Exploring the spatial and temporal signatures of TROPOMI measured NO2 plumes over NYC

In this paper, we study the spatial and temporal properties of TROPOMI measured tropospheric NO2 plumes extending earlier comparisons made specifically for the LISTOS (Long Island Sound Tropospheric Ozone Study) campaign in July 2018 to a 4 month period extending from July 2018 - Oct 2018. To begin, we provide extended Calibration and validation of the NO2 TROPOMI concentration retrievals using multiple NASA PANDORA instruments and explore the biases and RMSE differences as a function of the temporal window averaging of PANDORA. These comparisons show that validations require significant time averaging to account for the rapid space time variability of urban NO2 concentrations.

In a complementary study, we also used TROPOMI NO2 concentration fields to explore the connection between the extent of the NO2 plumes observed and time integrated horizontal wind fields from the NRRR 3km model. Besides using specific case examples where the time integrated boundary layer winds affected the spatial extent of the plumes, we also explored this phenomenon statistically. The statistical study explored how well the magnitude of the dispersion of the NO2 plume correlated with wind speed magnitude integrated over different time intervals of the day. These studies showed the importance of not just using the instantaneous wind fields but require taking into account the behavior of the wind fields over the day. We also showed the importance of re-projection of the plume field onto an axis oriented along the wind field and correlating the wind field to the projected plume dimensions.

We also focused on exploring the the time signature of the TROPOMI NO2 concentrations in comparison to the NEI emission inventories with special attention to observing the potential differences seen between weekday and weekends when NEI's can double.We find that such signatures can be seen under specific stagnant heat wave conditions but can other wise be averaged out.