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| Titel |
Nitrogen oxides in the global upper troposphere interpreted with cloud-sliced NO2 from the Ozone Monitoring Instrument |
| VerfasserIn |
Eloise A. Marais, Daniel J. Jacob, Sungyeon Choi, Joanna Joiner, Maria Belmonte-Rivas, Ronald C Cohen, Thomas B. Ryerson, Andrew J. Weinheimer, Andreas Volz-Thomas |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250147936
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| Publikation (Nr.) |
 EGU/EGU2017-12156.pdf |
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| Zusammenfassung |
| Nitrogen oxides (NOx ≡ NO + NO2) are long lived in the upper troposphere (UT), and so
have a large impact on ozone formation where ozone is a powerful greenhouse gas.
Measurements of UT NOx are limited to summertime aircraft campaigns predominantly in
North America. There are year-round NOx measurements from instruments onboard
commercial aircraft, but NO2 measurements are susceptible to large interferences. Satellites
provide global coverage, but traditional space-based NO2 observations only provide one
piece of vertical information in the troposphere. New cloud-sliced satellite NO2 products
offer additional vertical information by retrieving partial NO2 columns above clouds and
further exploit differences in cloud heights to calculate UT NO2 mixing ratios. Two new
cloud-sliced NO2 products from the Ozone Monitoring Instrument (OMI; 2004 launch)
provide seasonal UT NO2 data centered at 350 hPa for 2005-2007 (NASA product) and 380
hPa for 2006 only (KNMI). Differences between the products include spectral fitting to
obtain NO2 along the viewing path (slant column), the air mass factor calculation to
convert slant columns to true vertical columns, treatment of the stratospheric NO2
component, and the choice of cloud products. The resultant NASA NO2 mixing
ratios are 30% higher than KNMI NO2 and are consistent with summertime aircraft
NO2 observations over North America. Comparison between NASA NO2 and the
GEOS-Chem chemical transport model exposes glaring inadequacies in the model. In
summer in the eastern US lightning NOx emissions are overestimated by at least a
factor of 2, corroborated by comparison of GEOS-Chem and MOZAIC aircraft
observations of reactive nitrogen (NOy). Too fast heterogeneous hydrolysis of dinitrogen
pentoxide (N2O5) leads to an underestimate in UT NO2 in winter across the northern
hemisphere. Absence of interannual variability in lightning flashes in the lightning NOx
parameterization induces biases in UT NO2 in the tropics due to anomalous lightning activity
linked to the El Niño Southern Oscillation. Ongoing work is to use GEOS-Chem
to investigate the implications of updated representation of UT NOx on ozone. |
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