Abstract. Atmospheric aerosols scatter or absorb a fraction of the
incoming solar radiation to cool or warm the atmosphere, decreasing surface
temperature and altering atmospheric stability to further affect the
dispersion of air pollutants in the planetary boundary layer (PBL). In the
present study, simulations during a persistent and heavy haze pollution
episode from 5 December 2015 to 4 January 2016 in the North China Plain
(NCP) were performed using the Weather Research and
Forecasting model with Chemistry (WRF-Chem) to comprehensively quantify
contributions of aerosol shortwave radiative feedback (ARF) to near-surface
(around 15 m above the ground surface) PM2.5 mass concentrations. The
WRF-Chem model generally performs well in simulating the temporal variations
and spatial distributions of air pollutants concentrations compared to
observations at ambient monitoring sites in the NCP, and the simulated
diurnal variations of aerosol species are also consistent with the
measurements in Beijing. Additionally, the model simulates the aerosol
radiative properties, the downward shortwave flux, and the PBL height
against observations in the NCP well. During the episode, ARF deteriorates the
haze pollution, increasing the near-surface PM2.5 concentrations in
the NCP by 10.2 µg m−3 or with a contribution of 7.8 % on
average. Sensitivity studies have revealed that high loadings of PM2.5
attenuate the incoming solar radiation reaching the surface to cool the
low-level atmosphere, suppressing the development of the PBL, decreasing the surface
wind speed, further hindering the PM2.5 dispersion, and consequently
exacerbating the haze pollution in the NCP. Furthermore, when the
near-surface PM2.5 mass concentration increases from around 50 to
several hundred µg m−3, ARF contributes to the near-surface
PM2.5 by more than 20 % during daytime in the NCP, substantially
aggravating the heavy haze formation. However, when the near-surface
PM2.5 concentration is less than around 50 µg m−3, ARF
generally reduces the near-surface PM2.5 concentration due to the
consequent perturbation of atmospheric dynamic fields.
Improved empirical models for estimating surface direct and diffuse solar radiation at monthly and daily level: A case study in North China
