Investigation of the atmospheric boundary layer during an unexpected summertime persistent severe haze pollution period in Beijing

Abstract. The study and control of air pollution need to detect the structure of atmospheric boundary layer (ABL) in order to understand the mechanism of interaction between atmospheric boundary layer and air pollution. However, when extreme pollution occurs, the detection of atmospheric boundary layer structure is very scarce. Beijing, the capital of China, has experienced a severe haze pollution in December 2016. The city issued its first red air pollution warning of this year (the highest PM2.5 concentration was later monitored to exceed 450 μg m−3). In this paper, the vertical profiles of wind, temperature, humidity and extinction coefficient (reflecting aerosol concentration), as well as ABL heights and turbulence quantities under heavy haze pollution are analyzed, with collected data from Lidar, wind profile radar (WPR), radiosonde, 325-meter meteorological tower (equipped with 7-layer supersonic anemometer and 15-layer low frequency wind, temperature and humidity sensors) and some other ground observations. ABL heights obtained by three different methods based on Lidar extinction coefficient data (Hc) are compared with the heights calculated from radiosonde temperature data (Hθ) and from WPR wind speed data (Hu). The results show that increase of water vapor has greatly promoted the hygroscopic growth of aerosols, the corresponding extinction coefficients also increased significantly. The PBL heights Hθ and Hu of heavy haze pollution day were generally lower than those of clean day, but Hc increased. Turbulent activities were great inhibited during haze pollution, time changes of both friction velocity (u*) and turbulent kinetic energy (TKE) have obvious inverse correlation with that of PM2.5. The results of this paper could provide some reference for the parameterization of the boundary layer height and turbulent diffusion process in the numerical model of severe air pollution.

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Multiple technical observations of the atmospheric boundary layer structure of a red-alert haze episode in Beijing

Atmospheric Measurement Techniques ◽

10.5194/amt-12-4887-2019 ◽

2019 ◽

Vol 12 (9) ◽

pp. 4887-4901 ◽

Cited By ~ 5

Author(s):

Yu Shi ◽

Fei Hu ◽

Guangqiang Fan ◽

Zhe Zhang

Keyword(s):

Boundary Layer ◽

Air Pollution ◽

Atmospheric Boundary Layer ◽

Extinction Coefficient ◽

Layer Structure ◽

Heat Fluxes ◽

Sensible Heat ◽

Boundary Layer Structure ◽

Haze Pollution ◽

Heavy Pollution

Abstract. The study and control of air pollution involves measuring the structure of the atmospheric boundary layer (ABL) to understand the mechanisms of the interactions occurring between the atmospheric boundary layer and air pollution. Beijing, the capital of China, experienced heavy haze pollution in December 2016, and the city issued its first red-alert air pollution warning of the year (the highest PM2.5 concentrations were later found to exceed 450 µg m−3). In this paper, the vertical profiles of wind, temperature, humidity and the extinction coefficient (reflecting aerosol concentrations), as well as ABL heights and turbulence quantities under heavy haze pollution conditions, are analyzed, with data collected from lidar, wind profile radar (WPR), radiosondes, a 325 m meteorological tower (equipped with a 7-layer ultrasonic anemometer and 15-layer low-frequency wind, temperature, and humidity sensors) and ground observations. The ABL heights obtained by three different methods based on lidar extinction coefficient data (Hc) are compared with the heights calculated from radiosonde temperature data (Hθ), and their correlation coefficient can reach 72 %. Our results show that Hθ measured on heavy haze pollution days was generally lower than that measured on clean days without pollution, but Hc increased from clean to heavy pollution days. The time changes in friction velocity (u*) and turbulent kinetic energy (TKE) were clearly inversely correlated with PM2.5 concentration. Momentum and heat fluxes varied very little with altitude. The nocturnal sensible heat fluxes close to the Earth surface always stay positive. In the daytime of the haze pollution period, sensible heat fluxes were greatly reduced within 300 m of the ground. These findings will deepen our understanding of the boundary layer structure under heavy pollution conditions and improve the boundary layer parameterization in numerical models.

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The impacts of the atmospheric boundary layer on regional haze in North China

npj Climate and Atmospheric Science ◽

10.1038/s41612-021-00165-y ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Qianhui Li ◽

Hongsheng Zhang ◽

Xuhui Cai ◽

Yu Song ◽

Tong Zhu

Keyword(s):

Boundary Layer ◽

Spatial Distribution ◽

Atmospheric Boundary Layer ◽

North China ◽

Inversion Layer ◽

Stable Stratification ◽

Convective Boundary ◽

The North ◽

Haze Pollution ◽

Weak Wind

AbstractAn intensive atmospheric boundary layer (ABL) experiment was conducted simultaneously at six stations arranged in a cross shape on the North China Plain (NCP) from 26 November to 26 December 2019. The impacts of the regional ABL structure on heavy haze pollution and the relationship between the ABL height and aerosol accumulation layer (AAL) depth were discussed. Bouts of downdrafts generate a persistent descending elevated inversion layer, helping the maintenance and exacerbation of haze pollution. Continuous weak wind layers contribute to the pollutants accumulation, and low-level jets promote the removal of air pollutants. The unique landform conditions of the NCP are reflected in its regional ABL structure and further affect the spatial distribution of haze pollution. Due to the drainage flow and strong downdrafts, the western stations near the mountains have a colder surface and warmer upper air masses, resulting in a more stable stratification and worse diffusion conditions; these stations also experience a thicker weak wind layer caused by increased friction. Thus, the spatial distribution of haze is heavier in the west and lighter in the east. The convective boundary layer (CBL) height declines evidently during haze episodes, usually lower than 560 m. Furthermore, as the vertical distribution of aerosols is mainly influenced by daytime thermal turbulence and maintained at night, it is appropriate to determine the CBL height using the AAL depth. However, the AAL depth is not consistent with the stable boundary layer height due to the influence of the residual layer at night.

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