Low-altitude ozone concentrations over southwestern Nova Scotia: Meteorological factors and model sensitivity

Data analyzed from tethersonde flights over Chebogue Point, Nova Scotia (44°N, 66°W) and from the Scotia Prince ferry which crosses the Gulf of Maine reveal the complex structure of ozone in the vertical and the impact that temperature and wind have on this structure. The characteristics are further complicated by the cold sea temperatures adjacent to this location which results in a shallow stable layer forming near the coast. The Canadian Hemispheric Ozone and NOx System (CHRONOS) chemical transport model generally displays a positive bias in predicting ozone concentrations at and near the ground level at this coastal location. Sensitivity studies on the ozone deposition velocity and the impact of the recent correction to the point source emissions fields were conducted to test the model response. The significance of improving the vertical resolution of the meteorological driving model in representing the thermal internal boundary layer and thereby improving ground-level ozone prediction is highlighted.