Analysis of the causes of heavy aerosol pollution in Beijing,China: A case study with the WRF-Chem model |
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| Institution: | 1. Beijing Weather Modification Office, Beijing 100089, China;2. Key Laboratory of Aerosol Science and Technology, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710049, China;3. National Center for Atmospheric Research, Boulder, CO, USA;1. Shanghai Meteorological Service, Shanghai 200135, China;2. NOAA Earth System Research Laboratory (ESRL), Boulder, Colorado, USA;1. Ricerca sul Sistema Energetico (RSE S.p.A.), via Rubattino 54, Milano, Italy;2. Center of Excellence “SPACE-SI”, Aškerčeva 12, Ljubljana, Slovenia;3. University of Ljubljana, Faculty of Mathematics and Physics, Jadranska 19, Ljubljana, Slovenia;4. Department of Physical and Chemical Sciences, Center of Excellence for the Forecast of Severe Weather (CETEMPS), University of L''Aquila, L''Aquila, Italy;5. Karlsruher Institut für Technologie (KIT), IMK-IFU, Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen, Germany;6. Zentralanstalt für Meteorologie und Geodynamik, ZAMG, Hohe Warte 38, 1190 Vienna, Austria;7. Environmental Software and Modelling Group, Computer Science School – Technical University of Madrid, Campus de Montegancedo, Boadilla del Monte-28660, Madrid, Spain;8. NOAA Earth System Research Laboratory, Global System Division, 325 Broadway, Boulder, CO, USA;1. Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27606, USA;2. Collaborative Innovation Center for Regional Environmental Quality, Beijing 100084, China;3. Department of Environmental Engineering, Hebei University of Engineering, Handan, Hebei 056038, China;4. Center for Earth System Science, Tsinghua University, Beijing 100084, China;5. The School of Environment, Tsinghua University, Beijing 100084, China;1. Department of Marine, Earth, and Atmospheric Science, North Carolina State University, Campus Box 8208, Raleigh, NC 27695, USA;2. Department of Air Quality and Environmental Management, Clark County, NV 89118, USA;3. National Oceanic and Atmospheric Administration (NOAA), Earth System Research Laboratory, Boulder, USA |
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| Abstract: | The causes and variability of a heavy haze episode in the Beijing region was analyzed. During the episode, the PM2.5 concentration reached a peak value of 450 μg/kg on January 18, 2013 and rapidly decreased to 100 μg/kg on January 19, 2013, characterizing a large variability in a very short period. This strong variability provides a good opportunity to study the causes of the haze formation. The in situ measurements (including surface meteorological data and vertical structures of the winds, temperature, humidity, and planetary boundary layer (PBL)) together with a chemical/dynamical regional model (WRF-Chem) were used for the analysis. In order to understand the rapid variability of the PM2.5 concentration in the episode, the correlation between the measured meteorological data (including wind speed, PBL height, relative humidity, etc.) and the measured particle concentration (PM2.5 concentration) was studied. In addition, two sensitive model experiments were performed to study the effect of individual contribution from local emissions and regional surrounding emissions to the heavy haze formation. The results suggest that there were two major meteorological factors in controlling the variability of the PM2.5 concentration, namely, surface wind speed and PBL height. During high wind periods, the horizontal transport of aerosol particles played an important role, and the heavy haze was formed when the wind speeds were very weak (less than 1 m/s). Under weak wind conditions, the horizontal transport of aerosol particles was also weak, and the vertical mixing of aerosol particles played an important role. As a result, the PBL height was a major factor in controlling the variability of the PM2.5 concentration. Under the shallow PBL height, aerosol particles were strongly confined near the surface, producing a high surface PM2.5 concentration. The sensitivity model study suggests that the local emissions (emissions from the Beijing region only) were the major cause for the heavy haze events. With only local emissions, the calculated peak value of the PM2.5 concentration was 350 μg/kg, which accounted for 78% of the measured peak value (450 μg/kg). In contrast, without the local emissions, the calculated peak value of the PM2.5 concentration was only 100 μg/kg, which accounted for 22% of the measured peak value. |
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| Keywords: | Causes of heavy haze Planetary boundary layer (PBL) WRF-Chem model |
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