| In this study, the impact of winter-spring arctic outflow events on the budgets of tropospheric NOx and ozone over the North Atlantic Ocean is determined. An updated version of the NCAR Master Mechanism, a detailed, explicit photochemical model, is applied to trajectories representative of arctic outflow for the months of January through May. Revisions were made to the gas-phase mechanism in small increments to determine the effect of each set of revisions on simulated levels of NOx and O3. The effect of individual revision subsets had a much larger effect than the net result of all the revisions, as the revision subsets have opposing effects and counteract each other. The peroxy radical revisions had the largest effect on the level of NOx, increasing the average level by 24% over the original mechanism. For O3, the photolysis revisions had the largest effect, decreasing the net rate of ozone production by 0.5 ppb/day, a 49% reduction. Therefore, it is important that the impact of revisions to individual (or a family of) reactions are clearly understood, so that possible bias in calculated results can be avoided.; During simulations of arctic outflow, peroxyacetyl nitrate (PAN) mixing ratios drop by up to 270 pptv, increasing NOx levels up to 120 pptv. However, the released NOx is quickly destroyed by efficient NOx loss reactions leading to formation of HNO3 and, to a lesser extent, nitroaromatic compounds. As a result of elevated NOx O 3 levels are increased. The net impact resulting from elevated levels of PANs in the winter-spring Arctic on the budget of O3 over the North Atlantic is estimated to be less than 712 Gg O3/month. While this source is similar in magnitude to estimates of ozone produced from aircraft emissions, both are small in comparison to the export of ozone from North America. In conclusion, while elevated levels of pollutants in arctic outflow increase the levels of NOx and O3 in the North Atlantic region, on a seasonal basis the impact on the budgets of NOx and O3 in this region is small. |
