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| Titel |
Characterization of OMI tropospheric NO2 over the Baltic Sea region |
| VerfasserIn |
I. Ialongo, J. Hakkarainen, N. Hyttinen, J.-P. Jalkanen, L. Johansson, K. F. Boersma, N. Krotkov, J. Tamminen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 15 ; Nr. 14, no. 15 (2014-08-05), S.7795-7805 |
| Datensatznummer |
250118923
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| Publikation (Nr.) |
 copernicus.org/acp-14-7795-2014.pdf |
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| Zusammenfassung |
Satellite-based data are very important for air-quality applications in the
Baltic Sea region, because they provide information on air pollution over the
sea and where ground-based and aircraft measurements are not available. Both
the emissions from urban sites over land and ships over sea, contribute to
tropospheric NO2 levels. Tropospheric NO2 monitoring at high
latitudes using satellite data is challenging because of the reduced light
hours in winter and the weak signal due to the low Sun, which make the
retrieval complex.
This work presents a characterization of tropospheric NO2 columns based
on case-study analysis in the Baltic Sea region, using the Ozone Monitoring
Instrument (OMI) tropospheric NO2 standard product. Previous works have
focused on larger seas and lower latitudes. The results of this paper showed
that, despite the regional area of interest, it is possible to distinguish
the signal from the main coastal cities and from the ships by averaging the
data over a~seasonal time range. The summertime NO2 emission and
lifetime values (E' = (1.5 ± 0.6) mol s−1 and
τ = (3 ± 1) h, respectively) in Helsinki were estimated from
the decay of the signal with distance from the city center. These results
agree within the uncertainties with the emissions from the existing database. For
comparison, the results for the cities of Saint Petersburg and Stockholm are
also shown. The method developed for megacities was successfully applied to
smaller-scale sources, in both size and intensity, which are located at high
latitudes (~60° N). The same methodology could be applied to
similar-scale cities elsewhere, as long as they are relatively isolated from
other sources.
Transport by the wind plays an important role in the Baltic Sea region. The
NO2 spatial distribution is mainly determined by the contribution of
westerly winds, which dominate the wind patterns during summer. The
comparison between the ship emissions from model calculations and OMI
NO2 tropospheric columns supports the applicability of satellite data
for ship emission monitoring. In particular, both the ship emission data and
the OMI observations showed similar year-to-year variability, with a drop in
the year 2009, corresponding to the effect of the financial crisis. |
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