A MODELING STUDY OF TROPOSPHERIC SPECIES DURING THE NORTH-ATLANTIC REGIONAL EXPERIMENT (NARE)

A three-dimensional regional chemistry model is used to simulate distr ibutions of a number of tropospheric species over eastern North Americ a and the western North Atlantic for August of 1993. The model is test ed by comparisons of the results with observations obtained at two gro und stations in Nova Scotia, Canada, and on board two aircraft. The mo deled mixing ratios of CO and O-3 as well as the ratio of Delta O-3/De lta CO at the two ground sites are in satisfactory agreement with the observations. More than 90% of the aircraft-observed O-3 and CO and 75 % of NOy can be reproduced by the model with relative differences less than 50 and 100%, respectively. The model-simulated correlations amon g O-3, CO, and NOy are dose to the aircraft observations. Most of the model-calculated vertical distributions of these species have the same pattern as the observations. The calculated profiles coincide with th e observations with mean discrepancies of about 25, 30, and 100% for O -3, CO, and NOy, respectively. The model-calculated wind speeds are in good agreement with the observations. Continental plumes within the m odel may be spatially off by a few hundred kilometers or temporally of f by several hours. Possible inaccuracy in side boundary conditions an d some difficulties in capturing small scale processes like small scal e intrusion from the stratosphere and subgrid scale convective mixing are possible explanations for discrepancies between chemical data and model results.