The first part of the research will focus on nitrogen dioxide (NO 2) since this molecule has a long history of measurements from satellites (Monks and Beirle, 2011, Martin, 2008) due to its relative abundance in the lower troposphere. NO2 satellite measurements have always been from low-earth orbiting satellites taken at approximately the same local time (Martin, 2008). In reality, the observed distribution of this trace gas is a result of several processes that are both temporally dependent through the course of the day and spatially dependent on scales of several km. Emissions from traffic have a characteristic temporal pattern along roadways that is sensitive to rush hour inputs. In addition, as these emissions are put into the atmosphere, there is a temporal dependence on the chemistry that is driven by the diurnal nature of atmospheric photochemistry. Once these functions of time-dependent factors are taken into account, the transport of these quantities are impacted by the meteorology of the region, which redistributes all the trace gases. The net result is that the observed distribution in a specific region is determined from a complex interaction of emissions, chemistry and meteorology.

We incorporate all of the above factors to investigate NO2 concentrations at the surface and calculated NO2 column amounts. The NO2 column amount is the quantity that is measured by spaceborne instruments. This study examines the differences in the resultant spatial gradients of both the surface and integrated quantities in the greater St. Louis metropolitan area. To accomplish this goal the following research steps have been completed: • The Community Air Quality with Extensions (CAMx) model is used to simulate ozone and NO2 at a 4 and 12 km resolution over the St. Louis metropolitan area. • Integrated gas column and surface concentration relationships are derived to better understand the... • Performed a specific case study analysis to see if a localized air pollution event seen on July 2, 2012 can be simulated by CAMx and whether or not such an event could be detected by an instrument such as TEMPO. • Developed a high spatial and temporal emissions data base for St. Louis -- this work has been done independently using MOVES2014 (Motor Vehicle Emissions Simulator).

Also, we compare our model results with surface ozone measurement observations. In general, both the model-derived results and observations are in reasonably good agreement during the 5-day simulation period that is presented here.

We also examined the temporal surface distribution of these trace gases in the St. Louis Metropolitan area. One purpose of this research is to provide some insight into the diurnal cycle that can be expected for the integrated column amounts throughout the course of the day because TEMPO will be the first instrument to make measurements throughout the day.