| Mid-latitude cyclones export the bulk of North American trace gases to the western North Atlantic Ocean (WNAO) atmosphere. Despite numerous case studies of trace gas transport to the WNAO, the literature lacks a comprehensive understanding of the typical trace gas signatures of mid-latitude cyclones. The North Atlantic Regional Experiment (HARE) produced aircraft-based trace gas measurements from mid-latitude cyclones during 1993, 1996, 1997 and 1999. This dissertation explores the NARE data in terms of cyclone airstreams and presents a coherent picture of trace gas export to the WNAO in the form of a conceptual cyclone model. The model, a composite of chemical measurements from several cyclones, has four main purposes: (1) separate the meteorological influences on airstream trace gas signatures from the influence of surface emissions heterogeneity; (2) present characteristic ozone, CO and NO y mixing ratios of the airstreams within a typical mid-latitude cyclone tracking from North America to the WNAO; (3) determine, by airstream, the slopes of the ozone/CO and ozone/NOy relationships; (4) determine the seasonal variation of airstream trace gas signatures between spring and late summer/early autumn. The results show that trace gas mixing ratios vary across airstreams, the product of air mass origin and evolution. Seasonality of photochemistry, cyclone tracks and stratosphere/troposphere exchange produced a seasonal variation of ozone and CO in all airstreams. The mean or median mixing ratio of an airstream trace gas is largely governed by airstream origin, and therefore these values vary according to cyclone path. However the linear relationship between two trace gases is proposed to be a more robust chemical signature of cyclone airstreams, and less influenced by the cyclone track. |
