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The Arctic troposphere (0 to ca. 8 km) plays an important role in environmental concerns for global change. It is a unique chemical reactor influenced by human activity and the Arctic ocean. It is surrounded by industrialized continents that in winter contribute gaseous and particulate pollution (Arctic haze). It is underlain by the flat Arctic ocean from which it is separated by a crack-ridden ice membrane 3 to 4 m thick. Ocean to atmosphere exchange of heat, water vapor and marine biogenic gases influence the composition of the reactor. From September 21 to December 21 to March 21, the region north of the Arctic circle goes from a completely sunlit situation to a completely dark one and then back to light. At the same time the lower troposphere is stably stratified. This hinders vertical mixing. During this light period, surface temperature reaches as low as -40°C. In this environment, chemical reactions involving sunlight are generally much slower than further south. Thus, the abundance of photochemically reactive compounds in the atmosphere can be high prior to polar sunrise. Between complete dark in February and complete light in April, a number of chemical changes in the lower troposphere take place.
List of contents
Section I: Overview.- Features of Polar Regions Relevant to Tropospheric Ozone Chemistry.- Climatology of Arctic and Antarctic Tropospheric Ozone.- Polar Sunrise Studies.- Section II: Tropospheric Oxidants Modelling.- Meteorology and Transport of Air Masses in Arctic Regions.- Impact of Global NOx Sources on the Northern Latitudes.- Ozone Depletion During Polar Sunrise.- Section III: Field Studies.- Relationship Between Anthropogenic Nitrogen Oxides and Ozone Trends in the Arctic Troposphere.- Halocarbons in the Arctic and Antarctic Atmosphere.- Measurements of Hydrocarbons in Polar Maritime Air Masses.- Carbon Monoxide and Light Alkanes as Tropospheric Tracers of Anthropogenic Ozone.- Atmospheric Distribution of NO, O3, CO, and CH4 above the North Atlantic Based on the STRATOZ III Flight.- Spectroscopic Measurement of Bromine, Oxide, Ozone, and Nitrous Acid in Alert.- Ice Core Analysis in Arctic and Antarctic Regions.- Record of Atmospheric Oxidant from Polar Ice Cores Over the past 100,000 Years: Dream or Real Possibility?.- Section V: Marine Sources and Sinks.- Sources of Organobromines to the Arctic Atmosphere.- Hydrocarbons Emission from the Ocean.- Cycle of Tropospheric Phosgene.- Session VI: Laboratory Studies of Heterogeneous Reactions.- Chemical Interactions of Tropospheric Halogens on Snow/Ice.- Reactions of Halogens Species on Ice Surfaces.- Heterogeneous Reactions of Chlorine Compounds.- Liquid Phase Photochemistry in Relation to Tropospheric Chemistry of Halogens.- Session VII: Homogeneous Gas-phase Reactions.- Ozone HOx Photochemistry in the Troposphere - Latitudinal Dependence of Reaction Rates.- ClO + ClO ? Products: A Case Study in Halogen Monoxide Disproportionation and Recombination Reactions.- Thermal Stability of Peroxynitrates.- TemperatureDependence (256-296 K) of the Absorption Cross Sections of Bromoform in the Wavelength Range 285-360 nm.- Oxidation of Organic Sulfur Compounds.- Halogen and Sulfur Reactions Relevant to Polar Chemistry.- Reactions of BrO Radicals Relevant to Polar Chemistry.- Comparative Assessment of the Role of Iodine Photochemistry in Tropospheric Ozone Depletion.
