Studying the Interrelationships between Urban Tropospheric NO2 and Downwelling Radiation on Ozone and Aerosol Formation.

In this paper, we focus on exploring the statistical connections between high NO2 and concentration levels and resultant downwind O3 over the Long Island Sound and Connecticut for a 4 month period from July 2018 to Oct 2018. To begin this study, we make use of tropospheric NO2 concentrations obtained from the NASA Pandora network to quantify NO2 concentrations that are integrated from sunrise to different times during the day. In order to make sure that the integrated quantities are dominated by non-local sources, we used 2 neighboring Pandora sites and used coincidence filters to ensure that only cases where both instruments are similar are used. At the same time, we also used the GOES-16 ABI downwelling Solar Irradiance product to quantify the time integrated solar irradiant flux to ensure high photochemical reactions over the morning period. Further, we made use wind trajectories from Hysplit to filter cases where the transport from NYC to the Long Island Sound / New Haven CT were efficient and use the O3 lidar facilities at New Haven CT to quantify the total tropospheric O3 levels. Based on initial analysis, we see fairly significant correlation to high O3 levels when both the Solar Irradiation flus and NO2 flux levels are high when the HONO levels are sufficiently high so we are likely in a NOx limited range wjhere NO2 / O3 sensitivity is largest. In measuring HONO levels, we make use of TROPOMI retreivals which unfortunately are very noisy. However, if we perform a suitable spatial / temporal averaging, we can isolate specific high level cases which signal NOx saturation conditions.

In addition to the connections between NO2 and O3, we also explore the diurnal behavior of aerosols in relation to the NO2 / radiation diurnal patterns using the GOES 16 AOD retrieval products using optimized temporal aggregation to provide the best accuracy and coverage. Studies with multiple AERONETS will be used to assess the errors associated with the retrievals. Besides statistical assessments, we will explore a number of heat wave cases as well including an assessment of NO2 as a function of the difference in NOx emissions between weekday and weekend cases. We will illustrate sharp changes in NO2 levels as the interface between weekday and weekend and assess whether these mechanisms can be observed with TROPOMI and/or TEMPO

Attempts to derive quantitative metrics for this process will be discussed.