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| Titel |
The impact of circulation patterns on regional transport pathways and air quality over Beijing and its surroundings |
| VerfasserIn |
J. P. Zhang, T. Zhu, Q. H. Zhang, C. C. Li, H. L. Shu, Y. Ying, Z. P. Dai, X. Wang, X. Y. Liu, A. M. Liang, H. X. Shen, B. Q. Yi |
| 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 ; 12, no. 11 ; Nr. 12, no. 11 (2012-06-07), S.5031-5053 |
| Datensatznummer |
250011227
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| Publikation (Nr.) |
 copernicus.org/acp-12-5031-2012.pdf |
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| Zusammenfassung |
This study investigated the air pollution characteristics of synoptic-scale
circulation in the Beijing megacity, and provided quantitative evaluation of
the impacts of circulation patterns on air quality during the 2008 Beijing
Summer Olympics. Nine weather circulation types (CTs) were objectively
identified over the North China region during 2000–2009, using obliquely
rotated T-mode principal component analysis (PCA). The resulting CTs were
examined in relation to the local meteorology, regional transport pathways,
and air quality parameters, respectively. The FLEXPART-WRF model was used to
calculate 48-h backward plume trajectories for each CT. Each CT was
characterized with distinct local meteorology and air mass origin. CT 1
(high pressure to the west with a strong pressure gradient) was
characterized by a northwestern air mass origin, with the smallest local and
southeasterly air mass sources, and CT 6 (high pressure to the northwest)
had air mass sources mostly from the north and east. On the contrary, CTs 5,
8, and 9 (weak pressure field, high pressure to the east, and low pressure
to the northwest, respectively) were characterized by southern and
southeastern trajectories, which indicated a greater influence of high
pollutant emission sources. In turn, poor air quality in Beijing (high
loadings of PM10, BC, SO2, NO2, NOx, O3, AOD, and
low visibility) was associated with these CTs. Good air quality in Beijing
was associated with CTs 1 and 6. The average visibilities (with ±1σ)
in Beijing for CTs 1 and 6 during 2000–2009 were 18.5 ± 8.3 km and 14.3 ± 8.5 km, respectively. In contrast, low visibility
values of 6.0 ± 3.5 km, 6.6 ± 3.7 km, and 6.7 ± 3.6 km were
found in CTs 5, 8, and 9, respectively. The mean concentrations of PM10
for CTs 1, 6, 5, 8, and 9 during 2005–2009 were 90.3 ± 76.3 μg m−3,
111.7 ± 89.6 μg m−3, 173.4 ± 105.8 μg m−3,
158.4 ± 90.0 μg m−3, and 151.2 ± 93.1 μg m−3,
respectively.
Analysis of the relationship between circulation pattern and air quality
during the emission control period suggests that CTs are the primary drivers
of day-to-day variations in pollutant concentrations over Beijing and its
vicinity. During the Olympics period, the frequency of CT 6 was twice that
of the mean in August from 2000 to 2009. This CT had northerly transport
pathways and favorable meteorological conditions (e.g. frequent
precipitation) for clean air during the Olympics. Assuming that
relationships between CTs and air quality parameters in the same season are
fixed in different years, the relative contributions of synoptic circulation
to decreases in PM10, BC, SO2, NO2, NOx, CO, and
horizontal light extinction during the Olympics were estimated as
19 ± 14%, 18 ± 13%, 41 ± 36%, 12 ± 7%,
10 ± 5%, 19 ± 11%, and 54 ± 25%, respectively. |
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