ISSN 1000-0526
CN 11-2282/P
Vertical Distributions of Aerosols Under Different Weather Conditions in Beijing
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    Abstract:

    In this study, aerosol (0.1-3.0 μm)vertical distributions of 17 insitu aircraft measurements during 2005 and 2006 springs are analyzed. The 17 flights are carefully selected to exclude dust events, and the analyses are focused on the vertical distributions of aerosol particles associated with anthropogenic activities. The results show that the vertical distributions of aerosol particles are strongly affected by weather and meteorological conditions, and 3 different types of aerosol vertical distributions corresponding to different weather systems are defined in this study. The measurement with a flat vertical gradient and low surface aerosol concentrations is defined as type1; a gradually decrease of aerosols with altitudes and modest surface aerosol concentrations is defined as type2; a sharp vertical gradient (aerosols being strongly depressed in the PBL) with high surface aerosol concentrations is defined as type3. The weather conditions corresponding to the 3 different aerosol types are high pressure, between two high pressures, and low pressure systems (frontal inversions), respectively. The vertical mixing and horizontal transport for the 3 different vertical distributions are analyzed. Under the type1 condition, the vertical mixing and horizontal transport were rapid, leading to a strong dilution of aerosols in both vertical and horizontal directions. As a result, the aerosol concentrations in PBL (planetary boundary layer) were very low, and the vertical distribution was flat. Under the type2 condition, the vertical mixing was strong and there was no strong barrier at the PBL height. The horizontal transport (wind flux) was modest. As a result, the aerosol concentrations were gradually reduced with altitude, with modest surface aerosol concentrations. Under the type3 condition, there was a cold front near the region. As a result, a frontal inversion associated with weak vertical mixing appeared at the top of the inversion layer, forming a very strong barrier to prevent aerosol particles being exchanged from the PBL height to the free troposphere. Therefore, the aerosol particles were strongly depressed in the PBL height, producing high surface aerosol concentrations.

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History
  • Received:November 03,2010
  • Revised:May 24,2011
  • Adopted:
  • Online: October 21,2011
  • Published:

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