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| Titel |
Influences of Meteorological Anomalies on An Extreme Winter Haze Event in Beijing - A Numerical Study Using WRF-Chem |
| VerfasserIn |
Li Zhang, Tao Wang, Qiaozhi Zha, Menyao Lv, Qiang Zhang |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089107
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| Publikation (Nr.) |
 EGU/EGU2014-3298.pdf |
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| Zusammenfassung |
| Beijing has made great efforts to reduce anthropogenic emissions for the last decade and its
air quality, consequently, does show a slight improvement since 2007 as reflected by the
decreasing Air Pollution Index (API) trend. However, during the January 2013,
this megacity was frequently shrouded by heavy haze and the PM2.5 observed in
an urban site was higher than 75 μg m-3for two thirds of that month. On 12th
January, an unprecedented haze event assaulted Beijing with the daily PM2.5 soared
to 568.5 μg m-3 and API hit the upper limit. Through the analysis of historical
meteorological data, we found that Beijing experienced the lowest average wind
speed and the highest relative humidity (RH) in this January since 2000 and the
frequency of prevailing northerly winter winds was abnormally low. We suggested that
the high PM2.5 levels during this month including the extreme haze were mainly
attributed to the climate anomalies in wind and RH. A series of simulations using a
coupled meteorology-chemistry model (WRF-Chem) was used to study the role of
the unique climate anomalies played in the episode as a case. The unusual week
winds at surface and strong southerly winds at the 300-900 m layer created a strong
temperature inversion and thus humidity and pollutants were trapped within the
shallow boundary layer beneath the inversion, which was the main reason for the
episode. Sensitivity simulations suggested that the local emission was the major
contributor at the surface (40 m) whereas the regional contribution dominated at
the upper layer (40-1500 m). Emergency and more stringent long-term emission
controls should be applied in Beijing and surrounding provinces to prevent severe
pollutions in case similar anomalous meteorological conditions occur again. During the
episode, both surface weather pattern and transport pathway showed unique behaviors
under the climate anomalies. The transport pathway even extended from the East
China Plain, indicating that emission reductions over a wider area are also needed. |
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