Quantifying burning efficiency in Megacities using NO2/CO ratio from the Tropospheric Monitoring Instrument (TROPOMI)
Abstract
Economic development and rapid urbanization have increased the consumption of fossil fuel in megacities degrading the local air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. It varies with environmental conditions and influences the ratio at which pollutants are emitted, as expressed by the emission factor. Emission factors are an important source of uncertainty in global emission inventories. To improve the quantification of burning efficiency and emission factors, this study investigates co-located NO2 and CO satellite retrievals from TROPOMI over the megacities of Tehran, Mexico City, Cairo, Riyadh, Lahore and Los Angeles. The TROPOMI instrument was successfully launched by the European Space Agency on 13 October, 2017. It measures atmospheric trace gases with daily coverage and a spatial resolution of 7x7 km2. At this resolution, TROPOMI detects hotspots of CO and NO2 pollution over megacities in single satellite overpasses. The Upwind Background and Plume rotation methods are applied to quantify and evaluate TROPOMI derived ∆NO2/∆CO ratios. TROPOMI derived ∆NO2/∆CO ratios show a strong correlation (r = 0.85 and 0.7) with emission ratios from the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) and Monitoring Atmospheric Chemistry and Climate and CityZen (MACCity) 2018, with the highest ratio for Riyadh and lowest for Lahore. Inventory-derived emission ratios are larger than TROPOMI-derived total column ratios by 60 to 80%. As we will show, this can largely be explained by the limited lifetime of NO2 and the different vertical sensitivity of the TROPOMI NO2 and CO column retrievals. Taking this into account, TROPOMI retrieved emission ratios are generally within 10 to 25% of MACCity. However, larger differences, up to 80%, are found with EDGAR. For Los Angeles, both inventories overestimate NO2/CO ratios compared with TROPOMI. Validation using the air quality monitoring network of Los Angeles supports the lower ∆NO2/∆CO ratios inferred from TROPOMI, indicating that burning efficiencies in Los Angeles are indeed poorer than indicated by the inventories.
Authors 9
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Srijana Lama corresponding
Affiliation as printed
Vrije University of Amsterdan , Earth Science, Netherlands (s.lama@vu.nl)
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Space Research Organisation Netherlands · Vrije Universiteit Amsterdam
Affiliation as printed
SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
Vrije University of Amsterdan , Earth Science, Netherlands (s.lama@vu.nl)
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K. F. Boersma corresponding
Royal Netherlands Meteorological Institute · Wageningen University & Research
Affiliation as printed
Royal Netherlands Meteorological Institute, R&D Satellite Observations, De Bilt, the Netherlands
Wageningen University, Meteorology and Air Quality Section, Wageningen, the Netherlands
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Space Research Organisation Netherlands · Vrije Universiteit Amsterdam
Affiliation as printed
SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
Vrije Universiteit, Department of Physics and Astronomy, Amsterdam, the Netherlands
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Hugo Denier van der Gon corresponding
Netherlands Organisation for Applied Scientific Research
Affiliation as printed
TNO, Department of Climate, Air and Sustainability, Utrecht, the Netherlands
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Utrecht University · Wageningen University & Research
Affiliation as printed
Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands
Wageningen University, Meteorology and Air Quality Section, Wageningen, the Netherlands
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Albertus Johannes Dolman corresponding
Affiliation as printed
Vrije University of Amsterdan , Earth Science, Netherlands (s.lama@vu.nl)
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
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Space Research Organisation Netherlands
Affiliation as printed
SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
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