Assessing the Capability of Sentinel-5P (TROPOMI) NO2 Measurements to Monitor Point Source CO2 Emissions

Monitoring greenhouse gas (GHG) emissions is crucial for mitigating global warming and the associated climate change. Various satellite missions are dedicated to measuring CO₂ globally, demonstrating their capability to detect GHG emission hotspots and quantify emissions effectively. However, due to the limited revisit frequency and spatial coverage of contemporary high-resolution CO₂ monitoring missions such as OCO-2 and OCO-3, continuous daily monitoring of CO₂ emissions from specific sources remains challenging. To overcome these limitations, combining data from different satellite missions is a promising approach. Missions such as TROPOMI provide daily monitoring of various trace gas concentrations (e.g., NO₂, CO, SO₂). 

CO₂ is emitted from sources along with other species, such as CO and NO₂. Therefore, it is possible to infer CO₂ emissions from the emissions of co-emitted species. Compared to other co-emitted species, NO₂ has a relatively short lifetime of a few hours to a day, which makes it easier to distinguish enhancements from background concentrations.

Individual power plant CO₂ emissions are not reported in many parts of the world. Some countries, such as India, have started reporting daily coal consumption data for individual power plants since 2022. The amount of coal consumed can be used to estimate CO₂ emissions due to its strong linear correlation with CO₂ emissions. To overcome the limitations in reporting CO₂ emissions from power plants globally, we evaluate the potential of TROPOMI NO₂ measurements for monitoring CO₂ emissions. This is achieved by comparing the derived daily NO₂ emissions with the daily coal consumption of individual power plants in India.

A Gaussian plume (GP) model accounting for NO₂ lifetime was used to estimate the daily NO₂ emissions along with the NO₂ lifetime. In our study, we also attempted to address a key issue found in previous literature: the presence of an additional emission source downwind of the main source can render both NO₂ emission estimates and NO₂ lifetime estimates unreliable. We address this issue by simultaneously modeling and fitting the NO₂ emissions and NO₂ lifetime of the additional source, in conjunction with the main power plant GP inversion framework.

Our findings show a moderate to good linear relationship between daily NO₂ emissions and daily coal consumption of individual power plants. This suggests that TROPOMI NO₂ measurements can effectively support the monitoring of CO₂ emissions. Finally, this study highlights that upcoming satellite missions monitoring NO₂ can be used, along with GHG satellite measurements, for regular monitoring of carbon emissions.