Abstract
Abstract. Persistent wintertime heavy haze incidents caused by anthropogenic aerosols have repeatedly shrouded North China in recent years, while natural dust from the west and northwest of China also frequently affects air quality in this region. Through continuous observation by a multi-wavelength Raman lidar, here we found that wintertime aerosols in North China are typically characterized by a pronounced vertical stratification, where scattering nonspherical particles (dust or mixtures of dust and anthropogenic aerosols) dominated above the planetary boundary layer (PBL), and absorbing spherical particles (anthropogenic aerosols) prevailed within the PBL. This stratification is governed by meteorological conditions that strong northwesterly winds usually prevailed in the lower free troposphere, and southerly winds dominated in the PBL, producing persistent and intense haze pollution. With the increased contribution of elevated dust to the upper aerosols, the proportion of aerosol and trace gas at the surface in the whole column increased. Model results show that, besides directly deteriorating air quality, the key role of the elevated dust is to depress the development of PBL and weaken the turbulent exchange, mostly by lower level cooling and upper level heating, and it is more obvious during the dissipation stage, thus inhibiting the dissipation of heavy surface anthropogenic aerosols. The interactions of natural dust and anthropogenic aerosols under the unique topography of North China increase the surface anthropogenic aerosols and precursor gases, which may be one of the reasons why haze pollution in North China is heavier than that in other heavily polluted areas in China.
Highlights
Booming industrialization and urbanization in China are releasing large amounts of atmospheric anthropogenic pollutants, especially in the Beijing–Tianjin–Hebei (BTH) and surrounding regions, where the air pollution is the highest in the country (Zhang et al, 2019a, b)
We focused on the transmission, explosive growth, and dissipation of air pollution along with the interactions between aerosol and meteorology in North China
The EXT355 (EXT at 355 nm wavelength) measured via Raman lidar (RL) shows a periodic cycle of 2–5 d, rising rapidly from less than 0.5 km−1 in the early stage of each heavy pollution incident (HPI) to 3–5 km−1 within 1–2 d (Fig. 2)
Summary
Booming industrialization and urbanization in China are releasing large amounts of atmospheric anthropogenic pollutants, especially in the Beijing–Tianjin–Hebei (BTH) and surrounding regions, where the air pollution is the highest in the country (Zhang et al, 2019a, b). Recent studies have shown that the radiative effect of aerosols reduces solar shortwave radiation, increases the strength of the capping inversion, and enhances the stability of the planetary boundary layer (PBL) (Zhong et al, 2018). Such unfavorable meteorological conditions will enhance the explosive growth of surface air pollutants. The CWBF (39.15◦ N, 115.73◦ E) is located 120 km southwest of Beijing and approximately 40 km away from the Baoding urban district It is surrounded by wheat fields, and there are no nearby stationary pollution sources. Combined with Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem) simulations and multi-axis differential optical absorption spectroscopy (MAX-DOAS) observations, the mechanism of dust’s impact on meteorology and air pollution was explored
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