What caused the extreme CO concentrations during the 2017 high pollution episode in India?

Iris Dekker, S. Houweling, S. Pandey, M.C. Krol, T. Roeckmann, Tobias Borsdorff, Jochen Landgraf, I. Aben

Research output: Contribution to journalArticleAcademic

Abstract

The TROPOspheric Monitoring Instrument (TROPOMI), launched 13 October 2017, measures carbon monoxide (CO) concentrations in the Earth's atmosphere since early November 2017. In the first measurements, TROPOMI was able to measure CO concentrations of the high pollution event in India of November 2017. In this paper we studied the extent of the pollution in India, comparing the TROPOMI CO with modelled data from the Weather Research and Forecast model (WRF) to identify the most important sources contributing to the high pollution, both at ground-level and in the total column. We investigated the period between 11 and 19 November 2017. We found that residential and commercial combustion was a much more important source of CO pollution than the post-monsoon crop burning during this period, which is in contrast to what media suggested and some studies on aerosol emissions found. Also, the high pollution was not limited to Delhi and its direct neighbourhood but the accumulation of pollution extended over the whole Indo-Gangetic Plain (IGP) due to the unfavourable weather conditions in combination with extensive emissions. From the TROPOMI data and WRF simulations, we observed a build-up of CO during 11–14 November and a decline in CO after the 15th of November. The meteorological situation, characterized by low wind speeds and shallow atmospheric boundary layers, was most likely the primary explanation for the temporal accumulation and subsequent dispersion of regionally emitted CO in the atmosphere, emphasizing the important role of atmospheric dynamics. Due to its rapidly growing population and economy, India is expected to encounter similar pollution events more often in future post-monsoon and winter seasons unless significant policy measures are taken to reduce residential and commercial emissions.
Original languageEnglish
JournalAtmospheric Chemistry and Physics Discussions
DOIs
Publication statusPublished - 13 Nov 2018

Keywords

  • Air Quality
  • Carbon monoxide
  • India
  • pollution
  • post-monsoon
  • fire
  • TROPOMI

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