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| Titel |
Space-based retrieval of NO2 over biomass burning regions: quantifying and reducing uncertainties |
| VerfasserIn |
N. Bousserez |
| 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 ; 7, no. 10 ; Nr. 7, no. 10 (2014-10-08), S.3431-3444 |
| Datensatznummer |
250115928
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| Publikation (Nr.) |
 copernicus.org/amt-7-3431-2014.pdf |
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| Zusammenfassung |
| The accuracy of space-based nitrogen dioxide (NO2) retrievals from solar
backscatter radiances critically depends on a priori knowledge of the
vertical profiles of NO2 and aerosol optical properties. This
information is used to calculate an air mass factor (AMF), which accounts for
atmospheric scattering and is used to convert the measured line-of-sight
"slant" columns into vertical columns. In this study we investigate the
impact of biomass burning emissions on the AMF in order to quantify NO2
retrieval errors in the Ozone Monitoring Instrument (OMI) products over these
sources. Sensitivity analyses are conducted using the Linearized Discrete
Ordinate Radiative Transfer (LIDORT) model. The NO2 and aerosol profiles
are obtained from a 3-D chemistry-transport model (GEOS-Chem), which uses the
Fire Locating and Monitoring of Burning Emissions (FLAMBE) daily biomass
burning emission inventory. Aircraft in situ data collected during two field
campaigns, the Arctic Research of the Composition of the Troposphere from
Aircraft and Satellites (ARCTAS) and the Dust and Biomass-burning Experiment
(DABEX), are used to evaluate the modeled aerosol optical properties and
NO2 profiles over Canadian boreal fires and West African savanna fires,
respectively. Over both domains, the effect of biomass burning emissions on
the AMF through the modified NO2 shape factor can be as high as −60%.
A sensitivity analysis also revealed that the effect of aerosol and shape
factor perturbations on the AMF is very sensitive to surface reflectance and
clouds. As an illustration, the aerosol correction can range from −20 to
+100% for different surface reflectances, while the shape factor
correction varies from −70 to −20%. Although previous studies have
shown that in clear-sky conditions the effect of aerosols on the AMF was in
part implicitly accounted for by the modified cloud parameters, here it is
suggested that when clouds are present above a surface layer of scattering
aerosols, an explicit aerosol correction would be beneficial to the NO2
retrieval. Finally, a new method that uses slant column information to
correct for shape-factor-related AMF error over NOx emission
sources is proposed, with possible application to near-real-time OMI
retrievals. |
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