To study the impact of air pollution from North America on the composition of the marine troposphere over the North Atlantic Ocean (NAO), we have undertaken chemical transport model calculations for the period of the AEROCE (Atmosphere/Ocean Chemistry Experiment) intensive in the Spring of 1996. The goal of this intensive was to differentiate between natural and anthropogenic ozone over the NAO. From March 29 to May 3, trace gas and aerosol measurements were performed during research flights over eastern North America and over the NAO between the U.S and Bermuda. Surface measurements also took place at Bermuda during the intensive.
The first step in this modeling analysis is to assess the model's ability to tranport ozone precursors from North America to the NAO.
We use the Stretched-grid version of the Goddard Chemical Transport Model (SG-GCTM), which uses data from the 46-layer version of the Goddard Earth Observing System data assimilation system (GEOS-STRAT DAS). The model's ability to simulate transport in this region and time period is evaluated by performing Rn-222 simulations and comparing to surface measurements at Bermuda. Preliminary results from CO and NOy calculations using detailed CO and NOx emissions over eastern North America are also shown. Simple parametrized chemistry is used for CO. NOy is assumed to be "Radon like" with a lifetime of a few days to account for HNO3 scavenging by precipitation. Model calculated mixing ratios are compared with aircraft and surface observations at or near Bermuda. The study will focus on the episode on April 28, where convective activity ahead of a cold front over the U.S Midwest, followed by transport, led to pollutant levels typical of the rural U.S in the lower to mid-troposphere near Bermuda.
Symposium on Interdisciplinary Issues in Atmospheric Chemistry