Synoptic circulation pattern and boundary layer structure associated with PM2.5 during wintertime haze pollution episodes in Shanghai

Ning, Liu; Zhang, Sha; Liu, Chaoshun; Guo, Jianping

doi:10.1016/j.atmosres.2019.06.001

Cited by 76 publications

(32 citation statements)

References 63 publications

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“…Nevertheless, with constant volumes and composition of emissions, fluctuations in the level of air pollution occur under the influence of the conditions of transport and dispersion of impurities, i.e., depend on the distribution of temperatures with height, wind speed and direction, the intensity of solar radiation and air humidity, the amount and duration of precipitation, and air temperature. Unfavorable meteorological conditions contributing to the accumulation of harmful pollutants in the surface layer of the atmosphere (calm, fog, dangerous wind direction, and speed) can increase the concentration of harmful ones (Liu et al 2019 ; Wang et al 2020 ). Therefore, for a more in-depth understanding of the impact of weather conditions on the concentration of pollutants in the future, it is necessary to conduct a full study.…”

Section: Resultsmentioning

confidence: 99%

Air Quality Changes in Shanghai, China, and the Surrounding Urban Agglomeration During the COVID-19 Lockdown

Filonchyk

Peterson

2020

J geovis spat anal

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COVID-2019 (COronaVIrus Disease 2019), discovered at the end of December 2019, has spread around the world, becoming a pandemic. To prevent its spread, many governments implemented strict lockdown measures, including the closure of factories and limitations on travel. These measures led to a decrease in human activity, affecting air pollutant emissions. This study evaluates air quality during the partial lockdown of Shanghai, the largest city in China, and the broader Yangtze River Delta region. It was found that daily concentrations of PM 2.5, PM 10 , SO 2 , NO 2 , and CO during the lockdown period were reduced by 9%, 77%, 31.3%, 60.4%, and 3% respectively, compared to the same period in 2019. Even with decreasing concentrations of PM 2.5 and PM 10 , the overall values are still more than four times higher for the lockdown period than the World Health Organization (WHO) recommends for safe concentrations (10 μg/m 3 and 20 μg/m 3). This indicates the existence of other background sources that continue to make a significant contribution to air pollution in the region even with severe reductions in human activity. This study may be used to guide environmental policy, as it demonstrates to what extent the control of pollution sources can improve air quality.

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Section: Resultsmentioning

confidence: 99%

Air Quality Changes in Shanghai, China, and the Surrounding Urban Agglomeration During the COVID-19 Lockdown

Filonchyk

Peterson

2020

J geovis spat anal

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“…It needs to be noted that the PBLH values measured with the CL51 ceilometer in our study are relatively low, likely due to high aerosol loadings that affect the backscatter signals (Tang et al, 2015). As detailed in the supporting information Text S1, large biases have been found for PBLH values measured by different methods, including radiosonde, ground‐based lidar, and Cloud‐Aerosol Lidar with Orthogonal Polarization (CALIOP) (Guo et al, 2019; Ho et al, 2015; Kim et al, 2008; Korhonen et al, 2014; Liu et al, 2015, Liu et al, 2019; Su et al, 2018; Zhang et al, 2016).…”

Section: Methodsmentioning

confidence: 99%

Puzzling Haze Events in China During the Coronavirus (COVID‐19) Shutdown

Chang

Huang

et al. 2020

Geophysical Research Letters

182

146

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It is a puzzle as to why more severe haze formed during the New Year Holiday in 2020 (NYH-20), when China was in an unprecedented state of shutdown to contain the coronavirus (COVID-19) outbreak, than in 2019 (NYH-19). We performed a comprehensive measurement and modeling analysis of the aerosol chemistry and physics at multiple sites in China (mainly in Shanghai) before, during, and after NYH-19 and NYH-20. Much higher secondary aerosol fraction in PM 2.5 were observed during NYH-20 (73%) than during NYH-19 (59%). During NYH-20, PM 2.5 levels correlated significantly with the oxidation ratio of nitrogen (r 2 = 0.77, p < 0.01), and aged particles from northern China were found to impede atmospheric new particle formation and growth in Shanghai. A markedly enhanced efficiency of nitrate aerosol formation was observed along the transport pathways during NYH-20, despite the overall low atmospheric NO 2 levels. Plain Language Summary In China, there are multiple cases (e.g., the 2008 Summer Olympics in Beijing and the 2010 World Expo in Shanghai) when combustion-related emissions (e.g., NO x) were actively, and successfully, reduced to transiently improve air quality. During the extended Chinese Lunar New Year holiday in 2020 (between 24 January and 10 February), whole China was in an unprecedented state of shutdown, because most people were contained in their homes to reduce the spread of the novel coronavirus disease (COVID-19). Mobility, energy demand, and industrial output remained far below their normal levels. Nevertheless, widespread haze pollution still occurred over Eastern China. To elucidate haze formation mechanisms, we performed comprehensive and continuous measurements of aerosol chemistry and physics in and out of Shanghai before, during, and after the Chinese New Year Holiday in 2019 and 2020, respectively. We argue that the synergistic effects of long-range transport and atmospheric chemistry leading to the efficient conversion of NO x to particulate nitrate were the key of haze formation during the Chinese New Year Holiday of the COVID-19 outbreak in Shanghai.

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“…Because of the increasing energy consumption associated with rapid urbanization and industrialization, many regions of China, especially megacities and city clusters in coastal eastern China, have experienced high levels of air pollution (He et al, 2002;Chan and Yao, 2008;Tie and Cao, 2009;He et al, 2013;Ding et al, 2016a;Zhao et al, 2018;Barkjohn et al, 2020). In these regions, fine particular matter (PM2.5; particles with an aerodynamic diameter of 2.5 microns or lower in ambient air) often attains extremely high concentrations during the winter haze period (Ding et al 2013a;Huang et al, 2014;Guo et al, 2014;Zhang et al, 2014;Chen et al, 2017;Ma et al, 2017;Liu et al, 2019). High levels of air pollution can significantly modify the weather by changing air temperature, cloud conditions, and even precipitation (Banta et al, 1998, Fiore et al, 2002, Ding et al, 2013b, Huang et al, 2016, Karle et al, 2020.…”

Section: Accepted Manuscript Introductionmentioning

confidence: 99%

Observed Interactions Among Haze, Fog and Atmospheric Boundary Layer during a Haze-fog Episode in the Yangtze River Delta Region, Eastern China

Zou

Sun

et al. 2021

Aerosol Air Qual. Res.

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A severe haze-fog episode occurred in the Yangtze River Delta region of eastern China during 22-30 November, 2018. In this period, the PM2.5 mass concentration and meteorological parameters at the surface were collected at the Station for Observing Regional Processes of the Earth System site in Nanjing. The vertical distributions of PM2.5, humidity and potential temperature below 500 m were observed simultaneously by an unmanned aerial vehicle, and the profile of potential temperature at 1400 local standard time on each day was also observed by radiosonde at the same site. During the first four days, the PM2.5 mass concentration increased, the maximum convective planetary boundary layer height (CBLH) decreased, and the air humidity increased. These are favorable conditions for fog formation. In the latter five days, fog formed on four days, with a lowering of the CBLH and a further increase in PM2.5 mass concentration. We found that the fog top cooling induced a potential temperature jump (i.e., sharp increase of potential temperature) with much warmer temperatures above the cloud top cooling and that this particular thermal structure was maintained until the end of the fog period, which significantly suppressed the daytime development of the planetary boundary layer after fog dissipation. The fog-induced reduction of the CBLH further increased the PM2.5 mass concentration. We also found that the wet deposition of fog on PM2.5 was negligible. The scavenging effect of fog on aerosols only acts during a fog period. When the fog dissipates, the aerosols are liberated from the fog droplets to the atmosphere.

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Synoptic circulation pattern and boundary layer structure associated with PM2.5 during wintertime haze pollution episodes in Shanghai

Cited by 76 publications

References 63 publications

Air Quality Changes in Shanghai, China, and the Surrounding Urban Agglomeration During the COVID-19 Lockdown

Air Quality Changes in Shanghai, China, and the Surrounding Urban Agglomeration During the COVID-19 Lockdown

Puzzling Haze Events in China During the Coronavirus (COVID‐19) Shutdown

Observed Interactions Among Haze, Fog and Atmospheric Boundary Layer during a Haze-fog Episode in the Yangtze River Delta Region, Eastern China

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