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
ID:
232131
Ref Key:
dong2017atmosphericopposite