Deriving CO2 emissions of localized sources from OCO-3 XCO2 and TROPOMI NO2 satellite data

Carbon dioxide (CO₂) is the most important anthropogenic greenhouse gas and the main driver of global warming. Its atmospheric concentrations have risen more than 40% since pre-industrial times. Almost 90% of this increase results from fossil fuel combustion, emitting CO₂ predominantly from localized sources. In order to track the reduction efforts to comply with the objectives of the Paris Agreement, emissions need to be monitored. For this purpose, bottom-up emission estimates are regularly reported in the national greenhouse gas inventories. Top-down observation-based estimates can complement and verify these inventories. Satellite observations have an important role in this context, since they can provide global information.

Due to CO₂'s long lifetime and large fluxes of natural origin, the column-average concentrations resulting from anthropogenic emissions from individual source points are usually small compared to the background concentration, and these enhancements are often barely larger than the satellite's instrument noise. This makes the detection of CO₂ emission plumes and the quantification of anthropogenic fluxes challenging.

NO₂ is co-emitted with CO₂ in the combustion of fossil fuels. It has a much shorter lifetime, and as a result, its vertical column densities can exceed background values and sensor noise by orders of magnitude in emission plumes. This makes it a suitable tracer for recently emitted CO₂.

The objective of this study is to quantify the CO₂ emissions from localized sources such as power plants by using XCO₂ (the column-averaged dry air mole fraction of CO₂) retrievals from the Orbiting Carbon Observatory 3 (OCO-3) in its snapshot area mode. Our presentation describes a plume detection method using NO₂ as a tracer for recently emitted CO₂ and an inversion technique to quantify CO₂ emissions from detected CO₂ plumes.