Investigating Impacts of Local Circulation on Coastal Ozone Problem in the New York Metropolitan Area

Elevated surface ozone levels are often detected during hot summer days in the New York metropolitan area, including New York City (NYC), Long Island (LI), the south shore of Connecticut (CT), and the northeast corner of New Jersey (NJ), due to the rich sources of local anthropogenic and natural ozone precursor emissions. Moreover, surface ozone in this region exhibits extensive horizontal and vertical gradients and distinctive diurnal cycles when coupled with transport by complex boundary layer circulation induced by the intricate coastal geometry throughout the domain. This study first examines the spatial and temporal ozone characteristics under different cluster-based local circulation scenarios during summertime in the pre-COVID era of 2017-2019, utilizing observations from various surface networks, New York State Mesonet (NYSM) Profilers, and 2018 Long Island Sound Tropospheric Ozone Study (LISTOS), as well as composites from the High-Resolution Rapid Refresh (HRRR) reanalysis fields and National Emission Inventory (NEI). The most polluted days are closely associated with classic sea breeze days with weak large-scale flow. When sea breeze development in the New York Bight is delayed, and its penetration into the NYC and shores of western Long Island Sound is intercepted by the dominant westerlies, daily 8-hr maximum average ozone (DMA8) in the hot spots of NYC and south shore of CT would drop more than 10 ppb under comparable temperature levels. The probability of DMA8 exceeding the Ozone National Ambient Air Quality Standards (NAAQS) level of 70 ppb is also dramatically decreased. Furthermore, meteorological characteristics, such as sea breeze onset time and strength, most critical to ozone exceedances and high peaks are identified and analyzed for future improvement in coastal ozone simulation and prediction.