Abstract
To investigate aerosol radiative effects, the Sun–Sky Radiometer Observation Network (SONET) has performed long-term observations of columnar atmospheric aerosol properties at 20 distributed stations around China. The aerosol direct radiative forcing (RF) and efficiency (RFE, the rate at which the atmosphere is forced per unit of aerosol optical depth) were estimated using radiative transfer model simulations based on the ground-based observations dating back to 2009. Results of multi-year monthly average RF illustrated that: the dust-dominant aerosol population at arid and semi-arid sites exerted moderate cooling effects (−8.0~−31.2 W/m2) at the top and bottom of atmosphere (TOA and BOA); RF at continental background site was very weak (−0.8~−2.9 W/m2); fine-mode dominant aerosols at urban and suburban sites exerted moderate cooling effects (−9.3~−24.1 W/m2) at TOA but more significant cooling effects (−19.4~−50.6 W/m2) at BOA; RF at coastal sites was comparable with values of urban sites (−5.5~−19.5 W/m2 at TOA, and −15.6~−44.6 W/m2 at BOA), owing to combined influences by marine and urban–industrial aerosols. Differences between RFE at TOA and BOA indicated that coarse-mode dominant aerosols at arid, semi-arid, and continental background sites were less efficient to warm the atmosphere; but fine-mode dominant aerosols at urban, suburban, and coastal sites were shown to be more efficient to heat the atmosphere.
Highlights
Aerosol particles in the atmosphere have substantial influences on the radiative equilibrium and energy budget of the Earth–atmosphere system via direct, semi-direct, and indirect effects [1,2]
The highest absolute value of the multi-year average radiative forcing efficiency (RFE) at BOA within Sky Radiometer Observation Network (SONET) was obtained at Shanghai (−65.3 ± 22 W/m2), which agrees with the previous study [14]
The significant direct effects of absorbing and scattering of solar radiation by atmospheric aerosol particles, which are commonly quantified by the aerosol direct radiative forcing (RF), could result in regional and global climate changes
Summary
Aerosol particles in the atmosphere have substantial influences on the radiative equilibrium and energy budget of the Earth–atmosphere system via direct, semi-direct, and indirect effects [1,2]. Extensive studies have reported the long-term trend, monthly, and seasonal variations of aerosol radiative effects over different regions around the world [2,3,4,5,6,7,8,9]. They provided valuable datasets to improve our knowledge of climate changes on the regional and global scales. The local, instantaneous, and short-term (a few days to several months) quantities of aerosol radiative effects could differ dramatically (up to hundreds of W/m2), even with dynamic warming or cooling effects, owing to the spatial and temporal variations of atmospheric aerosols and surrounding conditions [7,12]
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