Top-down NOx emissions

The recent launch of geostationary (GEO) platforms such as the Tropospheric Emissions: Monitoring of Pollution (TEMPO) offer an unprecedented opportunity to better monitor the harmful air pollutant nitrogen dioxide (NO2) due to their revolutionary high spatiotemporal resolution. We investigate the benefit of using TEMPO (GEO) NO2 data for NOxemissions estimates compared to the low-earth orbit (LEO) instrument TROPOspheric Monitoring Instrument (TROPOMI). Top-down NOx emissions derived from midday TEMPO and TROPOMI data during August 2023 were similar over urban regions, both reducing the bottom-up NOx emissions obtained from 2021 GReenhouse gas And Air Pollutants Emissions System (GRA2PES) by 5-20%. Top-down emissions estimates were found to have better agreement with newer (2023) GRA2PES emissions, demonstrating the capability of using satellite data for timely updates of bottom-up inventories. The satellite-derived NOx emissions also improve NOx and ozone simulations, especially when TEMPO data are used. Our study indicates that TEMPO midday data can better track and infer NOx sources than TROPOMI's once-daily measurements. This study demonstrates the value of GEO data in the application of emissions estimates and air quality forecasting, underscoring the value of future GEO satellite platforms for monitoring atmospheric composition.The satellite- derivedNOx emissions in this study are available on CU Boulder’s online repository.