Observed sea breeze life cycle in and around NYC: Impacts on UHI and ozone patterns

This observational study investigates New York City (NYC) impacts on summer sea breeze fronts (SBFs) during a 2018 LISTOS Campaign day with a regional heat wave and O-3 episode. A morning urban heat island peaked at 8.3 degrees C and then induced convergences into the City, trapping its NO2 emissions. SBFs came ashore at 0700 EST from the Atlantic along southern Long Island (LI), and from the LI Sound along northern LI and southern Connecticut; 2-h later another formed over New Jersey. The Ocean front was retarded over NYC at noon, while all fronts merged by 1400 EST and continued inland for four more hours. High O-3 first appeared at 0900 EST downwind of NYC. By 1100 EST, a new surface peak formed north of the City in the Hudson River Valley (HRV). The maxima merged, peaking at 143 ppb at 1300 EST behind the SBF and near the maximum temperatures of 39 degrees C. Trajectories ending at the northern LI site with a PBL O-3 peak first passed NYC, arrived before the episode, and then recirculated back in its SB flow. Trajectories ending in the HRV showed pollutant transport over NYC twice, before advection northward into the narrow Valley by the ocean SBF.