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.

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

2018 ◽  
Vol 18 (4) ◽  
pp. 2949-2971 ◽  
Author(s):  
Tianze Sun ◽  
Huizheng Che ◽  
Bing Qi ◽  
Yaqiang Wang ◽  
Yunsheng Dong ◽  
...  
Keyword(s):  
Eastern China ◽  
Weather Conditions ◽  
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 Micro Pulse Lidar (MPL) and CE-318 sun-photometer observations. Combining Moderate Resolution Imaging Spectroradiometer (MODIS) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (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 it 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 raise the 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 the local emission layer is facilitated by stable weather conditions, staying within the PBL even below 0.5 km.

scholarly journals Hygroscopicity of Different Types of Aerosol Particles: Case Studies Using Multi-Instrument Data in Megacity Beijing, China

2020 ◽  
Vol 12 (5) ◽  
pp. 785 ◽  
Author(s):  
Tong Wu ◽  
Zhanqing Li ◽  
Jun Chen ◽  
Yuying Wang ◽  
Hao Wu ◽  
...  
Keyword(s):  
Enhancement Factor ◽  
Mineral Dust ◽  
Aerosol Particles ◽  
Dust Aerosol ◽  
Dust Particles ◽  
Chemical Components ◽  
Hygroscopic Growth ◽  
Microphysical Properties ◽  
Fine Mode ◽  
Fine Mode Aerosol

Water uptake by aerosol particles alters its light-scattering characteristics significantly. However, the hygroscopicities of different aerosol particles are not the same due to their different chemical and physical properties. Such differences are explored by making use of extensive measurements concerning aerosol optical and microphysical properties made during a field experiment from December 2018 to March 2019 in Beijing. The aerosol hygroscopic growth was captured by the aerosol optical characteristics obtained from micropulse lidar, aerosol chemical composition, and aerosol particle size distribution information from ground monitoring, together with conventional meteorological measurements. Aerosol hygroscopicity behaves rather distinctly for mineral dust coarse-mode aerosol (Case I) and non-dust fine-mode aerosol (Case II) in terms of the hygroscopic enhancement factor, f β ( R H , λ 532 ) , calculated for the same humidity range. The two types of aerosols were identified by applying the polarization lidar photometer networking method (POLIPHON). The hygroscopicity for non-dust aerosol was much higher than that for dust conditions with the f β ( R H , λ 532 ) being around 1.4 and 3.1, respectively, at the relative humidity of 86% for the two cases identified in this study. To study the effect of dust particles on the hygroscopicity of the overall atmospheric aerosol, the two types of aerosols were identified and separated by applying the polarization lidar photometer networking method in Case I. The hygroscopic enhancement factor of separated non-dust fine-mode particles in Case I had been significantly strengthened, getting closer to that of the total aerosol in Case II. These results were verified by the hygroscopicity parameter, κ (Case I non-dust particles: 0.357 ± 0.024; Case II total: 0.344 ± 0.026), based on the chemical components obtained by an aerosol chemical speciation instrument, both of which showed strong hygroscopicity. It was found that non-dust fine-mode aerosol contributes more during hygroscopic growth and that non-hygroscopic mineral dust aerosol may reduce the total hygroscopicity per unit volume in Beijing.

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 Source, transport and impacts of a heavy dust event in the Yangtze River Delta, China in 2011

2013 ◽  
Vol 13 (8) ◽  
pp. 21507-21540
Author(s):  
X. Fu ◽  
S. X. Wang ◽  
Z. Cheng ◽  
J. Xing ◽  
B. Zhao ◽  
...  
Keyword(s):  
Air Quality ◽  
Yangtze River ◽  
Eastern China ◽  
Yangtze River Delta ◽  
River Delta ◽  
Dust Particles ◽  
The Yangtze River ◽  
Dust Event ◽  
The Yrd ◽  
The Yangtze River Delta

Abstract. During 1 to 6 May 2011, a dust event was observed in the Yangtze River Delta region (YRD). The highest PM10 concentration reached over 1000 μg m−3 and the visibility was below 3 km. In this study, the Community Multi-scale Air Quality modeling system (CMAQ5.0) coupled with an in-line windblown dust model was used to simulate the formation, spatial and temporal characteristics of this dust event, and analyze its impacts on deposition and photochemistry. The threshold friction velocity for loose smooth surface in the dust model was revised based on Chinese data to improve the model performance. The comparison between predictions and observations indicates the revised model can reproduce the transport and pollution of the event. The simulation results show that the dust event was affected by formation and transport of Mongolian cyclone and cold air. Totally about 695 kt dust particles (PM10) were emitted in Xinjiang Province and Mongolia during 28 to 30 April, the dust band swept northern, eastern China and then arrived in the YRD region on 1 May 2011. The transported dust particles increased the mean surface layer concentrations of PM10 in the YRD region by 372% during 1 to 6 May and the impacts weakened from north to south due to the removal of dust particles along the path. Accompanied by high PM concentration, the dry deposition, wet deposition and total deposition of PM10 in the YRD reached 184.7 kt, 172.6 kt and 357.32 kt, respectively. These deposited particles are very harmful because of their impacts on urban environment as well as air quality and human health when resuspending in the atmosphere. Due to the impacts of mineral dust on atmospheric photolysis, the concentrations of O3 and OH were reduced by 1.5% and 3.1% in the whole China, and by 9.4% and 12.1% in the YRD region, respectively. The work of this manuscript is meaningful for understanding the dust emissions in China as well as for the application of CMAQ in Asia. It is also helpful to understand the formation mechanism and impacts of dust pollution in the YRD.

scholarly journals Impacts of atmospheric circulations on aerosol distributions in autumn over eastern China: observational evidences

2015 ◽  
Vol 15 (3) ◽  
pp. 3285-3325 ◽  
Author(s):  
X.-Y. Zheng ◽  
Y.-F. Fu ◽  
Y.-J. Yang ◽  
G.-S. Liu
Keyword(s):  
Eastern China ◽  
Weather Condition ◽  
Reanalysis Data ◽  
East China ◽  
Economic Activities ◽  
Middle Troposphere ◽  
Atmospheric Circulations ◽  
Heavy Pollution ◽  
The Government ◽  
Pollution Events

Abstract. Regional heavy pollution events in East China (110–122° E, 28–40° N) are the main environmental problems recently because of the high urbanization and rapid economic development connected with too much emissions of pollutants. However, appropriate weather condition is another factor which cannot be ignored for these events. In this study, the relationship between regional pollution status and larger scale atmospheric circulations over East China in October is investigated using ten-year (2001–2010) MODIS/Terra aerosol optical depth (AOD) product and the NCEP reanalysis data together with case analysis and composite analysis. Generally, statistics in East China show values of mean AOD vary from 0.3 to 0.9 in October over the region, and larger AOD variances are accompanied with the distribution of higher average AOD. Eighteen pollution episodes (regional mean AOD > 0.6) and ten clean episodes (regional mean AOD < 0.4) are selected and then categorized into six polluted types and three clean types, respectively. Each type represents different weather pattern associated with the combination of lower and upper atmospheric circulation. Generally, the uniform surface pressure field in East China or steady straight westerly in middle troposphere, particularly the rear of anticyclone at 850 hPa, are typical weather patterns responsible for heavy pollution events, while clean episodes occur when strong southeastward cold air advection prevails below the middle troposphere or air masses are transported from sea to the mainland. The above studies are especially useful to the government decision make on balance of economic activities and pollution mitigations.

scholarly journals Haze Optical Properties from Long-Term Ground-Based Remote Sensing over Beijing and Xuzhou, China

2018 ◽  
Vol 10 (4) ◽  
pp. 518 ◽  
Author(s):  
Kai Qin ◽  
Luyao Wang ◽  
Jian Xu ◽  
Husi Letu ◽  
Kefei Zhang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Fine Particles ◽  
Global Climate ◽  
Complex Refractive Index ◽  
Eastern China ◽  
Single Scattering ◽  
Dust Particles ◽  
Haze Pollution

Aerosol haze pollution has had a significant impact on both global climate and the regional air quality of Eastern China, which has a high proportion of high level pollution days. Statistical analyses of aerosol optical properties and direct radiative forcing at two AERONET sites (Beijing and Xuzhou) were conducted from 2013 to 2016. Results indicate: (1) Haze pollution days accounted for 26% and 20% of days from 2013 to 2016 in Beijing and Xuzhou, respectively, with the highest proportions in winter; (2) The averaged aerosol optical depth (AOD) at 550 nm on haze days were about 3.7 and 1.6 times greater than those on clean days in Beijing and Xuzhou, respectively. At both sites, the maximum AOD occurred in summer; (3) Hazes were dominated by fine particles at both sites. However, as compared to Xuzhou, Beijing had larger coarse mode AOD and higher percentage of small α. This data, together with an analysis of size distribution, suggests that the hazes in Beijing were more susceptible to coarse dust particles than Xuzhou; (4) During hazes in Beijing, the single scattering albedo (SSA) is significantly higher when compared to clean conditions (0.874 vs. 0.843 in SSA440 nm), an increase much less evident in Xuzhou. The most noticeable differences in both SSA and the imaginary part of the complex refractive index between Beijing and Xuzhou were found in winter; (5) In Beijing, the haze radiative forcing produced an averaged cooling effect of −113.6 ± 63.7 W/m2 at the surface, whereas the averaged heating effect of 77.5 ± 49.7 W/m2 within the atmosphere was at least twice as strong as clean days. In Xuzhou, such a radiative forcing effect appeared to be much smaller and the difference between haze and clean days was insignificant. Derived from long-term observation, these findings are more significant for the improvement of our understanding of haze formation in China and the assessment of its impacts on radiative forcing of climate change than previous short-term case studies.

scholarly journals The optical properties, physical properties and direct radiative forcing of urban columnar aerosols in the Yangtze River Delta, China

2018 ◽  
Vol 18 (2) ◽  
pp. 1419-1436 ◽  
Author(s):  
Bingliang Zhuang ◽  
Tijian Wang ◽  
Jane Liu ◽  
Huizheng Che ◽  
Yong Han ◽  
...  
Keyword(s):  
Optical Properties ◽  
Physical Properties ◽  
Yangtze River ◽  
Eastern China ◽  
Yangtze River Delta ◽  
River Delta ◽  
Transfer Model ◽  
Size Distributions ◽  
Haze Pollution ◽  
The Yrd

Abstract. The optical and physical properties as well as the direct radiative forcings (DRFs) of fractionated aerosols in the urban area of the western Yangtze River Delta (YRD) are investigated with measurements from a Cimel sun photometer combined with a radiation transfer model. Ground-based observations of aerosols have much higher temporal resolutions than satellite retrievals. An initial analysis reveals the characteristics of the optical properties of different types of fractionated aerosols in the western YRD. The total aerosols, mostly composed of scattering components (93.8 %), have mean optical depths of 0.65 at 550 nm and refractive index of 1.44 + 0.0084i at 440 nm. The fine aerosols are approximately four times more abundant and have very different compositions from coarse aerosols. The absorbing components account for only  ∼  4.6 % of fine aerosols and 15.5 % of coarse aerosols and have smaller sizes than the scattering aerosols within the same mode. Therefore, fine particles have stronger scattering than coarse ones, simultaneously reflecting the different size distributions between the absorbing and scattering aerosols. The relationships among the optical properties quantify the aerosol mixing and imply that approximately 15 and 27.5 % of the total occurrences result in dust- and black-carbon-dominating mixing aerosols, respectively, in the western YRD. Unlike the optical properties, the size distributions of aerosols in the western YRD are similar to those found at other sites over eastern China on a climatological scale, peaking at radii of 0.148 and 2.94 µm. However, further analysis reveals that the coarse-dominated particles can also lead to severe haze pollution over the YRD. Observation-based estimations indicate that both fine and coarse aerosols in the western YRD exert negative DRFs, and this is especially true for fine aerosols (−11.17 W m−2 at the top of atmosphere, TOA). A higher absorption fraction leads directly to the negative DRF being further offset for coarse aerosols (−0.33 W m−2) at the TOA. Similarly, the coarse-mode DRF contributes to only 13.3 % of the total scattering aerosols but > 33.7 % to the total absorbing aerosols. A sensitivity analysis states that aerosol DRFs are not highly sensitive to their profiles in clear-sky conditions. Most of the aerosol properties and DRFs have substantial seasonality in the western YRD. The results further reveal the contributions of each component of the different size particles to the total aerosol optical depths (AODs) and DRFs. Additionally, these results can be used to improve aerosol modelling performance and the modelling of aerosol effects in the eastern regions of China.

scholarly journals The Influence of Climate Factors, Meteorological Conditions, and Boundary-Layer Structure on Severe Haze Pollution in the Beijing-Tianjin-Hebei Region during January 2013

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Lili Wang ◽  
Nan Zhang ◽  
Zirui Liu ◽  
Yang Sun ◽  
Dongsheng Ji ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Layer Structure ◽  
High Humidity ◽  
Surface Winds ◽  
Hygroscopic Growth ◽  
Boundary Layer Structure ◽  
Haze Pollution ◽  
Weak Surface ◽  
Pollution Events ◽  
Bth Region

The air-pollution episodes in China in January 2013 were the most hazardous in the Beijing-Tianjin-Hebei (BTH) region. PM2.5, AOD, and long-term visibility data, along with various climate and meteorological factors and the boundary-layer structure, were used to investigate the cause of the heavy-haze pollution events in January 2013. The result suggests that unfavorable diffusion conditions (weak surface winds and high humidity) and high primary-pollutant emissions have induced heavy-haze pollution in the BTH region over the past two decades. A sudden stratospheric warming (SSW), weak East Asian winter monsoon, a weak Siberian High, weak meridional circulation, southerly wind anomalies in the lower troposphere, and abnormally weak surface winds and high humidity were responsible for the severe haze pollution events, rather than an abrupt increase in emissions. Heavy/severe haze pollution is associated with orographic wind convergence zones along the Taihang and Yanshan Mountains, slight winds (1.7∼2.1 m/s), and high humidity (70%∼90%), which limits the diffusion of pollutants and facilitates the hygroscopic growth of aerosols. Recirculation and regional transport, along with the poorest diffusion conditions and favorable conditions for hygroscopic growth of aerosols and secondary transformation under the high emission, led to explosive growth and the record high hourly average concentration of PM2.5in Beijing.

Impact of air transport and secondary formation on haze pollution in the Yangtze River Delta: In situ online observations in Shanghai and Nanjing

2020 ◽  
Author(s):  
Peng Sun
Keyword(s):  
Fine Particles ◽  
Eastern China ◽  
Northern China ◽  
Organic Aerosol ◽  
Photochemical Activity ◽  
Air Transport ◽  
Ozone Level ◽  
Haze Pollution ◽  
The Yrd ◽  
Pollution Episodes

&lt;p&gt;Despite frequent haze pollution in China in recent years, our knowledge of regional pollution episodes associated with air transport and synoptic weather systems is limited. In this study, we conducted two intensive campaigns simultaneously to measure the highly time-resolved chemical composition of fine particles (PM&lt;sub&gt;2.5&lt;/sub&gt;) in suburban Shanghai and Nanjing during the winter of 2017 and the summer of 2018. The average PM&lt;sub&gt;2.5&lt;/sub&gt; mass concentrations were 53.9 (65.7) &amp;#181;g m&lt;sup&gt;-3&lt;/sup&gt; and 32.8 (37.3) &amp;#181;g m&lt;sup&gt;-3 &lt;/sup&gt;in Shanghai (Nanjing) in winter and summer, respectively. In winter, extreme haze episodes were observed synchronously with enhanced contributions of nitrate at both sites and of low-volatile oxidized organic aerosol (LV-OOA) in Shanghai. Long-range transport from Northern China was demonstrated to play an important role in the episodes, which occurred simultaneously at both sites. Influenced by the cold fronts, Nanjing had a relatively longer pollution duration, whereas Shanghai exhibited faster PM increases. In summer, air masses passing though the city-clusters of the YRD were responsible for the pollution episodes. Low wind speeds, which favored the accumulation of primary aerosols, and strong photochemical activity indicated by high ozone level, which promoted the formation of secondary aerosols, resulted in elevated contributions of nitrate, Hydrocarbon-like organic aerosol (HOA) and semi-volatile oxidized organic aerosol (SV-OOA) to PM in Shanghai. In addition, a pollution episode dominated by increases of nitrate and organic aerosols was observed in Nanjing two days later despite the clean situation in Shanghai. Our results highlight the importance of regional or sub-regional emission control to mitigate haze pollution in city clusters, such as the YRD in Eastern China.&lt;/p&gt;

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