During TRACER-AQ, GCAS collected data over the Houston metropolitan area across 12 days during late Air mass factors use modeled scattering weights and vertical profile information to account for altitudedependent sensitivities in remote-sensing observations . The original vertical profiles in the dataset were derived from a global model, GEOS-CF , that had a coarser spatial resolution (0.25° × 0.25°), but in this study we only show GCAS column NO2 measurements processed with vertical profile information from CAMx. To directly compare GCAS measurements to the CAMx NO2 column concentrations we re-grid them to the fine-scale WRF-CAMx grid. Only cloud-free GCAS data is considered in this analysis. An example of daily and monthly averaged GCAS data is shown in Figure . The differences in these two timescales highlights the complexity of NO2 variance in cities, such as Houston. Diurnal column NO2 patterns are shown in Figure . and found minimal systematic biases in surface-level wind speed, direction, temperature, and water vapor mixing ratio compared to observations from sixteen ground-level monitors . A longer description of the WRF-CAMx model options is included in the supplemental including the WRF physics options (Table ), vertical layer mapping from WRF to CAMx (Table ), and CAMx science options (Table ). For emissions in CAMx, we start with an emissions inventory developed by the TCEQ for the Dallas-Fort Worth (DFW) and Houston-Galveston-Brazoria (HGB) Attainment Demonstration (AD) SIP revisions and implement further minor changes as discussed in the Supplemental.