THE ROLE OF ANTHROPOGENIC EMISSIONS OF NOX ON TROPOSPHERIC OZONE OVERTHE NORTH-ATLANTIC OCEAN - A 3-DIMENSIONAL, GLOBAL-MODEL STUDY

A three-dimensional, global tropospheric model is used to simulate the concentration of ozone over the North Atlantic Ocean over an annual c ycle. Two scenarios, a baseline and one in which North American fossil fuel NOx emissions are reduced 50% are simulated. The largest decreas es in O-3 are found in the summer months closest to the east coast of North America, presumably because of strong photochemical production a nd transport from the southwest due to the Bermuda High. Ozone decreas es are also predicted for other North Atlantic Ocean sites and occur t hroughout the year, but tend to be smaller than those off North Americ a. The total tropospheric mass of O-3 over a region from (2.2S, 82.5W) to (68.8N, 0) decreases by 1.8 Tg O-3 from 41.3 to 39.5 Tg O-3 when N orth American NOx fossil fuel emissions are reduced, or roughly 4.4%. Given recent estimates of the export of North American O-3 to the glob al atmosphere, the 50% fossil fuel NOx reduction corresponds to a 30% reduction in the total mass of tropospheric O-3 exported from North Am erica to the North Atlantic Ocean. Nonlinearities may be due to the fa ct that ozone production potential per unit NOx increases as NOx conce ntrations decrease.