Analysis of NO2 and O3 variation in 2020 and 2021 and application to evaluate the GFS-CMAQ model forecast in New York city 

<p>The US National Ambient Air Quality Standard (NAAQS) dictates the limits on atmospheric pollutants, including the tropospheric ozone (O₃). Its exceedance of the limit typically happens in the summer because of changes in meteorology, chemistry, and emissions. Since O₃ affects pulmonary function and has been linked to higher risks of depression and anxiety diagnoses, it is essential to understand O₃ and its precursor nitrogen dioxide (NO₂) variations. In July 2021, the Finite Volume Cube-Sphere Dynamic Core in Global Forecasting System (FV3-based GFS) became the new meteorological driver coupled with the Environmental Protection Agency&#8217;s Community Multiscale Air Quality System (CMAQ). Together they make up the National Air Quality Forecasting Capability (NAQFC), which provides hourly forecasts of a variety of atmospheric species and meteorological fields. Therefore, it is necessary to evaluate the model&#8217;s output relevant to O₃ production in an urban environment and investigate potential biases.</p><p>This study uses integrated remote sensing from a ceilometer, a wind LIDAR, the PANDORA spectrometer, and satellite Sentinel-5, and surface observations to investigate the spatial and temporal variability of NO₂, O₃, and planetary-boundary-layer height (PBLH) in August 2020 and 2021.</p><p>At first, surface-level and column NO₂ was observed from the co-located in-situ samplers and the PANDORA spectrometers at City College of New York (CCNY) and Queens College (QC) sites in New York City area. Then, the NO₂ and O₃ temporal variations at the two sites were compared and indicated a strong correlation for O₃ and a moderate correlation for NO₂. Meanwhile, the TROPOMI observations show spatial variation of tropospheric column NO₂.</p><p>The performance of the model&#8217;s product was evaluated using integrated observations and showed to be in good agreement with observations for the surface O₃ at the two sites for the month of August 2020. For the surface NO₂, the model forecast product generally showed similar diurnal variation but over-predicted the peak values likely related to complex urban emission sources and NO₂ vertical mixing in the PBL. The correlation analysis of the model and observation data over weekdays and weekends were conducted that demonstrated the increased emission effects from the vehicular traffic during weekdays. The O₃-NO₂ titration from the model showed good consistency with the observations. Additionally, O₃-NO₂ variations from the month of August 2021 were evaluated and compared against the levels in 2020.</p>