Abstract
This study investigates the use of co-located nitrogen dioxide (NO2) and carbon monoxide (CO) retrievals from the TROPOMI satellite to improve the quantification of burning efficiency and emission factors (EFs) over the megacities of Tehran, Mexico City, Cairo, Riyadh, Lahore, and Los Angeles. Efficient combustion is characterized by high NOx (NOCNO2) and low CO emissions, making the NO2=CO ratio a useful proxy for combustion efficiency (CE). The local enhancement of CO and NO2 above megacities is well captured by TROPOMI at short averaging times compared with previous satellite missions. In this study, the upwind background and plume rotation methods are used to investigate the accuracy of satellitederived 1NO2=1CO ratios. The column enhancement ratios derived using these two methods vary by 5% to 20% across the selected megacities. TROPOMI-derived column enhancement ratios are compared with emission ratios from the EDGAR v4.3.2 (Emission Database for Global Atmospheric Research v4.3.2) and the MACCity (Monitoring Atmospheric Chemistry and Climate and CityZen) 2018 emission inventories. TROPOMI correlates strongly (r D 0:85 and 0.7) with EDGAR and MACCity, showing the highest emission ratio for Riyadh and lowest emission ratio for Lahore. However, inventory-derived emission ratios are 60% to 85% higher than TROPOMI column enhancement ratios across the six megacities. The short lifetime of NO2 and the different vertical sensitivity of TROPOMI NO2 and CO explain most of this difference. We present a method to translate TROPOMI-retrieved column enhancement ratios into corresponding emission ratios, thereby accounting for these influences. Except for Los Angeles and Lahore, TROPOMI-derived emission ratios are close (within 10% to 25 %) to MACCity values. For EDGAR, however, emission ratios are 65% higher for Cairo and 35% higher for Riyadh. For Los Angeles, EDGAR and MACCity are a factor of 2 and 3 higher than TROPOMI respectively. The air quality monitoring networks in Los Angeles and Mexico City are used to validate the use of TROPOMI. For Mexico City and Los Angeles, these measurements are consistent with TROPOMI-derived emission ratios, demonstrating the potential of TROPOMI with respect to monitoring burning efficiency.
| Original language | English |
|---|---|
| Pages (from-to) | 10295-10310 |
| Number of pages | 16 |
| Journal | Atmospheric Chemistry and Physics |
| Volume | 20 |
| Issue number | 17 |
| Early online date | 4 Sept 2020 |
| DOIs | |
| Publication status | Published - 2020 |
Funding
Financial support. This research has been supported by the NWO Acknowledgements. We would like to thank the team that realized the TROPOMI instrument, consisting of the partnership between Airbus Defence and Space Netherlands, KNMI, SRON, and TNO, commissioned by NSO and ESA. Sentinel-5 Precursor is part of the EU Copernicus programme, and Copernicus Sentinel data for 2018 were used in this study. This research is funded by the NWO GO programme (grant no. 2017.036). We thank Tobias Borsdorff and Alba Lorente for providing the modified Copernicus Sentinel data 2018 CO data. Tobias Borsdorff and Alba Lorente are funded by the TROPOMI national programme through NSO. We are grateful to SURFSara for making the Cartesius HPC platform available for computations via computing grant no. 17235. We would also like to thank the South Coast Air Quality Management District (AQMD) monitoring network and Calidad del aire for the free use of air quality data.
| Funders | Funder number |
|---|---|
| Nederlandse Organisatie voor Wetenschappelijk Onderzoek | 17235, 2017.036 |
