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| Titel |
Modeling ozone plumes observed downwind of New York City over the North Atlantic Ocean during the ICARTT field campaign |
| VerfasserIn |
S.-H. Lee, S.-W. Kim, M. Trainer, G. J. Frost, S. A. McKeen, O. R. Cooper, F. Flocke, J. S. Holloway, J. A. Neuman, T. Ryerson, C. J. Senff, A. L. Swanson, A. M. Thompson |
| 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 ; 11, no. 14 ; Nr. 11, no. 14 (2011-07-26), S.7375-7397 |
| Datensatznummer |
250009952
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| Publikation (Nr.) |
 copernicus.org/acp-11-7375-2011.pdf |
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| Zusammenfassung |
| Transport and chemical transformation of well-defined New York City (NYC)
urban plumes over the North Atlantic Ocean were studied using aircraft
measurements collected on 20–21 July 2004 during the ICARTT (International
Consortium for Atmospheric Research on Transport and Transformation) field
campaign and WRF-Chem (Weather Research and Forecasting-Chemistry) model
simulations. The strong NYC urban plumes were characterized by carbon
monoxide (CO) mixing ratios of 350–400 parts per billion by volume (ppbv)
and ozone (O3) levels of about 100 ppbv near New York City on 20 July
in the WP-3D in-situ and DC-3 lidar aircraft measurements. On 21 July, the
two aircraft captured strong urban plumes with about 350 ppbv CO and over
150 ppbv O3 (~160 ppbv maximum) about 600 km downwind of NYC over
the North Atlantic Ocean. The measured urban plumes extended vertically up
to about 2 km near New York City, but shrank to 1–1.5 km over the stable
marine boundary layer (MBL) over the North Atlantic Ocean. The WRF-Chem
model reproduced ozone formation processes, chemical characteristics, and
meteorology of the measured urban plumes near New York City (20 July) and in
the far downwind region over the North Atlantic Ocean (21 July). The
quasi-Lagrangian analysis of transport and chemical transformation of the
simulated NYC urban plumes using WRF-Chem results showed that the pollutants
can be efficiently transported in (isentropic) layers in the lower
atmosphere (<2–3 km) over the North Atlantic Ocean while maintaining a
dynamic vertical decoupling by cessation of turbulence in the stable MBL.
The O3 mixing ratio in the NYC urban plumes remained at 80–90 ppbv
during nocturnal transport over the stable MBL, then grew to over 100 ppbv
by daytime oxidation of nitrogen oxides (NOx = NO + NO2) with
mixing ratios on the order of 1 ppbv. Efficient transport of reactive
nitrogen species (NOy), specifically nitric acid (HNO3), was
confirmed through the comparison of the CO/NOy ratio in photochemically
fresh and aged NYC plumes, implying the possibility of long-range transport
of O3 over the stable MBL over the North Atlantic Ocean in association
with NOx regeneration mechanism. The impact of chemical initial and
boundary conditions (IC/BCs) on modelled O3 urban plumes was
investigated in terms of the background O3 level and the vertical
structure of the urban plumes. Simulations with dynamic ("time-variant")
chemical IC/BCs enhanced the O3 level by 2–12 ppbv on average in the
atmospheric layer below 3 km, showing better agreement with the observed NYC
plumes and biomass-burning plumes than the simulation with prescribed static
IC/BCs. The simulation including MOZART-4 chemical IC/BCs and
Alaskan/Canadian wildfire emissions compared better to the observed O3
profiles in the upper atmospheric layer (>~3 km) than models that
only accounted for North American anthropogenic/biogenic and wildfire
contributions to background ozone. The comparison between models and
observations show that chemical IC/BCs must be properly specified to achieve
accurate model results. |
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