This book is to facilitate interactions among researchers in the key areas of field measurements, laboratory studies and modeling who have experience in air chemistry of the continental lower troposphere, the stratosphere and its polar regions. These interactions have become increasingly important since it is apparent that the arctic troposphere plays an important role in environmental concerns with respect to global change. It is a unique chemical reactor influenced by human activity and the Arctic Ocean. In winter industrialized continents contribute gaseous and particulate pollution. It is underlain by the flat Arctic Ocean from which it is separated by a crack-ridden ice membrane 3-4 m thick. Ocean to atmosphere exchange of heat, water vapor and marine biogenic gases influence the composition of the reactor.