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| Titel |
Megacity NOx emissions and lifetimes probed from space |
| VerfasserIn |
S. Beirle, K. F. Boersma, U. Platt, M. Lawrence, T. Wagner |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250067937
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| Zusammenfassung |
| Megacity emission inventories, based on bottom-up estimates, are still highly uncertain, in particular in developing countries. Satellite observations have been demonstrated to allow regional and global top-down emission estimates of nitrogen oxides (NOx=NO+NO2), but require poorly quantified a-priori information on the lifetime of NOx.
Here we present a new method for the determination of megacity NOx emissions and lifetimes from satellite measurements. Mean patterns of NO2 tropospheric columns are analyzed separately for a set of different wind direction sectors. From the combined use of the observed total burden and the downwind evolution of NO2, mean NOx photochemical lifetimes and total emissions are derived simultaneously.
Typical daytime lifetimes of about 4 hours are found for several megacities at low and mid- latitudes, corresponding to mean OH concentrations of ~6e6 molec/cm3 around noon. The derived emissions are generally in good agreement with bottom-up inventories, but are significantly higher in e.g. the case of Riyadh (Saudi Arabia).
The presented method works best for isolated "hot spots" of NOx emissions. For megacities in the vicinity (in terms of some hundred km) of other strong sources, like e.g. Paris, modified approaches are necessary. We will present different approaches, and the estimated emissions+uncertainties will be discussed in perspective of existing, bottom-up emission inventories. |
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