-NERC ACSOE (Atmospheric Chemistry Studies in Oceanic Environment) and the EU MAXOX (MAXimum OXidation rates in the free troposphere) campaigns. Instruments mounted on this aircraft platform provided in situ measurements of the concentrations of O3, NOx, NOy, H2O2, CH3OOH, CO and HCHO in the free troposphere over the North Atlantic. This thesis describes, in part, the validation of measured modelled trace gas distributions via trace gas climatologies over the broad latitude range 20°N to 60°N by way of data bins ranging from 0-8 km. This climatological analysis provides an insight into the distribution of trace gas in this region, especially on a seasonal basis. Results suggest a number of photochemical tracers show pronounced seasonal variation over altitudes less than 8km. The exact nature of this seasonal variation is discussed, along with possible evidence of a wide spread photochemical source for a pronounced springtime ozone maximum in these environments.;The validation of aircraft measurements has been investigated via model analysis. Climatology data has been compared to the outputs of a chemistry transport model. This work shows that for some tracers the model is able to reproduce measured values with a high degree of accuracy..