scholarly journals Impacts of black carbon on the formation of advection–radiation fog during a haze pollution episode in eastern China

2019 ◽  
Vol 19 (11) ◽  
pp. 7759-7774 ◽  
Author(s):  
Qiuji Ding ◽  
Jianning Sun ◽  
Xin Huang ◽  
Aijun Ding ◽  
Jun Zou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Eastern China ◽  
Vertical Mixing ◽  
Radiation Fog ◽  
Near Surface ◽  
Pollution Episode ◽  
Haze Pollution ◽  
Bc Aerosols ◽  
The Yrd ◽  
The Impact

Abstract. Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze events. The impact of aerosols on fog formation, yet to be revealed, can be critical in understanding and predicting fog–haze events. In this study, we used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to investigate a heavy fog event during a multiday intense haze pollution episode in early December 2013 in the Yangtze River Delta (YRD) region in eastern China. Using the WRF-Chem model, we conducted four parallel numerical experiments to evaluate the roles of aerosol–radiation interaction (ARI), aerosol–cloud interaction (ACI), black carbon (BC) and non-BC aerosols in the formation and maintenance of the heavy fog event. We find that only when the aerosols' feedback processes are considered can the model capture the haze pollution and the fog event well. And the effects of ARI during the fog–haze episode in early December 2013 played a dominant role, while the effects of ACI were negligible. Furthermore, our analyses show that BC was more important in inducing fog formation in the YRD region on 7 December than non-BC aerosols. The dome effect of BC leads to an increase in air moisture over the sea by reducing PBLH and weakening vertical mixing, thereby confining more water vapor to the near-surface layer. The strengthened daytime onshore flow by a cyclonic wind anomaly, induced by contrast temperature perturbation over land and sea, transported moister air to the YRD region, where the suppressed PBLH and weakened daytime vertical mixing maintained the high moisture level. Then heavy fog formed due to the surface cooling at night. This study highlights the importance of anthropogenic emissions in the formation of advection–radiation fog in the polluted coastal areas.

scholarly journals Impacts of black carbon on the formation of advection-radiation fog during a haze pollution episode in eastern China

2019 ◽  
Author(s):  
Qiuji Ding ◽  
Jianning Sun ◽  
Xin Huang ◽  
Aijun Ding ◽  
Jun Zou ◽  
...  
Keyword(s):  
Black Carbon ◽  
Eastern China ◽  
Vertical Mixing ◽  
Radiation Fog ◽  
Haze Event ◽  
Pollution Episode ◽  
Haze Pollution ◽  
Bc Aerosols ◽  
The Yrd ◽  
The Impact

Abstract. Aerosols can not only participate in fog formation by acting as condensation nuclei of droplets but also modify the meteorological conditions such as air temperature and moisture, planetary boundary layer height (PBLH) and regional circulation during haze event. The impact of aerosols on fog formation, yet to be revealed, can be critical in understanding and predicting of fog-haze event. In this study, we used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) to investigate a heavy fog event during a multiday intense haze pollution episode in early December 2013 in the Yangtze River Delta (YRD) region in eastern China. Using the WRF-Chem model, we conducted four parallel numerical experiments to evaluate the roles of aerosol-radiation interaction (ARI), aerosol-cloud interaction (ACI), black carbon (BC) and none BC (non-BC) aerosols in the formation and maintenance of the heavy fog event. Only when the aerosols' feedback processes are considered can the model well capture the haze pollution and the fog event. We find that the ARI dominates this fog-haze episode while the effects of ACI are negligible. Our analyses shows that BC plays a more important role in fog formation than non-BC aerosols. The dome effect of BC leads to an increase of air moisture over the sea by reducing PBLH and weakening vertical mixing, thereby confining more water vapor in the near-surface layer. The strengthened daytime onshore flow by a cyclonic wind anomaly, induced by contrast temperature perturbation over land and sea, transports moister air to the YRD region, where the suppressed PBLH and weakened daytime vertical mixing maintain the high moisture level. Then the heave fog forms due to the surface cooling at night in this region. This study highlights the importance of anthropogenic emissions in the formation of advection-radiation fog in the polluted coastal areas.

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 Transport, mixing, and feedback of dust, biomass burning and anthropogenic pollutants in eastern Asia: A case study

2018 ◽  
Author(s):  
Derong Zhou ◽  
Ke Ding ◽  
Xin Huang ◽  
Lixia Liu ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Biomass Burning ◽  
Eastern China ◽  
Measurement Data ◽  
Climate Impacts ◽  
Pollution Sources ◽  
Eastern Asia ◽  
Near Surface ◽  
Pollution Episode ◽  
The Yrd

Abstract. Anthropogenic fossil fuel (FF) combustion, biomass burning (BB) and desert dust are main sources of air pollutants around the globe. The emission of the three sources in Asia are all very intensive and their influences on air quality is very important, especially in spring. In this study, we investigate the vertical distribution, transport characteristics, source contribution, and meteorological feedback of the dust, BB and FF aerosols in a unique pollution episode occurred in eastern Asia based on various measurement data and modelling methods. Ground-based observations indicated a persistent pollution episode dramatically changing from secondary fine particulate pollution to dust pollution in late March 2015 over the Yangtze River Delta (YRD) region, eastern China. The online-coupled meteorology–chemistry–aerosol modelling together with Lagrangian particle dispersion simulations were conducted to investigate the vertical structure, transport characteristics and mechanisms of the multi-scale, multi-source, and multi-day air pollution episode. The regional polluted continental aerosols mainly accumulated near surface by local anthropogenic emissions mixed with dust aerosols, downwash from the upper planetary boundary layer (PBL) and middle/lower troposphere (MLT), and further transported downwardly by large-scale cold fronts and warm conveyor belts. BB smoke from the Southeast Asia, mainly from forest burning in Indochina, were transported by westerlies around the altitude of 3 km from southern China to eastern China, further mixed with dust and FF aerosols in eastern China and experienced long-range transport over the subtropical Pacific Ocean. The three pollutant sources could all transport to eastern China, especially the YRD region around the latitude of 30° N, caused a structure of multi-layer pollutants and well mixed pollutants there. These solar absorption aerosols from FF, BB and dust could also cause significant feedback with MLT meteorology and then enhance local anthropogenic pollution. This study highlights the importance of intensive vertical measurement in the eastern China and the downwind Pacific Ocean with a focus of understanding the complex physical and chemical processes of various pollution sources, and also raises the needs of quantitative understanding of environmental and climate impacts of these pollution sources in regional even global scales.

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 Transport, mixing and feedback of dust, biomass burning and anthropogenic pollutants in eastern Asia: a case study

2018 ◽  
Vol 18 (22) ◽  
pp. 16345-16361 ◽  
Author(s):  
Derong Zhou ◽  
Ke Ding ◽  
Xin Huang ◽  
Lixia Liu ◽  
Qiang Liu ◽  
...  
Keyword(s):  
Air Pollution ◽  
Biomass Burning ◽  
Southern China ◽  
Eastern China ◽  
Measurement Data ◽  
Lower Troposphere ◽  
Climate Impacts ◽  
Eastern Asia ◽  
Pollution Episode ◽  
The Yrd

Abstract. Anthropogenic fossil fuel (FF) combustion, biomass burning (BB) and desert dust are the main sources of air pollutants around the globe but are particularly intensive and important for air quality in Asia in spring. In this study, we investigate the vertical distribution, transport characteristics, source contribution and meteorological feedback of these aerosols in a unique pollution episode that occurred in eastern Asia based on various measurement data and modeling methods. In this episode, the Yangtze River Delta (YRD) in eastern China experienced persistent air pollution, dramatically changing from secondary fine particulate pollution to dust pollution in late March 2015. The Eulerian and Lagrangian models were conducted to investigate the vertical structure, transport characteristics and mechanisms of the multi-scale, multisource and multiday air pollution episode. The regional polluted continental aerosols mainly accumulated near the surface, mixed with dust aerosol downwash from the upper planetary boundary layer (PBL) and middle–lower troposphere (MLT), and further transported by large-scale cold fronts and warm conveyor belts. BB smoke from Southeast Asia was transported by westerlies around the altitude of 3 km from southern China, was further mixed with dust and FF aerosols in eastern China and experienced long-range transport over the Pacific. These pollutants could all be transported to the YRD region and cause a structure of multilayer pollution there. These pollutants could also cause significant feedback with MLT meteorology and then enhance local anthropogenic pollution. This study highlights the importance of intensive vertical measurement in eastern China and the downwind Pacific Ocean and raises the need for quantitative understanding of environmental and climate impacts of these pollution sources.

scholarly journals Fire emission heights in the climate system – Part 2: Impact on transport, black carbon concentrations and radiation

2015 ◽  
Vol 15 (13) ◽  
pp. 7173-7193 ◽  
Author(s):  
A. Veira ◽  
S. Kloster ◽  
N. A. J. Schutgens ◽  
J. W. Kaiser
Keyword(s):  
Black Carbon ◽  
Radiative Forcing ◽  
General Circulation ◽  
Circulation Model ◽  
Atmospheric Radiation ◽  
Orthogonal Polarization ◽  
Plume Height ◽  
Near Surface ◽  
The Impact ◽  
Emission Height

Abstract. Wildfires represent a major source for aerosols impacting atmospheric radiation, atmospheric chemistry and cloud micro-physical properties. Previous case studies indicated that the height of the aerosol–radiation interaction may crucially affect atmospheric radiation, but the sensitivity to emission heights has been examined with only a few models and is still uncertain. In this study we use the general circulation model ECHAM6 extended by the aerosol module HAM2 to investigate the impact of wildfire emission heights on atmospheric long-range transport, black carbon (BC) concentrations and atmospheric radiation. We simulate the wildfire aerosol release using either various versions of a semi-empirical plume height parametrization or prescribed standard emission heights in ECHAM6-HAM2. Extreme scenarios of near-surface or free-tropospheric-only injections provide lower and upper constraints on the emission height climate impact. We find relative changes in mean global atmospheric BC burden of up to 7.9±4.4 % caused by average changes in emission heights of 1.5–3.5 km. Regionally, changes in BC burden exceed 30–40 % in the major biomass burning regions. The model evaluation of aerosol optical thickness (AOT) against Moderate Resolution Imaging Spectroradiometer (MODIS), AErosol RObotic NETwork (AERONET) and Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) observations indicates that the implementation of a plume height parametrization slightly reduces the ECHAM6-HAM2 biases regionally, but on the global scale these improvements in model performance are small. For prescribed emission release at the surface, wildfire emissions entail a total sky top-of-atmosphere (TOA) radiative forcing (RF) of −0.16±0.06 W m−2. The application of a plume height parametrization which agrees reasonably well with observations introduces a slightly stronger negative TOA RF of −0.20±0.07 W m−2. The standard ECHAM6-HAM2 model in which 25 % of the wildfire emissions are injected into the free troposphere (FT) and 75 % into the planetary boundary layer (PBL), leads to a TOA RF of −0.24±0.06 W m−2. Overall, we conclude that simple plume height parametrizations provide sufficient representations of emission heights for global climate modeling. Significant improvements in aerosol wildfire modeling likely depend on better emission inventories and aerosol process modeling rather than on improved emission height parametrizations.

scholarly journals Correlation of black carbon aerosol and carbon monoxide in the high-altitude environment of Mt. Huang in Eastern China

2011 ◽  
Vol 11 (18) ◽  
pp. 9735-9747 ◽  
Author(s):  
X. L. Pan ◽  
Y. Kanaya ◽  
Z. F. Wang ◽  
Y. Liu ◽  
P. Pochanart ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
High Altitude ◽  
Black Carbon ◽  
Mass Concentration ◽  
Eastern China ◽  
Chemical Compositions ◽  
Strong Positive Correlation ◽  
Mixing Ratio ◽  
Air Masses ◽  
The Impact

Abstract. Understanding the relationship between black carbon (BC) and carbon monoxide (CO) will help improve BC emission inventories and the evaluation of global/regional climate forcing effects. In the present work, the BC (PM1) mass concentration and CO mixing ratio were continuously measured at a high-altitude background station on the summit of Mt. Huang (30.16° N, 118.26° E, 1840 m a.s.l.). Annual mean BC mass concentration was 1004.5 ± 895.5 ng m−3 with maxima in spring and autumn, and annual mean CO mixing ratio was 424.1 ± 159.2 ppbv. A large increase of CO was observed in the cold season, implying the contribution from the large-scale domestic coal/biofuel combustion for heating. The BC-CO relationship was found to show different seasonal features but strong positive correlation (R>0.8). In Mt. Huang area, the ΔBC/ΔCO ratio showed unimodal diurnal variations and had a maximum during the day (09:00–17:00 LST) and minimum at night (21:00–04:00 LST) in all seasons, indicating the impact of planetary boundary layer and the intrusion of clean air masses from the high troposphere. Back trajectory cluster analysis showed that the ΔBC/ΔCO ratio of plumes from the Eastern China (Jiangsu, Zhejiang provinces and Shanghai) was 8.8 ± 0.9 ng m−3 ppbv−1. Transportation and industry were deemed as controlling factors of the BC-CO relationship in this region. The ΔBC/ΔCO ratios for air masses from Northern China (Anhui, Henan, Shanxi and Shandong provinces) and southern China (Jiangxi, Fujian and Hunan provinces) were quite similar with mean values of 6.5 ± 0.4 and 6.5 ± 0.2 ng m−3 ppbv−1 respectively. The case studies combined with satellite observations demonstrated that the ΔBC/ΔCO ratio for biomass burning (BB) plumes were 10.3 ± 0.3 and 11.6 ± 0.5ng m−3 ppbv−1, significantly higher than those during non-BB impacted periods. The loss of BC during transport was also investigated on the basis of the ΔBC/ΔCO-RH (relative humidity) relationship along air mass pathways. The results showed that BC particles from Eastern China area was much more easily removed from atmosphere than other inland regions due to the higher RH along transport pathway, implying the importance of chemical compositions and mixing states on BC residence time in the atmosphere.

scholarly journals Aerosol optical characteristics and their vertical distributions under enhanced haze pollution events: effect of the regional transport of different aerosol types over eastern China

2017 ◽  
Author(s):  
Tianze Sun ◽  
Huizheng Che ◽  
Bing Qi ◽  
Yaqiang Wang ◽  
Yunsheng Dong ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Condition ◽  
Dust Particles ◽  
Hygroscopic Growth ◽  
Emission Layer ◽  
Regional Transport ◽  
Haze Pollution ◽  
Fine Mode ◽  
The Yrd ◽  
Pollution Events

Abstract. The climatological variation of aerosol properties and the planetary boundary layer (PBL) during 2013–2015 over the Yangtze River Delta (YRD) region were investigated by employing ground-based Microwave Pulse Lidar (MPL) and CE-318 sun-photometer observations. Combining MODIS and CALIPSO satellite products, enhanced haze pollution events affected by different types of aerosol over the YRD region were analyzed through vertical structures, spatial distributions, backward trajectories, and the Potential Source Contribution Function (PSCF) model. The results show that aerosols in the YRD are dominated by fine-mode particles, except in March. The aerosol optical depth (AOD) in June and September is higher due to high single scattering albedo (SSA) from hygroscopic growth, but is lower in July and August due to wet deposition from precipitation. The PBL height (PBLH) is greater (means ranging from 1.23 to 1.84 km) and more variable in the warmer months of March to August, due to the stronger diurnal cycle and exchange of heat. Northern fine-mode pollutants are brought to the YRD at a height of 1.5 km. The SSA increases blocking the radiation to the surface, and cooling the surface, thereby weakening turbulence, lowering the PBL, and in turn accelerating the accumulation of pollutants, creating a feedback to the cooling effect. Originated from the deserts in Xinjiang and Inner Mongolia, long-range transported dust masses are seen at heights of about 2 km over the YRD region with an SSA440 nm below 0.84, which heat air and upraise PBL, accelerating the diffusion of dust particles. Regional transport from biomass burning spots to the south of the YRD region bring mixed aerosol particles at a height below 1.5 km, resulting in an SSA440 nm below 0.89. During the winter, the accumulation of local emission layer is facilitated by stable weather condition, staying within the PBL even below 0.5 km.

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