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| Titel |
Investigation of NO2 vertical distribution from satellite data by using two NO2 DOAS retrievals |
| VerfasserIn |
Lisa K. Behrens, Andreas Hilboll, Andreas Richter, Enno Peters, John P. Burrows |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131617
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| Publikation (Nr.) |
 EGU/EGU2016-12045.pdf |
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| Zusammenfassung |
| NO2 is an important indicator for air pollution from anthropogenic as well as natural
sources. NOx emission sources and their horizontal distribution are well known from
satellite measurements. In contrast, knowledge of the vertical NO2 distribution is only
limited. To address this issue we developed a new NO2 differential optical absorption
spectroscopy (DOAS) retrieval in the UV spectral range for satellite observations from
the GOME-2 instrument on board EUMETSAT’s MetOp-A satellite. This new
UV NO2 retrieval is compared to a common NO2 retrieval in the visible spectral
range.
Here we show that by using retrievals in the UV and visible, sensitivity to the vertical
distribution of NO2 can be achieved in satellite measurements. Box air mass factor
calculations show that sensitivity below 9km is clearly higher in the visible spectral range
whereas above 9km, the sensitivity is somewhat higher in the UV range. Due to the higher
sensitivity of the visible spectral range closer to the ground, the NO2 slant columns derived
from the visible spectral range are mostly higher than in the UV spectral range. Nevertheless,
our new NO2 retrieval and the common NO2 retrieval from the visible spectral range
show a similar horizontal distribution. In both spectral ranges, well known NO2
signals over highly polluted areas, e.g., China or biomass burning areas like Africa
south of the equator can be observed. However in some areas, NO2 signals clearly
visible in the visible spectral range cannot be detected in the UV spectral range,
such as in Africa north of the equator over the biomass burning regions. From the
differences in NO2 slant columns, we can gain insight into the vertical distribution of
NO2.
By using air mass factors, slant columns can be converted into vertical columns. For air
mass factor calculations, an a priori NO2 profile is needed from model simulations, here the
MACC2 interim reanalysis fields. If the model simulates the NO2 profile with correct height
dependency, there should be no differences in NO2 vertical columns for the two wavelength
ranges. Therefore, we can gain additional information about the NO2 height dependency
from a comparison of vertical columns. In some regions the vertical columns agree well.
However, there are also regions with large differences in NO2 vertical columns, especially in
winter season. |
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