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Direct observations of megacity emissions and lifetimes of nitrogen oxides using OMI

  • Emission inventories in megacities are uncertain, particularly in developing countries.
  • Can we use OMI to better quantify these emissions without a model?
  • By analyzing the downwind patterns of NO2 for different wind conditions, we simultaneously determine megacity NOx emissions and lifetimes from OMI.
  • Estimated daytime lifetimes are ~4 hours at low and mid-latitudes, but ~8 hours in wintertime for Moscow.
  • Derived NOx emissions are is reasonable agreement with global emission inventories, but are higher by a factor of 3 for the Saudi-Arabian capital Riyadh.

The wind dependency of NO2 column densities around Riyadh.
   NO2 tropospheric columns in the Middle East

Above Left: Mean NO2 tropospheric columns in the Middle East from OMI measurements during 2005-2009 for calm (w<2 m/s) conditions with <30% cloud cover. The grey box indicates Riyadh and the surrounding area. Above Right: Mean NO2 column densities around Riyadh (white cross) for different wind conditions, i.e. calm (center panel) and 8 main wind direction sectors (surrounding panels; arrows indicate the mean of the respective ECMWF winds).
Left: The resulting NOx emissions and lifetimes. Scatterplot of the resulting NOx emissions for the considered megacities and power plants versus the respective EDGAR emissions (V4.1, integrated over 250_250 km2). Resulting NOx lifetimes are color coded.

Feature Released 11.04.2011

Credit : Beirle et al. (2011) Science, courtesy F. Boersma (KNMI)