(Invited Presentation) Short-lived organic trace gases in the remote atmosphere: Results from recent field campaigns

The trace gas composition of the upper troposphere/lower stratosphere (UT/LS) region depends on emission sources, transport pathways, mixing rates and photochemical processing time. Because surface emissions include gases with a range of chemical lifetimes, and because different source emissions (e.g. marine boundary layer, anthropogenic emissions, biomass burning) can have different chemical signatures, the composition of the organic trace gases that are found in the UT/LS and throughout the remote atmosphere have the potential to provide diagnostic information on air mass sources and transport time scales. For most reactive organic halogen compounds, such as bromoform, air-sea exchange is a major source to the atmosphere. Measurements of this flux provide the boundary conditions to evaluate the potential impact of reactive halogen on the chemistry of the UT/LS region. In fact, measurement of short-lived organic halogen gases in the UT/LS provides data to define the reactive halogen budget and the chemical boundary conditions for the stratospheric chemistry that affects ozone depletion rates. Recent airborne and ship-based research campaigns in the tropics, the extra-tropics, and in mid-ocean transects, from near surface to the lower stratosphere have included the measurement of a wide range of trace gases including halocarbons, hydrocarbons, and related species. This presentation will emphasize short-lived trace gases and will highlight different aspects of these measurements that deal with distributions, seasonality, transport pathways, transport rates, and halogen budgets.