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| Titel |
On the improvement of NO2 satellite retrievals – aerosol impact on the airmass factors |
| VerfasserIn |
J. Leitão, A. Richter, M. Vrekoussis, A. Kokhanovsky, Q. J. Zhang, M. Beekmann, J. P. Burrows |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 3, no. 2 ; Nr. 3, no. 2 (2010-04-16), S.475-493 |
| Datensatznummer |
250000977
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| Publikation (Nr.) |
 copernicus.org/amt-3-475-2010.pdf |
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| Zusammenfassung |
| The accurate determination of nitrogen dioxide (NO2) tropospheric
vertical columns from satellite measurements depends strongly on the airmass
factor (AMF) used. A sensitivity study was performed with the radiative
transfer model SCIATRAN to better understand the impact of aerosols on the
calculation of NO2 AMFs. This influence was studied by varying the
NO2 and aerosol vertical distributions, as well as physical and optical
properties of the particles. In terms of aerosol definitions, the key
factors for these calculations were identified as the relation between trace
gas and aerosol vertical profiles, the optical depth of the aerosol layer,
and single scattering albedo. In addition, surface albedo also has a large
impact on the calculations. Overall it was found that particles mixed with
the trace gas increases the measurements' sensitivity, but only when the
aerosol is not very absorbing. The largest change, a factor of ~2
relative to the situation without aerosols, was found when a low layer of
aerosol (600 m) was combined with a homogenous NO2 layer of 1.0 km. A
layer of aerosol above the NO2 usually reduces the sensitivity of the
satellite measurement. This situation is found mostly for runs with discrete
elevated aerosol layers (representative for long-range transport) that can
generate a decrease of the AMF values of up to 70%. The use of measured
aerosol profiles and modelled NO2 resulted, generally, in much smaller
changes of AMF relative to the pure Rayleigh case. Exceptions are some
events of elevated layers with high aerosol optical depth that lead to a
strong decrease of the AMF values. These results highlight the importance of
aerosols in the retrieval of tropospheric NO2 columns from space and
indicate the need for detailed information on aerosol properties and
vertical distribution. |
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