The impact of increased ship emissions on nitrate radicals at low irradiation

In the Arctic and subarctic air pollution is processed differently from the more studied mid- latitudes because of the unique environmental conditions (cold, long dark nights, presence of inversions, snow and ice). WRF/Chem is applied to examine how the increase in NO_x emissions between 1990 and 2000 affects NO_x, NO_y, NO_z and O_x. A major increase of NO_x emission results from the increasing ship traffic. During the long dark Alaskan nights, NO₂ reacts with the available ozone to NO₃, which then can react with NO2 to N2O5. These nocturnal intermediates (NO₃, N₂O₅) control the NO_x concentrations. N₂O₅ is removed by clouds. Preliminary results also show that the amount of NO₃ built decreases as the length of day increases and from north to south. The frequent Aleutian Lows take up the pollution emitted along the sea-routes and transport it into the Alaska coastal regions. In the discussion, focus will be on differences as compared to mid-latitude ship emission impacts in behavior of chemical processes during the long white nights and dark days of Alaska.