Performance Evaluation of the Meteorology and Air Quality Conditions From Multiscale WRF‐CMAQ Simulations for the Long Island Sound Tropospheric Ozone Study (LISTOS).

The Long Island Sound (LIS) Tropospheric Ozone Study was a multi‐agency collaborative field campaign conducted during the summer of 2018 to improve the understanding of ozone chemistry and transport from New York City to areas downstream, especially the LIS and adjacent Connecticut coastline. Measurements made during this campaign were leveraged to test and evaluate the coupled WRF‐CMAQ model at 12 km, 4 and 1.33 km horizontal grid spacing. Special attention was placed on the model's representation of sea breeze circulations, low level jets, and boundary layer evolution. The evaluation suggests using higher resolutions resulted in improved surface meteorology statistics throughout the whole summer, with temperature biases seeing the biggest statistical improvements when using 1.33‐km grid spacing, going from −0.12 to 0.08 K. Additionally, 4‐km grid spacing provided the biggest advantage when simulating ozone over the region of interest, with biases being reduced from 2.40 to 0.57 to 0.37 ppbV with increased resolution. Case studies of two high ozone concentration events (July 10 and August 6) revealed that sound breezes and low‐level jets had a critical role in transporting pollutant‐rich, shallow marine air masses from the LIS inland over the Connecticut coast. Modifications were made to the representation of sea surface temperatures, which subsequently improved the simulation of surface ozone predictions. Plain Language Summary: Surface‐level ozone pollution across the country is closely monitored by the U.S. Environmental Protection Agency due to the threat it can pose to public health and safety. Ozone is not emitted naturally; instead it forms when other pollutants are emitted and exposed to sunlight. Ozone pollution can be especially harmful near large urban areas like New York City where high emissions of pollutants and local meteorology interact to produce ozone within the city and transport it downwind across the Long Island Sound into Connecticut. In this study, we used a weather and chemistry model to explore how surface winds over the LIS impact high ozone along the Connecticut and Long Island coastlines. Our work highlighted the importance of accurately modeling meteorological conditions so that we can adequately represent high ozone events in models. We also found that ozone over Connecticut is especially sensitive to where and when local wind features like sound breezes and low‐level jets form and dissipate. Continued work in these areas of study can help policy makers develop strategies that control all the factors that cause ozone pollution in this area. Key Points: High‐res WRF‐CMAQ model simulations showed improvements to surface meteorology and ozone over the NYC‐Connecticut‐Long Island Sound regionSound breezes along the CT and Long Island coasts were found to be instrumental to the modeled transport of ozone and its precursorsIncorporating diurnal variations to sea surface temperatures improved the representation of transport and surface ozone mixing ratios [ABSTRACT FROM AUTHOR]