Spatial distribution and temporal variation of aerosol optical depth in the Sichuan basin, China, the recent ten years

Liu, Xinyu; Chen, Quanliang; Che, Huizheng; Zhang, Renjian; Gui, Ke; Zhang, Huan; Zhao, Tianliang

doi:10.1016/j.atmosenv.2016.10.008

Cited by 74 publications

(53 citation statements)

References 53 publications

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“…Although the correlation between AOD and PM 2.5 mass concentration depends on many factors, such as aerosol size distribution, refractive index, single-scattering albedo and meteorological factors Guo et al, 2009bGuo et al, , 2017, the predicted PM 2.5 mass from satellite AOD data compared well with ground-level measurements Xie et al, 2015b). Moreover, the spatial distributions of AOD measured using sun photometers mostly agreed with those retrieved from satellite data (Che et al, 2014Liu et al, 2016b;Pan et al, 2010). Spatial distributions of annual average AOD in 2014 are shown in Fig.…”

Section: Aerosol Optical Propertiessupporting

confidence: 60%

A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

et al. 2017

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Abstract. To obtain a thorough knowledge of PM 2.5 chemical composition and its impact on aerosol optical properties across China, existing field studies conducted after the year 2000 are reviewed and summarized in terms of geographical, interannual and seasonal distributions. Annual PM 2.5 was up to 6 times the National Ambient Air Quality Standards (NAAQS) in some megacities in northern China. Annual PM 2.5 was higher in northern than southern cities, and higher in inland than coastal cities. In a few cities with data longer than a decade, PM 2.5 showed a slight decrease only in the second half of the past decade, while carbonaceous aerosols decreased, sulfate (SO 2− 4 ) and ammonium (NH + 4 ) remained at high levels, and nitrate (NO − 3 ) increased. The highest seasonal averages of PM 2.5 and its major chemical components were typically observed in the cold seasons. Annual average contributions of secondary inorganic aerosols to PM 2.5 ranged from 25 to 48 %, and those of carbonaceous aerosols ranged from 23 to 47 %, both with higher contributions in southern regions due to the frequent dust events in northern China. Source apportionment analysis identified secondary inorganic aerosols, coal combustion and traffic emission as the top three source factors contributing to PM 2.5 mass in most Chinese cities, and the sum of these three source factors explained 44 to 82 % of PM 2.5 mass on annual average across China. Biomass emission in most cities, industrial emission in industrial cities, dust emission in northern cities and ship emission in coastal cities are other major source factors, each of which contributed 7-27 % to PM 2.5 mass in applicable cities.The geographical pattern of scattering coefficient (b sp ) was similar to that of PM 2.5 , and that of aerosol absorption coefficient (b ap ) was determined by elemental carbon (EC) mass concentration and its coating. b sp in ambient condition of relative humidity (RH) = 80 % can be amplified by about 1.8 times that under dry conditions. Secondary inorganic aerosols accounted for about 60 % of aerosol extinction coefficient (b ext ) at RH greater than 70 %. The mass scattering efficiency (MSE) of PM 2.5 ranged from 3.0 to 5.0 m 2 g −1 for aerosols produced from anthropogenic emissions and from 0.7 to 1.0 m 2 g −1 for natural dust aerosols. The mass absorption efficiency (MAE) of EC ranged from 6.5 to 12.4 m 2 g −1 in urban environments, but the MAE of water-soluble organic carbon was only 0.05 to 0.11 m 2 g −1 . Historical emission control policies in China and their effectiveness were discussed based on available chemically resolved PM 2.5 data, which provides the much needed knowledge for guiding future studies and emissions policies.

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Section: Aerosol Optical Propertiessupporting

confidence: 60%

A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

et al. 2017

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“…This implies an increase in the albedo of a cloud, resulting in enhanced reflection and a cooling effect (Twomey, 1977). Several studies using space-, surface-, and ship-based measurements have revealed the strong impact of aerosols on cloud droplet size, COD, and cloud reflection and emission (Feingold, 2003;Feingold et al, 2006;Kim et al, 2008;Liu, Chen, et al, 2016;Liu & Li, 2018a), indicating that the magnitude of the FIE differs drastically depending on aerosol properties, meteorological conditions, analysis methods, and so on (Liu & Li, 2018b;Liu, Chen, et al, 2016;Rosenfeld & Feingold, 2003;. Under highly polluted conditions over eastern China, a positive FIE was observed; that is, cloud droplet effective radii increased with AOD ( Huang et al, 2015;Wang, Guo, et al, 2015) and the aerosol swelling effect (Liu & Li, 2018b), or both.…”

Section: Impact Of Aerosols On Cloudsmentioning

confidence: 99%

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIR_CPC)

et al. 2019

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Aerosols have significant and complex impacts on regional climate in East Asia. Cloud‐aerosol‐precipitation interactions (CAPI) remain most challenging in climate studies. The quantitative understanding of CAPI requires good knowledge of aerosols, ranging from their formation, composition, transport, and their radiative, hygroscopic, and microphysical properties. A comprehensive review is presented here centered on the CAPI based chiefly, but not limited to, publications in the special section named EAST‐AIRcpc concerning (1) observations of aerosol loading and properties, (2) relationships between aerosols and meteorological variables affecting CAPI, (3) mechanisms behind CAPI, and (4) quantification of CAPI and their impact on climate. Heavy aerosol loading in East Asia has significant radiative effects by reducing surface radiation, increasing the air temperature, and lowering the boundary layer height. A key factor is aerosol absorption, which is particularly strong in central China. This absorption can have a wide range of impacts such as creating an imbalance of aerosol radiative forcing at the top and bottom of the atmosphere, leading to inconsistent retrievals of cloud variables from space‐borne and ground‐based instruments. Aerosol radiative forcing can delay or suppress the initiation and development of convective clouds whose microphysics can be further altered by the microphysical effect of aerosols. For the same cloud thickness, the likelihood of precipitation is influenced by aerosols: suppressing light rain and enhancing heavy rain, delaying but intensifying thunderstorms, and reducing the onset of isolated showers in most parts of China. Rainfall has become more inhomogeneous and more extreme in the heavily polluted urban regions.

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“…Based on two-year CALIOP aerosol profiles data, the existence of valid extinction coefficient values in higher atmospheric layer indicated that the elevated aerosol layer was inclined to appear in these two regions. Because the southwest is significantly influenced by air masses originating from western desert regions and northern desert regions due to the East Asian and Indian monsoons [62], while the northeast is more affected by air masses from the North China region travelling through intensive industrial areas with heavy pollution [63]. These extraneous aerosols lead to the occurrence of elevated aerosol layers in Central China; therefore, the AOD vertically corrected by CALIOP ratio is recommended for PM 2.5 estimation in northeastern and southwestern regions.…”

Section: The Recommended Vertical Correction Schemesmentioning

confidence: 99%

Impact and Suggestion of Column-to-Surface Vertical Correction Scheme on the Relationship between Satellite AOD and Ground-Level PM2.5 in China

et al. 2017

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As China is suffering from severe fine particle pollution from dense industrialization and urbanization, satellite-derived aerosol optical depth (AOD) has been widely used for estimating particulate matter with an aerodynamic diameter less than 2.5 µm (PM 2.5 ). However, the correlation between satellite AOD and ground-level PM 2.5 could be influenced by aerosol vertical distribution, as satellite AOD represents the entire column, rather than just ground-level concentration. Here, a new column-to-surface vertical correction scheme is proposed to improve separation of the near-surface and elevated aerosol layers, based on the ratio of the integrated extinction coefficient within 200-500 m above ground level (AGL), using the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)) aerosol profile products. There are distinct differences in climate, meteorology, terrain, and aerosol transmission throughout China, so comparisons between vertical correction via CALIOP ratio and planetary boundary layer height (PBLH) were conducted in different regions from 2014 to 2015, combined with the original Pearson coefficient between satellite AOD and ground-level PM 2.5 for reference. Furthermore, the best vertical correction scheme was suggested for different regions to achieve optimal correlation with PM 2.5 , based on the analysis and discussion of regional and seasonal characteristics of aerosol vertical distribution. According to our results and discussions, vertical correction via PBLH is recommended in northwestern China, where the PBLH varies dramatically, stretching or compressing the surface aerosol layer; vertical correction via the CALIOP ratio is recommended in northeastern China, southwestern China, Central China (excluding summer), North China Plain (excluding Beijing), and the spring in the southeast coast, areas that are susceptible to exogenous aerosols and exhibit the elevated aerosol layer; and original AOD without vertical correction is recommended in Beijing and the southeast coast (excluding spring), where the elevated aerosol layer rarely occurs and a large proportion of aerosol is aggregated in near-surface. Moreover, validation experiments in 2016 agreed well with our discussions and conclusions drawn from the experiments of the first two years. Furthermore, suggested vertical correction scheme was applied into linear mixed effect (LME) model, and high cross validation (CV) R 2 (~85%) and relatively low root mean square errors (RMSE,~20 µg/m 3 ) were achieved, which demonstrated that the PM 2.5 estimation agreed well with the measurements. When compared to the original situation, CV R 2 values and RMSE after vertical correction both presented improvement to a certain extent, proving that the suggested vertical correction schemes could further improve the estimation accuracy of PM 2.5 based on sophisticated model in China. Estimating PM 2.5 with better accuracy could contribute to a more

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Spatial distribution and temporal variation of aerosol optical depth in the Sichuan basin, China, the recent ten years

Cited by 74 publications

References 53 publications

A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIR_CPC)

Impact and Suggestion of Column-to-Surface Vertical Correction Scheme on the Relationship between Satellite AOD and Ground-Level PM2.5 in China

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Spatial distribution and temporal variation of aerosol optical depth in the Sichuan basin, China, the recent ten years

Cited by 74 publications

References 53 publications

A review of current knowledge concerning PM&lt;sub&gt;2. 5&lt;/sub&gt; chemical composition, aerosol optical properties and their relationships across China

A review of current knowledge concerning PM&lt;sub&gt;2. 5&lt;/sub&gt; chemical composition, aerosol optical properties and their relationships across China

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIRCPC)

Impact and Suggestion of Column-to-Surface Vertical Correction Scheme on the Relationship between Satellite AOD and Ground-Level PM2.5 in China

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A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

A review of current knowledge concerning PM<sub>2. 5</sub> chemical composition, aerosol optical properties and their relationships across China

East Asian Study of Tropospheric Aerosols and their Impact on Regional Clouds, Precipitation, and Climate (EAST‐AIR_CPC)