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| Titel |
Effects of dust aerosols on tropospheric chemistry during a typical pre-monsoon season dust storm in northern India |
| VerfasserIn |
R. Kumar, M. C. Barth, S. Madronich, M. Naja, G. R. Carmichael, G. G. Pfister, C. Knote, G. P. Brasseur, N. Ojha, T. Sarangi |
| 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. 13 ; Nr. 14, no. 13 (2014-07-04), S.6813-6834 |
| Datensatznummer |
250118865
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| Publikation (Nr.) |
 copernicus.org/acp-14-6813-2014.pdf |
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| Zusammenfassung |
| This study examines the effect of a typical pre-monsoon season dust storm on
tropospheric chemistry through a case study in northern India. Dust can
alter photolysis rates by scattering and absorbing solar radiation and
provide surface area for heterogeneous reactions. We use the Weather
Research and Forecasting model coupled with Chemistry (WRF-Chem) to simulate
the dust storm that occurred during 17–22 April 2010 and investigate the
contribution of different processes on mixing ratios of several key trace
gases including ozone, nitrogen oxides, hydrogen oxides, methanol, acetic
acid and formaldehyde. We revised the Fast Troposphere Ultraviolet Visible
(F-TUV) photolysis scheme to include effects of dust aerosols on photolysis
rates in a manner consistent with the calculations of aerosol optical
properties for feedback to the meteorology radiation schemes. In addition,
we added 12 heterogeneous reactions on the dust surface, for which 6
reactions have relative-humidity-dependent reactive uptake coefficients
(γ). The inclusion of these processes in WRF-Chem is found to reduce
the difference between observed and modeled O3 from 16 ± 9 to
2 ± 8 ppbv and that in NOy from 2129 ± 1425 to
372 ± 1225 pptv compared to measurements at the high-altitude site
Nainital in the central Himalayas, and reduce biases by up to 30% in
tropospheric column NO2 compared to OMI retrievals. The simulated dust
storm acted as a sink for all the trace gases examined here and
significantly perturbed their spatial and vertical distributions. The
reductions in these gases are estimated as 5–100%, and more than 80% of
this reduction was due to heterogeneous chemistry. The RH dependence of
γ is also found to have substantial impact on the distribution of
trace gases, with changes of up to 20–25% in O3 and HO2, 50%
in H2O2 and 100% in HNO3. A set of sensitivity analyses
revealed that dust aging could change H2O2 and CH3COOH levels
by up to 50% but has a relatively small impact on other gases. |
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