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| Titel |
First estimates of global free-tropospheric NO2 abundances derived using a cloud-slicing technique applied to satellite observations from the Aura Ozone Monitoring Instrument (OMI) |
| VerfasserIn |
S. Choi, J. Joiner, Y. Choi, B. N. Duncan, A. Vasilkov, N. Krotkov, E. Bucsela |
| 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. 19 ; Nr. 14, no. 19 (2014-10-09), S.10565-10588 |
| Datensatznummer |
250119084
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| Publikation (Nr.) |
 copernicus.org/acp-14-10565-2014.pdf |
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| Zusammenfassung |
| We derive free-tropospheric NO2 volume mixing ratios (VMRs)
by applying a cloud-slicing technique to data from the Ozone Monitoring Instrument (OMI)
on the Aura satellite. In the cloud-slicing approach, the slope of
the above-cloud NO2 column versus the cloud scene pressure is
proportional to the NO2 VMR. In this work, we use a sample
of nearby OMI pixel data from a single orbit for the linear fit. The
OMI data include cloud scene pressures from the rotational-Raman
algorithm and above-cloud NO2 vertical column density (VCD)
(defined as the NO2 column from the cloud scene pressure to
the top of the atmosphere) from a differential optical absorption
spectroscopy (DOAS) algorithm.
We compare OMI-derived NO2 VMRs with in situ
aircraft profiles measured during the NASA Intercontinental Chemical
Transport Experiment Phase B (INTEX-B) campaign in 2006. The
agreement is generally within the estimated uncertainties when
appropriate data screening is applied. We then derive a global
seasonal climatology of free-tropospheric NO2 VMR in cloudy
conditions. Enhanced NO2 in the free troposphere commonly
appears near polluted urban locations where NO2 produced in
the boundary layer may be transported vertically out of the boundary
layer and then horizontally away from the source. Signatures of
lightning NO2 are also shown throughout low and middle
latitude regions in summer months. A profile analysis of our cloud-slicing data indicates signatures of
lightning-generated NO2 in the upper troposphere.
Comparison of the climatology with simulations from the global
modeling initiative (GMI) for cloudy conditions (cloud optical
depth > 10) shows similarities in the spatial patterns of
continental pollution outflow. However, there are also some
differences in the seasonal variation of free-tropospheric
NO2 VMRs near highly populated regions and in areas affected
by lightning-generated NOx. |
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