Atmospheric measurements are needed to constrain bottom-up inventories of greenhouse gases. In particular, anthropogenic emissions of carbon monoxide (CO) and methane (CH4) are thought to be underestimated in many cities by globally gridded emission inventories. The Tropospheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite provides unprecedented spatial resolution of these trace gases at a daily (or better) revisit rate. Measurements of CO and CH4 are combined with measurements of nitrogen dioxide (NO2) from TROPOMI and carbon dioxide (CO2) from the Orbiting Carbon Observatory 2/3 using the enhancement ratio technique. This is an entirely data-driven technique that avoids the complexity of transport modelling. Co-located total column enhancements are calculated over a city relative to clean background values, then enhancements of one trace gas are fit onto another. These enhancement ratios are compared to various globally gridded and city-specific inventories. Enhancement ratios (e.g. CO:CO2) can also be combined with inventory emissions of one trace gas (CO2) to calculate emissions of the other trace gas (CO). Additionally, I will discuss the potential integration of an alternative CO and CH4 data product into this research. And I will introduce my new methodology for calculating seasonal enhancement ratios by rotating and oversampling many TROPOMI overpasses.