scholarly journals Haze pollution under a high atmospheric oxidization capacity in summer in Beijing: insights into formation mechanism of atmospheric physicochemical processes

2020 ◽  
Vol 20 (8) ◽  
pp. 4575-4592 ◽  
Author(s):  
Dandan Zhao ◽  
Guangjing Liu ◽  
Jinyuan Xin ◽  
Jiannong Quan ◽  
Yuesi Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Particulate Matter ◽  
Potential Temperature ◽  
Equivalent Diameter ◽  
Pollution Transport ◽  
Aerosol Formation ◽  
Near Surface ◽  
Physicochemical Processes ◽  
Haze Pollution

Abstract. Under a high atmospheric oxidization capacity, the synergistic effect of the physicochemical processes in the atmospheric boundary layer (ABL) caused summer haze pollution in Beijing. The southern and southwestern areas, generally 60–300 km away from Beijing, were seriously polluted in contrast to Beijing, which remained clean. Southerly winds moving faster than 20–30 km h−1 since the early morning primarily caused haze pollution initiation. The PM2.5 (particulate matter with a dynamic equivalent diameter smaller than 2.5 µm) level increased to 75 µg m−3 over several hours during the daytime, which was simultaneously affected by the ABL structure. Additionally, the O3 concentration was quite high during the daytime (250 µg m−3), corresponding to a high atmospheric oxidation capacity. Much sulfate and nitrate were produced through active atmospheric chemical processes, with sulfur oxidation ratios (SORs) up to ∼0.76 and nitrogen oxidation ratios (NORs) increasing from 0.09 to 0.26, which further facilitated particulate matter (PM) level enhancement. However, the increase in sulfate was mainly linked to southerly transport. At midnight, the PM2.5 concentration sharply increased from 75 to 150 µg m−3 over 4 h and remained at its highest level until the next morning. Under an extremely stable ABL structure, secondary aerosol formation dominated by nitrate was quite intense, driving the haze pollution outbreak. The PM levels in the southern and southeastern areas of Beijing were significantly lower than those in Beijing at this time, even below air quality standards; thus, the contribution of pollution transport had almost disappeared. With the formation of a nocturnal stable boundary layer (NSBL) at an altitude ranging from 0–0.3 km, the extremely low turbulence kinetic energy (TKE) ranging from 0 to 0.05 m2 s−2 inhibited the spread of particles and moisture, ultimately resulting in elevated near-surface PM2.5 and relative humidity (∼90 %) levels. Due to the very high humidity and ambient oxidization capacity, NOR rapidly increased from 0.26 to 0.60, and heterogeneous hydrolysis reactions at the moist particle surface were very notable. The nitrate concentration steeply increased from 11.6 to 57.8 µg m−3, while the sulfate and organics concentrations slightly increased by 6.1 and 3.1 µg m−3, respectively. With clean and strong winds passing through Beijing, the stable ABL dissipated with the potential temperature gradient becoming negative and the ABL height (ABLH) increasing to ∼2.5 km. The high turbulence activity with a TKE ranging from 3 to 5 m2 s−2 notably promoted pollution diffusion. The self-cleaning capacity of the atmosphere is commonly responsible for air pollution dispersion. However, reducing the atmospheric oxidization capacity, through strengthening collaborative control of nitrogen oxide (NOx) and volatile organic compounds (VOCs), as well as continuously deepening regional joint air pollution control, is urgent.

scholarly journals The haze pollution under strong atmospheric oxidization capacity in summer in Beijing: Insights into the formation mechanism of atmospheric physicochemical process

2020 ◽  
Author(s):  
Dandan Zhao ◽  
Guangjing Liu ◽  
Jinyuan Xin ◽  
Jiannong Quan ◽  
Yuesi Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Potential Temperature ◽  
Particle Surface ◽  
Physicochemical Process ◽  
Joint Control ◽  
Pollution Transport ◽  
The South ◽  
Haze Pollution ◽  
Oxidation Ratio

Abstract. Under strong atmospheric oxidization capacity, haze pollution in the summer of Beijing was the result of the synergistic effect of physicochemical process in the atmospheric boundary layer (ABL). The south/southwest areas generally ~ 60–300 km far away from Beijing were seriously polluted, in contrast to a clean situation in Beijing. The southerly winds moving more than ~ 20–30 km h−1 since early morning primarily caused the initiation of haze pollution. The PM2.5 level increased to 75 μg m−3 in several hours at daytime, which was simultaneously affected by the ABL structure. Additionally, the O3 concentration was quite high at daytime (250 μg m−3), corresponding to a strong atmospheric oxidation capacity. Numerous sulfate and nitrate were formed through active atmospheric chemical processes, with sulfur oxidation ratio (SOR) up to ~ 0.76 and nitrogen oxidation ratio (NOR) increasing from 0.09 to 0.26, which further facilitated the particulate matter (PM) level rising. Even so, the increase in sulfate was mainly linked by southerly transport. At midnight, the PM2.5 concentration sharply increased from 75 μg m−3 to 150 μg m−3 in 4 hours and stayed the highest level till the next morning. With the premise of an extremely stable ABL structure, the formation of secondary aerosols dominated by nitrate was quite intense, driving the outbreak of haze pollution. PM levels in the south/southeast of Beijing were significantly lower than that in Beijing over this time, even below air quality standards, thus, the contribution of pollution transport was almost gone. With the formation of nocturnal stable boundary layer of 0–0.3 km altitude, the extremely low turbulence kinetic energy (TKE) of 0–0.05 m2 s−2 inhibited the spread of particles and moisture, ending up with elevated levels of PM2.5 and relative humidity (~ 90 %) near the surface. Under quite high humidity and strong ambient oxidization capacity, the NOR rapidly increased from 0.26 to 0.60 and heterogeneous hydrolysis reactions at the moist particle surface were very significant. The nitrate concentration explosively increased from 11.6 μg m−3 to 57.8 μg m−3, while the concentrations of sulfate and organics slightly increased by 6.1 μg m−3 and 3.1 μg m−3, respectively. With clean & strong winds passing through Beijing, the stable ABL was broken with potential temperature gradient turning to negative and ABL heights increasing to ~ 2.5 km. The strong turbulence activity with TKE of ~ 3–5 m2 s−2 notably promoted the pollution diffusion. The self-cleaning capacity of the atmosphere is always responsible for the dispersion of air pollution. Even so, reducing atmospheric oxidization capacity such as strengthening the collaborative control of nitrogen oxide (NOx) and volatile organic compounds (VOCs) was urgent, as well as continuously deepening regional joint control of air pollution.

scholarly journals Dome effect of black carbon and its key influencing factors: A one-dimensional modelling study

2017 ◽  
Author(s):  
Zilin Wang ◽  
Xin Huang ◽  
Aijun Ding
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Black Carbon ◽  
Rural Areas ◽  
Land Surface ◽  
Critical Role ◽  
Aerosol Layer ◽  
Near Surface ◽  
Haze Pollution ◽  
The Impact

Abstract. Black carbon (BC) has been identified to play a critical role in aerosol-planet boundary layer (PBL) interaction and further deterioration of near-surface air pollution in megacities, which has been named as its dome effect. However, the impacts of key factors that influence this effect, such as the vertical distribution and aging processes of BC, and also the underlying land surface, have not been quantitatively explored yet. Here, based on available in-situ measurements of meteorology and atmospheric aerosols together with the meteorology-chemistry online coupled model, WRF-Chem, we conduct a set of parallel simulations to quantify the roles of these factors in influencing the BC's dome effect and surface haze pollution, and discuss the main implications of the results to air pollution mitigation in China. We found that the impact of BC on PBL is very sensitive to the altitude of aerosol layer. The upper level BC, especially those near the capping inversion, is more essential in suppressing the PBL height and weakening the turbulence mixing. The dome effect of BC tends to be significantly intensified as BC aerosol mixed with scattering aerosols during winter haze events, resulting in a decrease of PBL height by more than 25 %. In addition, the dome effect is more substantial (up to 15 %) in rural areas than that in the urban areas with the same BC loading, indicating an unexpected regional impact of such kind of effect to air quality in countryside. This study suggests that China's regional air pollution would greatly benefit from BC emission reductions, especially those from the elevated sources from the chimneys and also the domestic combustions in rural areas, through weakening the aerosol-boundary layer interactions that triggered by BC.

scholarly journals Dome effect of black carbon and its key influencing factors: a one-dimensional modelling study

2018 ◽  
Vol 18 (4) ◽  
pp. 2821-2834 ◽  
Author(s):  
Zilin Wang ◽  
Xin Huang ◽  
Aijun Ding
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Black Carbon ◽  
Rural Areas ◽  
Land Surface ◽  
Critical Role ◽  
Aerosol Layer ◽  
Near Surface ◽  
Haze Pollution ◽  
The Impact

Abstract. Black carbon (BC) has been identified to play a critical role in aerosol–planetary boundary layer (PBL) interaction and further deterioration of near-surface air pollution in megacities, which has been referred to as the “dome effect”. However, the impacts of key factors that influence this effect, such as the vertical distribution and aging processes of BC, as well as the underlying land surface, have not been quantitatively explored yet. Here, based on available in situ measurements of meteorology and atmospheric aerosols together with the meteorology–chemistry online coupled model WRF-Chem, we conduct a set of parallel simulations to quantify the roles of these factors in influencing the BC dome effect and surface haze pollution. Furthermore, we discuss the main implications of the results to air pollution mitigation in China. We found that the impact of BC on the PBL is very sensitive to the altitude of aerosol layer. The upper-level BC, especially that near the capping inversion, is more essential in suppressing the PBL height and weakening the turbulent mixing. The dome effect of BC tends to be significantly intensified as BC mixed with scattering aerosols during winter haze events, resulting in a decrease in PBL height by more than 15 %. In addition, the dome effect is more substantial (up to 15 %) in rural areas than that in the urban areas with the same BC loading, indicating an unexpected regional impact of such an effect to air quality in countryside. This study indicates that China's regional air pollution would greatly benefit from BC emission reductions, especially those from elevated sources from chimneys and also domestic combustion in rural areas, through weakening the aerosol–boundary layer interactions that are triggered by BC.

scholarly journals Inference of Marine Atmospheric Boundary Layer Moisture and Temperature Structure Using Airborne Lidar and Infrared Radiometer Data

1998 ◽  
Vol 37 (3) ◽  
pp. 308-324 ◽  
Author(s):  
Stephen P. Palm ◽  
Denise Hagan ◽  
Geary Schwemmer ◽  
S. H. Melfi
Keyword(s):  
Boundary Layer ◽  
Atmospheric Boundary Layer ◽  
Potential Temperature ◽  
Airborne Lidar ◽  
Temperature Structure ◽  
Marine Atmospheric Boundary Layer ◽  
Space Technology ◽  
Near Surface ◽  
Surface Moisture ◽  
Infrared Radiometer

Abstract A new technique for retrieving near-surface moisture and profiles of mixing ratio and potential temperature through the depth of the marine atmospheric boundary layer (MABL) using airborne lidar and multichannel infrared radiometer data is presented. Data gathered during an extended field campaign over the Atlantic Ocean in support of the Lidar In-space Technology Experiment are used to generate 16 moisture and temperature retrievals that are then compared with dropsonde measurements. The technique utilizes lidar-derived statistics on the height of cumulus clouds that frequently cap the MABL to estimate the lifting condensation level. Combining this information with radiometer-derived sea surface temperature measurements, an estimate of the near-surface moisture can be obtained to an accuracy of about 0.8 g kg−1. Lidar-derived statistics on convective plume height and coverage within the MABL are then used to infer the profiles of potential temperature and moisture with a vertical resolution of 20 m. The rms accuracy of derived MABL average moisture and potential temperature is better than 1 g kg−1 and 1°C, respectively. The method relies on the presence of a cumulus-capped MABL, and it was found that the conditions necessary for use of the technique occurred roughly 75% of the time. The synergy of simple aerosol backscatter lidar and infrared radiometer data also shows promise for the retrieval of MABL moisture and temperature from space.

scholarly journals Effect of the uncertainty in meteorology on air quality model predictions

Időjárás ◽  
2021 ◽  
Vol 125 (4) ◽  
pp. 625-646
Author(s):  
Zita Ferenczi ◽  
Emese Homolya ◽  
Krisztina Lázár ◽  
Anita Tóth
Keyword(s):  
Air Pollution ◽  
Particulate Matter ◽  
Air Quality ◽  
Weather Prediction ◽  
Horizontal Resolution ◽  
Model System ◽  
Air Quality Model ◽  
Quality Model ◽  
Near Surface ◽  
The Impact

An operational air quality forecasting model system has been developed and provides daily forecasts of ozone, nitrogen oxides, and particulate matter for the area of Hungary and three big cites of the country (Budapest, Miskolc, and Pécs). The core of the model system is the CHIMERE off-line chemical transport model. The AROME numerical weather prediction model provides the gridded meteorological inputs for the chemical model calculations. The horizontal resolution of the AROME meteorological fields is consistent with the CHIMERE horizontal resolution. The individual forecasted concentrations for the following 2 days are displayed on a public website of the Hungarian Meteorological Service. It is essential to have a quantitative understanding of the uncertainty in model output arising from uncertainties in the input meteorological fields. The main aim of this research is to probe the response of an air quality model to its uncertain meteorological inputs. Ensembles are one method to explore how uncertainty in meteorology affects air pollution concentrations. During the past decades, meteorological ensemble modeling has received extensive research and operational interest because of its ability to better characterize forecast uncertainty. One such ensemble forecast system is the one of the AROME model, which has an 11-member ensemble where each member is perturbed by initial and lateral boundary conditions. In this work we focus on wintertime particulate matter concentrations, since this pollutant is extremely sensitive to near-surface mixing processes. Selecting a number of extreme air pollution situations we will show what the impact of the meteorological uncertainty is on the simulated concentration fields using AROME ensemble members.

scholarly journals HTAP_v2.2: a mosaic of regional and global emission grid maps for 2008 and 2010 to study hemispheric transport of air pollution

2015 ◽  
Vol 15 (19) ◽  
pp. 11411-11432 ◽  
Author(s):  
G. Janssens-Maenhout ◽  
M. Crippa ◽  
D. Guizzardi ◽  
F. Dentener ◽  
M. Muntean ◽  
...  
Keyword(s):  
Air Pollution ◽  
Particulate Matter ◽  
Low Income ◽  
Regional Scale ◽  
Global Scale ◽  
Air Pollutant ◽  
Pollutant Emissions ◽  
Pollution Transport ◽  
Data Set ◽  
Per Capita

Abstract. The mandate of the Task Force Hemispheric Transport of Air Pollution (TF HTAP) under the Convention on Long-Range Transboundary Air Pollution (CLRTAP) is to improve the scientific understanding of the intercontinental air pollution transport, to quantify impacts on human health, vegetation and climate, to identify emission mitigation options across the regions of the Northern Hemisphere, and to guide future policies on these aspects. The harmonization and improvement of regional emission inventories is imperative to obtain consolidated estimates on the formation of global-scale air pollution. An emissions data set has been constructed using regional emission grid maps (annual and monthly) for SO2, NOx, CO, NMVOC, NH3, PM10, PM2.5, BC and OC for the years 2008 and 2010, with the purpose of providing consistent information to global and regional scale modelling efforts. This compilation of different regional gridded inventories – including that of the Environmental Protection Agency (EPA) for USA, the EPA and Environment Canada (for Canada), the European Monitoring and Evaluation Programme (EMEP) and Netherlands Organisation for Applied Scientific Research (TNO) for Europe, and the Model Inter-comparison Study for Asia (MICS-Asia III) for China, India and other Asian countries – was gap-filled with the emission grid maps of the Emissions Database for Global Atmospheric Research (EDGARv4.3) for the rest of the world (mainly South America, Africa, Russia and Oceania). Emissions from seven main categories of human activities (power, industry, residential, agriculture, ground transport, aviation and shipping) were estimated and spatially distributed on a common grid of 0.1° × 0.1° longitude-latitude, to yield monthly, global, sector-specific grid maps for each substance and year. The HTAP_v2.2 air pollutant grid maps are considered to combine latest available regional information within a complete global data set. The disaggregation by sectors, high spatial and temporal resolution and detailed information on the data sources and references used will provide the user the required transparency. Because HTAP_v2.2 contains primarily official and/or widely used regional emission grid maps, it can be recommended as a global baseline emission inventory, which is regionally accepted as a reference and from which different scenarios assessing emission reduction policies at a global scale could start. An analysis of country-specific implied emission factors shows a large difference between industrialised countries and developing countries for acidifying gaseous air pollutant emissions (SO2 and NOx) from the energy and industry sectors. This is not observed for the particulate matter emissions (PM10, PM2.5), which show large differences between countries in the residential sector instead. The per capita emissions of all world countries, classified from low to high income, reveal an increase in level and in variation for gaseous acidifying pollutants, but not for aerosols. For aerosols, an opposite trend is apparent with higher per capita emissions of particulate matter for low income countries.

Climatological study of the Boundary-layer air Stagnation Index for China and its relationship with air pollution

2020 ◽  
Author(s):  
Qianqian Huang ◽  
Xuhui Cai ◽  
Jian Wang ◽  
Yu Song ◽  
Tong Zhu
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Weak Link ◽  
Fine Particulate Matter ◽  
Pollution Index ◽  
Climatic Data ◽  
Near Surface ◽  
National Climatic Data Center ◽  
The Us ◽  
Pm2.5 Concentration

<p>The Air Stagnation Index (ASI) is a vital meteorological measure of the atmosphere’s ability to dilute air pollutants. The original metric adopted by the US National Climatic Data Center (NCDC) is found to be not very suitable for China, because the decoupling between the upper and lower atmospheric layers results in a weak link between the near-surface air pollution and upper-air wind speed. Therefore, a new threshold for the ASI–Boundary-layer air Stagnation Index (BSI) is proposed, consisting of daily maximal ventilation in the atmospheric boundary layer, precipitation, and real latent instability. In the present study, the climatological features of the BSI are investigated. It shows that the spatial distribution of the BSI is similar to the ASI; that is, annual mean stagnations occur most often in the northwestern and southwestern basins, i.e., the Xinjiang and Sichuan basins (more than 180 days), and least over plateaus, i.e., the Qinghai–Tibet and Yunnan plateaus (less than 40 days). However, the seasonal cycle of the BSI is changed. Stagnation days under the new metric are observed to be maximal in winter and minimal in summer, which is positively correlated with the air pollution index (API) during 2000–2012. The correlations between the BSI and the concentration of fine particulate matter (PM2.5) during January 2013 and November to December in 2015–2017 of Beijing are also investigated. It shows that the BSI matches the day-by-day variation of PM2.5 concentration very well and is able to catch the haze episodes.</p>

Homogenized Variability of Radiosonde-Derived Atmospheric Boundary Layer Height over the Global Land Surface from 1973 to 2014

2016 ◽  
Vol 29 (19) ◽  
pp. 6893-6908 ◽  
Author(s):  
Xiaoyan Wang ◽  
Kaicun Wang
Keyword(s):  
United States ◽  
Boundary Layer ◽  
Time Series ◽  
Land Surface ◽  
Statistical Significance ◽  
Potential Temperature ◽  
The United States ◽  
Near Surface ◽  
Layer Height ◽  
Boundary Layer Height

Abstract Boundary layer height (BLH) significantly impacts near-surface air quality, and its determination is important for climate change studies. Integrated Global Radiosonde Archive data from 1973 to 2014 were used to estimate the long-term variability of the BLH based on profiles of potential temperature, relative humidity, and atmospheric refractivity. However, this study found that there was an obvious inhomogeneity in the radiosonde-derived BLH time series because of the presence of discontinuities in the raw radiosonde dataset. The penalized maximal F test and quantile-matching adjustment were used to detect the changepoints and to adjust the raw BLH series. The most significant inhomogeneity of the BLH time series was found over the United States from 1986 to 1992, which was mainly due to progress made in sonde models and processing procedures. The homogenization did not obviously change the magnitude of the daytime convective BLH (CBLH) tendency, but it improved the statistical significance of its linear trend. The trend of nighttime stable BLH (SBLH) is more dependent on the homogenization because the magnitude of SBLH is small, and SBLH is sensitive to the observational biases. The global daytime CBLH increased by about 1.6% decade−1 before and after homogenization from 1973 to 2014, and the nighttime homogenized SBLH decreased by −4.2% decade−1 compared to a decrease of −7.1% decade−1 based on the raw series. Regionally, the daytime CBLH increased by 2.8%, 0.9%, 1.6%, and 2.7% decade−1 and the nighttime SBLH decreased significantly by −2.7%, −6.9%, −7.7%, and −3.5% decade−1 over Europe, the United States, Japan, and Australia, respectively.

scholarly journals Multiple technical observations of the atmospheric boundary layer structure of a red warning haze episode in Beijing

2019 ◽  
Author(s):  
Yu Shi ◽  
Fei Hu ◽  
Guangqiang Fan ◽  
Zhe Zhang
Keyword(s):  
Boundary Layer ◽  
Air Pollution ◽  
Atmospheric Boundary Layer ◽  
Extinction Coefficient ◽  
Layer Structure ◽  
Low Frequency ◽  
Inverse Correlation ◽  
Hygroscopic Growth ◽  
Boundary Layer Structure ◽  
Haze Pollution

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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