The advantage of a "top-down" technique is that it is independent of the complex datasets needed to estimate "bottom-up" emissions rates. Typically these aggregated "top-down" estimates agree with the "bottom-up" estimates within 40% in North American cities (well within the uncertainty associated with the 'top-down' method) . Given TROPOMI's spatial resolution (3.5 × 5.5 km 2 at nadir) and temporal resolution (once daily), TROPOMI is most often used to calculate total emissions aggregated over the entire metropolitan area and seasonal/annual timescales, and assumptions are needed to infer emissions rate during morning and evening hours. Therefore, very limited, if any, sectoral or hourly information can be gleaned from an analysis using polar-orbiting satellite datasets, such as TROPOMI.