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| Titel |
Vital improvements to the retrieval of tropospheric NO2 columns from the Ozone Monitoring Instrument |
| VerfasserIn |
Joannes D. Maasakkers, K. Folkert Boersma, Jason E. Williams, Jos van Geffen, Geert C. M. Vinken, Maarten Sneep, Francois Hendrick, Michel Van Roozendael, J. Pepijn Veefkind |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072275
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| Zusammenfassung |
| Nitrogen oxides (NOx = NO + NO2) play an important role in tropospheric chemistry, they
catalyze the production of ozone (O3) and contribute to aerosol formation. NOx is linked to
the oxidizing efficiency of the atmosphere since O3 plays an important role in the formation
of OH. Satellite observations of NO2 are important for monitoring and studying
concentrations of nitrogen oxides, but considerable uncertainties on the accuracy and
robustness of the retrievals, and their fitness for model evaluation still persist. These
uncertainties pertain to all aspects of the retrieval: (1) spectral fitting, (2) stratospheric
background correction, and (3) air mass factor calculation.
Here we present a number of relevant improvements to the tropospheric nitrogen dioxide
column retrieval algorithm from OMI (DOMINO v3). We revisit the 405-465 nm spectral
fitting window for the OMI NO2 slant column retrievals, and suggest adaptations to this
window to improve agreement with (stratospheric) columns obtained from SCIAMACHY
and GOME-2, as validated with independent FTIR NO2 columns observed from the ground
at Jungfraujoch. Furthermore, stronger nudging of the stratospheric O3:HNO3 ratios in the
TM5 chemistry transport model (used to estimate the stratospheric background NO2) with
those observed by the ODIN instrument, enables us to improve stratospheric NO2 simulations
with substantial benefits for the assimilation and stratospheric NO2 corrections
in the retrieval. A third important innovation is the coupling of the Dutch OMI
NO2 retrieval to the TM5 model with a global resolution of 1°Ã1°. As suggested
previously by Boersma et al. [2007] and demonstrated by Heckel et al. [2011],
the better resolved a priori profile shapes lead to a much better understanding of
pollution gradients observed from space. In addition to the increased resolution,
updated chemistry and emissions (improved soil and ship NOx emissions) in TM5
make the OMI retrieved tropospheric NO2 columns significantly more realistic.
Tropospheric columns over western Europe decrease, while the wildfire related
increased concentrations are better captured. The improvements discussed here
are applicable to current OMI retrievals, but are also highly relevant in view of
algorithm needs for the future TROPOMI (8Ã8 km2) and GMES Sentinel-4 sensors. |
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