Ozone pollution episodes and PBL height variation in the NYC urban and coastal areas during LISTOS 2019

In summer, frequent ozone (O3) episodes occur in New York City (NYC) and coastal areas along Long Island Sound (LIS) due to complex interplay of urban pollutants transport, land-sea breezes, and chemistry. The Long Island Sound Tropospheric Ozone Study (LISTOS) was carried out to address this issue; here we present an integrated analysis of the diurnal variation of planetary-boundary-layer height (PBLH) and O3 in the NYC urban and coastal area during LISTOS in summer 2019. A persistent O3 episode (July 28–31, 2019) is investigated which shows much higher O3 (90–120 ppb with 5-min average maximum) along the North-shore of Long Island (NLI) than the NYC urban and South-shore of Long Island (SLI). We evaluate the PBLH estimate with a multi-platform observation in the complex coastal environment, and compare the PBLH diurnal variation in the NYC urban to coastal areas. The results indicate lower PBLH in the mid-morning and noon in the NLI than the NYC urban area. With the simultaneously measured O3 and PBLH, the integrated O3 content or total content in the PBL defined as the O3 concentrations multiplying PBLH show good consistency in the urban and NLI coast at noon on July 28–29, 2019. A dense O3 plume, rich in CO, aerosols, black carbon, HCHO and NOx appeared in the PBL as detected from the UMD Cessna research aircraft, satellite TROPOMI and ozonesonde; their coincidently large values imply the combined impacts of urban plumes transport, lower PBLH and land-sea breezes in the NLI area. Finally, we evaluated the forecast of O3 and PBLH from the NOAA NAM-CMAQ (12 km grid) and WRF-Chem (1.3 km grid) models with the observations. Both models show good agreement with the observations at the NYC urban site; but at the NLI coastal site, the NAM-CMAQ model forecast indicates a timing bias for the maximum O3 at noon. These results provide insight into the impacts of the sea breeze and urban heat island on air quality.