Integrated impacts of synoptic forcing and aerosol radiative effect on boundary layer and pollution in the Beijing–Tianjin–Hebei region, China

Abstract

Abstract. Rapid urbanization and industrialization have led to deterioration of air quality in the Beijing–Tianjin–Hebei (BTH) region due to high loadings of PM2.5. Heavy aerosol pollution frequently occurs in winter, in close relation to the planetary boundary layer (PBL) meteorology. To unravel the physical processes that influence PBL structure and aerosol pollution in BTH, this study combined long-term observational data analyses, synoptic pattern classification, and meteorology–chemistry coupled simulations. During the winter of 2017 and 2018, Beijing and Tangshan often experienced heavy PM2.5 pollution simultaneously, accompanied by strong thermal inversion aloft. These concurrences of pollution in different cities were primarily regulated by the large-scale synoptic conditions. Using principal component analysis with geopotential height fields at the 850 hPa level during winter, two typical synoptic patterns associated with heavy pollution in BTH were identified. One pattern is characterized by a southeast-to-north pressure gradient across BTH, and the other is associated with high pressure in eastern China. Both synoptic types feature warmer air temperature at 1000 m a.g.l., which could suppress the development of the PBL. Under these unfavorable synoptic conditions, aerosols can modulate PBL structure through the radiative effect, which was examined using numerical simulations. The aerosol radiative effect can significantly lower the daytime boundary layer height through cooling the surface layer and heating the upper part of the PBL, leading to the deterioration of air quality. This PBL–aerosol feedback is sensitive to the aerosol vertical structure, which is more effective when the synoptic pattern can distribute more aerosols to the upper PBL.

Interaction between aerosol and thermodynamic stability within the PBL during the wintertime over the North China Plain: Aircraft observation and WRF-Chem simulation

“…5. From the perspective of aerosol vertical distribution, the surface air pollution loading is efficiently driven by the thermal structure and stability of the PBL (Miao et al, 2020;Li, Q. et al, 2021b). On 3 January, the prevailing surface south wind leads to a stable stratification, restraining aerosol vertical dispersion In conclusion, the stable stratification related by the prevailing surface south wind limits the PBL development and exacerbates the surface air pollution by restraining the aerosols to the low layer.…”

“…PBLH is not only influenced by the local-scale surface properties (e.g., surface cover types, sensible heat fluxes, latent heat fluxes, etc. ), but also regulated by large-scale synoptic forcing (Hu et al, 2016;Miao et al, 2020). Synoptic conditions can alter the PBL thermodynamic stability through cold or warm advection, thus affecting the aerosol vertical dispersion (Zhang, J. et al, 2012;Ye et al, 2016;Miao et al, 2019).…”

Interaction between aerosol and thermodynamic stability within the planetary boundary layer during wintertime over the North China Plain: aircraft observation and WRF-Chem simulation

“…In addition, the large-scale synoptic patterns disturb the sensitivity of the aerosol-PBL feedback mechanism. PBLH is not only influenced by the local-scale surface properties (surface cover types, sensible heat fluxes, latent heat fluxes, etc) but is also regulated by large-scale synoptic forcing (Hu et al, 2016;Miao et al, 2020). Synoptic conditions can alter the PBL thermodynamic stability through cold or warm advection, thus affecting the aerosol vertical dispersion (J.…”

A new multispectral photometer for monitoring aerosol microphysical, optical, and radiative properties

“…It has a user-friendly instruction system, and most of the components are assembled in a robotic drive platform, which makes the whole system efficient, secure, low cost and highly integrated. By using direct Sun and diffuse-sky radiation measurements, the CW193 not only provides the columnar instantaneous AOD but also gives detailed information on the aerosol characteristics, including, but not limited, to the volume size distribution (VSD), the single scattering albedo (SSA), the asymmetry factor (ASY), and the aerosol direct radiative forcing (ADRF), which are the key input parameters for numerical models (Miao et al, 2020;Stier et al, 2005;Wang et al, 2013). These features make the CW193 a particularly suitable multispectral photometer for monitoring aerosol microphysical, optical, and radiative properties, especially in remote regions without computer availability to fill in the observation gaps.…”