A013-06
Quantifying burning efficiency in Megacities using the NO2/CO ratio from the Tropospheric Monitoring Instrument (TROPOMI)

Monday, 7 December 2020: 06:02
Virtual
Srijana Lama1, Sander Houweling2,3, Folkert Boersma4,5, Henk Eskes6, Ilse Aben3,7, Hugo Denier Van Der Gon8, Maarten C Krol9,10, A Johannes Dolman11, Tobias Borsdorff3 and Alba Lorente3, (1)Vrije Universiteit Amsterdam, Amsterdam, Netherlands, (2)VU University Amsterdam, Faculty of Science, Amsterdam, Netherlands, (3)SRON Netherlands Institute for Space Research, Utrecht, Netherlands, (4)Royal Netherlands Meteorological Institute, De Bilt, Netherlands, (5)Wageningen University, Meteorology and Air Quality, Wageningen, Netherlands, (6)Royal Netherlands Meteorological Institute, De Bilt, 3730, Netherlands, (7)Vrije Universiteit Amsterdam, Department of Physics and Astronomy, Amsterdam, Netherlands, (8)TNO, Utrecht, Netherlands, (9)Utrecht University, Utrecht, Netherlands, (10)Wageningen University and Research, Wageningen, Netherlands, (11)Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands
Recorded Presentation
Abstract:
The increase in fuel consumption with the economic growth and urbanization of megacities has degraded the urban air quality. Burning efficiency is an important parameter determining the impact of fuel burning on the environment. The burning efficiency changes with environmental conditions and affects the ratio by which pollutants are emitted, as expressed by emission factors. The use of emission factors, which are generally measured under controlled laboratory conditions, is a major source of uncertainty in global emission inventories.

In this study, co-located TROPOMI CO and NO2 retrievals are used over six megacities (Tehran, Cairo, Riyadh, Lahore, Mexico City and Los Angeles) to investigate their potential use for independent evaluation of emission factors. On 13th of October, 2017, TROPOMI was successfully launched onboard of the European Space Agency's (ESA) Sentinel‐5P satellite. It measures atmospheric trace gases with daily coverage and a spatial resolution of 7x5.5 km2. At this resolution, TROPOMI is able to detect the hot spots of CO and NO2 in a single overpass. TROPOMI inferred column enhancement ratios (∆NO2/∆CO) from Upwind Background and Plume Rotation method are compared with Emission Database for Global Atmospheric Research (EDGAR v4.3.2) and Monitoring Atmospheric Chemistry and Climate and CityZen (MACCity) 2018 emission inventories. TROPOMI shows a strong correlation (r = 0.85 and 0.7) with EDGAR and MACCity, showing highest ratio for Riyadh and lowest for Lahore. However, inventory derived emission ratios are larger by 60 to 85 % than TROPOMI derived NO2/CO ratios. This difference is mostly explained by the short lifetime of NO2 and the different vertical sensitivities of TROPOMI NO2 and CO retrievals. We present a method for transforming TROPOMI derived column enhancement ratios into corresponding emission ratios, considering these effects. TROPOMI derived emission ratios are close to the MACCity emission ratio (10 to 25 %), but a discrepancy remains up to 65% with EDGAR. For Los Angeles, EDGAR and MACCity the ratio is overestimated by 50% and 70%, respectively, compared to TROPOMI. Validation results using the air quality network in Los Angeles are consistent with TROPOMI inferred emission ratio confirming our TROPOMI-inferred estimates, and the promising potential of this approach.

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