EGU2020-11042
https://doi.org/10.5194/egusphere-egu2020-11042
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Quantifying NOx emissions from a city and a small country with the TROPOMI and OMI satellite instruments

Folkert Boersma1,2, Marina Zara1,2, Alba Lorente1,3, Henk Eskes2, and Maarten Krol1
Folkert Boersma et al.
  • 1Wageningen University, Meteorology and Air Quality group, Wageningen, Netherlands (folkert.boersma@wur.nl)
  • 2KNMI, Satellite Observations Department, De Bilt, Netherlands
  • 3SRON, Netherlands Institute for Space Research, Utrecht, Netherlands

The TROPOMI and OMI satellite sensors provide an exciting perspective on the sources, dispersion, and fate of air pollution, and in particular on nitrogen dioxide (NO2). Yet it is still difficult to relate satellite observations of tropospheric NO2 columns to the underlying NOx emissions and their trends. Robust interpretation of satellite data relies on a good understanding of the accuracy and representativeness of the satellite data itself, but also on the relationship between NOx emissions and the observable NO2 amount. This relationship is influences by local chemistry, mixing and dispersion, and by the NO2 amount in the free troposphere. We address these issues via two examples:

(1) Direct estimation of NOx emissions from the satellite-observed build-up of pollution over the city of Paris. After validating NO2 measurements from TROPOMI over the heart of Paris, we analyse the observed build-up of NO2 pollution over the city along with the wind. Over the city, recently emitted NOx has been oxidized to limited degree, facilitating the use of TROPOMI data to directly determine the strength and distribution of emissions from the city. From the observed build-up of NO2 pollution, we find highest NOx emissions on cold weekdays in February 2018, and lowest emissions on warm weekend days in spring 2018.

(2) Trends in NO2 over The Netherlands. We use the QA4ECV OMI NO2 record to investigate trends in tropospheric NO2 columns over Europe, and in particular over The Netherlands between 2005 and 2018. In spite of the differences in metrics and sampling techniques, the NO2 measured in the Dutch atmosphere from space and from the ground follows a trend that is consistent with predictions by emission inventories. Surface NO2 is reduced by 32% in 2018 relative to 2005, OMI NO2 by 35%, and NOx emissions by 32%-38% depending on the inventory. Interestingly, the Dutch surface concentrations reveal an upward trend in the NO2:NO ratio in line with O3 increases. This suggests that the NO2 makes up an increasing share of the NOx in the lower atmosphere as NOx emissions decline. This needs to be accounted for when interpreting NO2 trends as proxy for NOx trends.

How to cite: Boersma, F., Zara, M., Lorente, A., Eskes, H., and Krol, M.: Quantifying NOx emissions from a city and a small country with the TROPOMI and OMI satellite instruments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11042, https://doi.org/10.5194/egusphere-egu2020-11042, 2020