Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 7997-8009, 2017
https://doi.org/10.5194/acp-17-7997-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
30 Jun 2017
Opposite long-term trends in aerosols between low and high altitudes: a testimony to the aerosol–PBL feedback
Zipeng Dong1,2, Zhanqing Li1,3, Xing Yu2, Maureen Cribb3, Xingmin Li2, and Jin Dai2 1State Key Laboratory of Earth Surface Processes and Resource Ecology and College of Global Change and Earth System Science, Beijing Normal University, Beijing, 100875, China
2Meteorological Institute of Shaanxi Province, Xi'an, 710014, China
3Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD 20742, USA
Abstract. Interactions between absorbing aerosols and the planetary boundary layer (PBL) play an important role in affecting air pollution near the surface. In this study, a unique feature of the aerosol–PBL interaction is identified that has important implications in monitoring and combating air pollution. Opposite trends in aerosol loading between the lower and upper PBL are shown on a wide range of timescales and data acquired by various platforms: from a short-term field experiment to decadal satellite observations and multidecadal ground observations in China. A novel method is proposed to obtain the vertical profiles of aerosol loading from passive sensors by virtue of varying elevations. The analyses of visibility, aerosol optical depth, and extinction with different temporal scales exhibit the similar trend, i.e., increasing in the lower atmosphere but decreasing in the upper atmosphere. Integration of the reversal aerosol trend below and above the PBL resulted in a much less change in the column-integrated quantities. The surface cooling effect, together with the change in the heating rate induced by the absorbing aerosol, unevenly modifies the atmospheric temperature profile, causing a more stable atmosphere inside the PBL but a destabilized atmosphere above the PBL. Such a change in the atmospheric stability favors the accumulation of pollutants near the surface and the vertical diffusion of aerosol particles in the upper atmosphere, both of which are consistent with the observed reversal aerosol trends. These findings have multiple implications in understanding and combating air pollution, especially in many developing countries with high emissions of light-absorbing aerosols.

Citation: Dong, Z., Li, Z., Yu, X., Cribb, M., Li, X., and Dai, J.: Opposite long-term trends in aerosols between low and high altitudes: a testimony to the aerosol–PBL feedback, Atmos. Chem. Phys., 17, 7997-8009, https://doi.org/10.5194/acp-17-7997-2017, 2017.
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Short summary
Opposite trends in aerosol loading between the lower and upper planetary boundary layer are found on a wide range of timescales and from different types of data acquired by various platforms in China. The reversal trend is consistent with the strong vertical gradients in the aerosol-induced atmospheric heating rate that unevenly modifies the atmospheric temperature profile and alters the stability differently. The findings have multiple implications in understanding and combating air pollution.
Opposite trends in aerosol loading between the lower and upper planetary boundary layer are...
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