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| Titel |
Modeling natural emissions in the Community Multiscale Air Quality (CMAQ) model – Part 2: Modifications for simulating natural emissions |
| VerfasserIn |
S. F. Mueller, Q. Mao, J. W. Mallard |
| 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. 1 ; Nr. 11, no. 1 (2011-01-14), S.293-320 |
| Datensatznummer |
250009072
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| Publikation (Nr.) |
 copernicus.org/acp-11-293-2011.pdf |
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| Zusammenfassung |
| The Community Multiscale Air Quality (CMAQ) model version 4.6 has been
revised with regard to the representation of chlorine (HCl, ClNO2) and
sulfur (dimethylsulfide, or DMS, and H2S), and evaluated against
observations and earlier published models. Chemistry parameterizations were
based on published reaction kinetic data and a recently developed cloud
chemistry model that includes heterogeneous reactions of organic sulfur
compounds. Evaluation of the revised model was conducted using a recently
enhanced data base of natural emissions that includes ocean and continental
sources of DMS, H2S, chlorinated gases and lightning NOx for the
continental United States and surrounding regions. Results using 2002
meteorology and emissions indicated that most simulated "natural" (plus background) chemical and aerosol
species exhibit the expected seasonal variations at the surface. Ozone
exhibits a winter and early spring maximum consistent with ozone data and
an earlier published model. Ozone distributions reflect the influences of
atmospheric dynamics and pollutant background levels imposed on the CMAQ
simulation by boundary conditions derived from a global model. A series of
model experiments reveals that the consideration of gas-phase organic sulfur
chemistry leads to sulfate aerosol increases over most of the continental
United States. Cloud chemistry parameterization changes result in widespread
decreases in SO2 across the modeling domain and both increases and
decreases in sulfate. Most cloud-mediated sulfate increases occurred mainly
over the Pacific Ocean (up to about 0.1 μg m−3) but also over and
downwind from the Gulf of Mexico (including parts of the eastern US).
Geographic variations in simulated SO2 and sulfate are due to the link
between DMS/H2S and their byproduct SO2, the heterogeneity of
cloud cover and precipitation (precipitating clouds act as net sinks for
SO2 and sulfate), and the persistence of cloud cover (the largest
relative sulfate increases occurred over the persistently cloudy Gulf of
Mexico and western Atlantic Ocean). Overall, the addition of organic sulfur
chemistry increased hourly surface sulfate levels by up to 1–2 μg m−3 but reduced sulfate levels in the vicinity of high SO2
emissions (e.g., wildfires). Simulated surface levels of DMS compare
reasonably well with observations in the marine boundary layer where DMS
oxidation product levels are lower than observed. This implies either a low
bias in model oxidation rates of organic sulfur species or a low bias in the
boundary conditions for DMS oxidation products. This revised version of CMAQ
provides a tool for realistically simulating the influence of natural
emissions on air quality. |
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