Impacts of Bay Breezes and Deep Convective Circulations on Surface Ozone at Two Coastal Sites along the Chesapeake Bay

Coastal regions are frequently susceptible to high concentrations of ozone due to thermally-direct recirculation (e.g., bay breezes) of local pollutants during summer months. Along with high ozone concentrations on polluted days, the Chesapeake Bay breeze transports humid air over the land, which can lead to deep convection. These storms are triggered as a result of upward vertical transport of water vapor associated with the rising branch of the land-bay overturning circulation, as well as mesoscale frontal lifting and interactions with the synoptic-scale flow. While the bay breeze transports higher concentrations of ozone over land on polluted days, vertical transport by deep convection vents pollution out of the boundary layer, reducing ozone concentrations. The local net effect of these two mesoscale forcings (bay breezes and deep convection) on ozone concentrations has not been sufficiently quantified. Presented here is a bay breeze climatology at two Maryland coastal sites along the Chesapeake Bay from June, July, and August 2011-2016 during daylight hours. Using meteorological data from the Maryland Department of the Environment (MDE), bay breezes are identified by a detection algorithm, customized for the complex coastline of river inlets within the Chesapeake Bay area. Additionally, thunderstorm vs. non-thunderstorm days are also analyzed in the absence of synoptic fronts using gridded Earth Networks lightning data (ENTLN) within an influential radius of the two coastal sites. Using these detection techniques, the effects of bay breezes and deep convection on local exceedances of the 8-hr maximum ozone air quality standard will be quantified. These results demonstrate that localized meteorological events play a prominent role in air quality near bodies of water.