Optical properties of atmospheric fine particles near Beijing during the HOPE-J&lt;sup&gt;3&lt;/sup&gt;A Campaign

Abstract. The optical properties and chemical composition of PM1.0 (particulate with an aerodynamic diameter of less than 1.0 μm) particles in a suburban environment (Huairou) near the mega-city Beijing were measured during the HOPE-J3A (Haze Observation Project Especially for Jing-Jin-Ji Area) field campaign. The campaign covered the period November 2014 to January 2015 during the winter coal heating season. The average and standard deviations for the extinction, scattering, absorption coefficients, and the aerosol single scattering albedo (SSA) at λ = 470 nm during the measurement period were 201 ± 240, 164 ± 202, 37 ± 43 Mm-1, and 0.80 ± 0.08, respectively. The mean mass scattering (MSE) and absorption (MAE) efficiencies were 4.77 ± 0.01 and 0.87 ± 0.03 m2g-1, respectively. Highly time-resolved air pollution episodes clearly show the dramatic evolution of the PM1.0 size distribution, extensive optical properties (extinction, scattering, and absorption coefficients) and intensive optical properties (single scattering albedo and complex refractive index) during haze formation, development and decline. Time periods were classified into three different pollution levels (clear, slightly polluted, and polluted) for further analysis. It was found that: (1) The diurnal patterns of the aerosol extinction, scattering, absorption coefficients, and SSA differed for the three pollution classes. (2) The real and imaginary part of complex refractive index (CRI) increased, while the SSA decreased from clear to polluted days. (3) The relative contributions of organic and inorganic species to observed aerosol composition changed significantly from clear to polluted days: the organic mass fraction decreased (50 to 43 %) while the proportion of sulfates, nitrates, and ammonium increased strongly (34 to 44 %). (4) The fractional contribution of chemical components to extinction coefficients was calculated by using the modified IMPROVE algorithm. Organic mass was the largest contributor (58 %) to the total extinction of PM1.0. When the air quality deteriorated, the change of the relative contribution of sulfate aerosol to the total extinction was small, but the contribution of nitrate aerosol increased significantly (from 17 % on clear days to 23 % on polluted days). (5) The observed mass scattering efficiencies increased consistently with the pollution extent, however, the observed mass absorption efficiencies increased consistently with increasing mass concentration in slightly pollution conditions, but decreased under polluted conditions.

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Optical properties of atmospheric fine particles near Beijing during the HOPE-J<sup>3</sup>A campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-6421-2016 ◽

2016 ◽

Vol 16 (10) ◽

pp. 6421-6439 ◽

Cited By ~ 22

Author(s):

Xuezhe Xu ◽

Weixiong Zhao ◽

Qilei Zhang ◽

Shuo Wang ◽

Bo Fang ◽

...

Keyword(s):

Optical Properties ◽

Fine Particles ◽

Complex Refractive Index ◽

Single Scattering ◽

Organic Mass ◽

Absorption Coefficients ◽

Aerosol Composition ◽

Average Mass ◽

Enhanced Absorption ◽

Inorganic Species

Abstract. The optical properties and chemical composition of PM1.0 particles in a suburban environment (Huairou) near the megacity of Beijing were measured during the HOPE-J3A (Haze Observation Project Especially for Jing–Jin–Ji Area) field campaign. The campaign covered the period November 2014 to January 2015 during the winter coal heating season. The average values and standard deviations of the extinction, scattering, absorption coefficients, and the aerosol single scattering albedo (SSA) at λ  =  470 nm during the measurement period were 201 ± 240, 164 ± 202, 37 ± 43 Mm−1, and 0.80 ± 0.08, respectively. The average values for the real and imaginary components of the effective complex refractive index (CRI) over the campaign were 1.40 ± 0.06 and 0.03 ± 0.02, while the average mass scattering and absorption efficiencies (MSEs and MAEs) of PM1.0 were 3.6 and 0.7 m2 g−1, respectively. Highly time-resolved air pollution episodes clearly show the dramatic evolution of the PM1.0 size distribution, extensive optical properties (extinction, scattering, and absorption coefficients), and intensive optical properties (SSA and CRI) during haze formation, development, and decline. Time periods were classified into three different pollution levels (clear, slightly polluted, and polluted) for further analysis. It was found that (1) the relative contributions of organic and inorganic species to observed aerosol composition changed significantly from clear to polluted days: the organic mass fraction decreased from 50 to 43 % while the proportion of sulfates, nitrates, and ammonium increased strongly from 34 to 44 %. (2) Chemical apportionment of extinction, calculated using the IMPROVE algorithm, tended to underestimate the extinction compared to measurements. Agreement with measurements was improved by modifying the parameters to account for enhanced absorption by elemental carbon (EC). Organic mass was the largest contributor (52 %) to the total extinction of PM1.0, while EC, despite its low mass concentration of ∼  4 %, contributed about 17 % to extinction. When the air quality deteriorated, the contribution of nitrate aerosol increased significantly (from 15 % on clear days to 22 % on polluted days). (3) Under polluted conditions, the average MAEs of EC were up to 4 times as large as the reference MAE value for freshly generated black carbon (BC). The temporal pattern of MAE values was similar to that of the OC / EC ratio, suggesting that non-BC absorption from secondary organic aerosol also contributes to particle absorption.

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Seasonal cycle and source analyses of aerosol optical properties in a semi-urban environment at Puijo station in Eastern Finland

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-5647-2012 ◽

2012 ◽

Vol 12 (12) ◽

pp. 5647-5659 ◽

Cited By ~ 16

Author(s):

A. Leskinen ◽

A. Arola ◽

M. Komppula ◽

H. Portin ◽

P. Tiitta ◽

...

Keyword(s):

Optical Properties ◽

Paper Mill ◽

Single Scattering ◽

Single Scattering Albedo ◽

Scattering Coefficient ◽

Traffic Density ◽

Aerosol Optical Properties ◽

Absorption Coefficients ◽

Data Set ◽

Pollutant Sources

Abstract. We introduce a four-year (in 2006–2010) continuous data set of aerosol optical properties at Puijo in Kuopio, Finland. We study the annual and diurnal variation of the aerosol scattering and absorption coefficients, hemispheric backscattering fraction, scattering Ångström exponent, and single scattering albedo, whose median values over this period were 7.2 Mm−1 (at 550 nm), 1.0 Mm−1 (at 637 nm), 0.15, 1.93 (between 450 and 550 nm), and 0.85, respectively. The scattering coefficient peaked in the spring and autumn, being 2–4 times those in the summer and winter. An exception was the summer of 2010, when the scattering coefficient was elevated to ~300 Mm−1 by plumes from forest fires in Russia. The absorption coefficient peaked in the winter when soot-containing particles derived from biomass burning were present. The higher relative absorption coefficients resulted in lower single scattering albedo in winter. The optical properties varied also with wind direction and time of the day, indicating the effect of the local pollutant sources and the age of the particles. Peak values in the single scattering albedo were observed when the wind blew from a paper mill and from the sector without local pollutant sources. These observations were linked, respectively, to the sulphate-rich aerosol from the paper mill and the oxygenated organics in the aged aerosol, which both are known to increase the scattering characteristics of aerosols. Decreases in the single scattering albedo in the morning and afternoon, distinct in the summertime, were linked to the increased traffic density at these hours. The scattering and absorption coefficients of residential and long-range transported aerosol (two separate cloud events) were found to be decreased by clouds. The effect was stronger for the scattering than absorption, indicating preferential activation of the more hygroscopic aerosol with higher scattering characteristics.

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Inter-comparison between the Aerosol Optical Properties Retrieved by Different Inversion Methods from SKYNET Sky Radiometer Observations over Qionghai and Yucheng in China

10.5194/amt-2019-39 ◽

2019 ◽

Author(s):

Zhe Jiang ◽

Minzheng Duan ◽

Huizheng Che ◽

Wenxing Zhang ◽

Teruyuki Nakajima ◽

...

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Complex Refractive Index ◽

Single Scattering ◽

Inversion Method ◽

Aerosol Optical Properties ◽

Validation Data ◽

Mean Values ◽

And Inversion ◽

Volume Size

Abstract. This study analyzed the aerosol optical properties derived by SKYRAD.pack versions 5.0 and 4.2 using the radiometer measurements over Qionghai and Yucheng in China, two new sites of the sky radiometer network (SKYNET). The volume size distribution retrieved by V5.0 presented bimodal patterns with a 0.1–0.2 μm fine particle mode and a 5–6 μm coarse particle mode both over Qionghai and Yucheng. The differences of the volume size distributions between the two versions were very large for the coarse mode with a radius of over 5 μm. The mean values of single scattering albedo (SSA) at 500 nm retrieved from V5.0 were approximately 0.02 lower, but 0.03 higher than those from V4.2 in Qionghai and Yucheng, respectively. The average imaginary part of the complex refractive index (mi) retrieved from V5.0 at all wavelengths was systemically higher than those by V4.2 over Qionghai. Moreover, the differences between the real parts of the complex refractive index (mr) obtained using the two versions were within 4.25 % both at Yucheng and Qionghai. The seasonal variability of the aerosol properties over Qionghai and Yucheng were investigated based on SKYRAD.pack V5.0. The seasonal average SSA during the winter was larger than those in other seasons in Yucheng, while the lowest SSA values occurred in winter over Qionghai. Meanwhile, the mr showed a minimum in winter over both sites. The results can provide validation data in China for SKYNET to continue improving the data-processing and inversion method. The results provide valuable references for continued improvement of the retrieval algorithms of SKYNET and other aerosol observational networks.

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Identifying Chemical Aerosol Signatures using Optical Suborbital Observations: How much can optical properties tell us about aerosol composition?

10.5194/acp-2021-761 ◽

2021 ◽

Author(s):

Meloë S. F. Kacenelenbogen ◽

Qian Tan ◽

Sharon P. Burton ◽

Otto P. Hasekamp ◽

Karl D. Froyd ◽

...

Keyword(s):

Remote Sensing ◽

Optical Properties ◽

Air Quality ◽

Chemical Transport ◽

Single Scattering ◽

Single Scattering Albedo ◽

Aerosol Optical Properties ◽

Aerosol Composition ◽

Ångström Exponent

Abstract. Improvements in air quality and Earth’s climate predictions require improvements of the aerosol speciation in chemical transport models, using observational constraints. Aerosol speciation (e.g., organic aerosols, black carbon, sulfate, nitrate, ammonium, dust or sea salt) is typically determined using in situ instrumentation. Continuous, routine surface network aerosol composition measurements are not uniformly widespread over the globe. Satellites, on the other hand, can provide a maximum coverage of the horizontal and vertical atmosphere but observe aerosol optical properties (and not aerosol speciation) based on remote sensing instrumentation. Combinations of satellite-derived aerosol optical properties can inform on air mass aerosol types (AMTs e.g., clean marine, dust, polluted continental). However, these AMTs are subjectively defined, might often be misclassified and are hard to relate to the critical parameters that need to be refined in models. In this paper, we derive AMTs that are more directly related to sources and hence to speciation. They are defined, characterized, and derived using simultaneous in situ gas-phase, chemical and optical instruments on the same aircraft during the Study of Emissions and Atmospheric Composition, Clouds, and Climate Coupling by Regional Surveys (SEAC4RS, US, summer of 2013). First, we prescribe well-informed AMTs that display distinct aerosol chemical and optical signatures to act as a training AMT dataset. These in situ observations reduce the errors and ambiguities in the selection of the AMT training dataset. We also investigate the relative skill of various combinations of aerosol optical properties to define AMTs and how much these optical properties can capture dominant aerosol speciation. We find distinct optical signatures for biomass burning (from agricultural or wildfires), biogenic and dust-influence AMTs. Useful aerosol optical properties to characterize these signatures are the extinction angstrom exponent (EAE), the single scattering albedo, the difference of single scattering albedo in two wavelengths, the absorption coefficient, the absorption angstrom exponent (AAE), and the real part of the refractive index (RRI). We find that all four AMTs studied when prescribed using mostly airborne in situ gas measurements, can be successfully extracted from at least three combinations of airborne in situ aerosol optical properties (e.g., EAE, AAE and RRI) over the US during SEAC4RS. However, we find that the optically based classifications for BB from agricultural fires and polluted dust include a large percentage of misclassifications that limit the usefulness of results relating to those classes. The technique and results presented in this study are suitable to develop a representative, robust and diverse source-based AMT database. This database could then be used for widespread retrievals of AMTs using existing and future remote sensing suborbital instruments/networks. Ultimately, it has the potential to provide a much broader observational aerosol data set to evaluate chemical transport and air quality models than is currently available by direct in situ measurements. This study illustrates how essential it is to explore existing airborne datasets to bridge chemical and optical signatures of different AMTs, before the implementation of future spaceborne missions (e.g., the next generation of Earth Observing System (EOS) satellites addressing Aerosol, Cloud, Convection and Precipitation (ACCP) designated observables).

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Vertical profiles of urban aerosol complex refractive index in the frame of ESQUIF airborne measurements

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-901-2008 ◽

2008 ◽

Vol 8 (4) ◽

pp. 901-919 ◽

Cited By ~ 35

Author(s):

J.-C. Raut ◽

P. Chazette

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Single Scattering ◽

In Situ Measurements ◽

Single Scattering Albedo ◽

Vertical Profiles ◽

Airborne Measurements ◽

Paris Area

Abstract. A synergy between lidar, sunphotometer and in situ measurements has been applied to airborne observations performed during the Etude et Simulation de la QUalité de l'air en Ile-de-France (ESQUIF), enabling the retrieval of vertical profiles for the aerosol complex refractive index (ACRI) and single-scattering albedo with a vertical resolution of 200 m over Paris area. The averaged value over the entire planetary boundary layer (PBL) for the ACRI is close to 1.51(±0.02)–i0.017(±0.003) at 532 nm. The single-scattering albedo of the corresponding aerosols is found to be ~0.9 at the same wavelength. A good agreement is found with previous studies for urban aerosols. A comparison of vertical profiles of ACRI with simulations combining in situ measurements and relative humidity (RH) profiles has highlighted a modification in aerosol optical properties linked to their history and the origin of the air mass. The determination of ACRI in the atmospheric column enabled to retrieve vertical profiles of extinction coefficient in accordance with lidar profiles measurements.

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Vertical profiles of urban aerosol complex refractive index in the frame of ESQUIF airborne measurements

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-10799-2007 ◽

2007 ◽

Vol 7 (4) ◽

pp. 10799-10835 ◽

Cited By ~ 2

Author(s):

J.-C. Raut ◽

P. Chazette

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Single Scattering ◽

In Situ Measurements ◽

Single Scattering Albedo ◽

Vertical Profiles ◽

Airborne Measurements ◽

Paris Area

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Intercomparison between aerosol optical properties by a PREDE skyradiometer and CIMEL sunphotometer over Beijing, China

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-3199-2008 ◽

2008 ◽

Vol 8 (12) ◽

pp. 3199-3214 ◽

Cited By ~ 73

Author(s):

H. Che ◽

G. Shi ◽

A. Uchiyama ◽

A. Yamazaki ◽

H. Chen ◽

...

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Complex Refractive Index ◽

Weather Conditions ◽

Single Scattering ◽

Single Scattering Albedo ◽

Aerosol Optical Properties ◽

Significant Difference ◽

Beijing China ◽

Volume Size

Abstract. This study compares the aerosol optical and physical properties simultaneously measured by a SKYNET PREDE skyradiometer and AERONET/PHOTONS CIMEL sunphotometer at a location in Beijing, China. Aerosol optical properties (AOP) including the Aerosol Optical Depth (AOD), Angstrom exponent (α), volume size distribution, single scattering albedo (ω) and the complex refractive index were compared. The difference between the two types of instruments was less than 1.3% for the AOD and less than 4% for the single scattering albedo below the wavelength of 670 nm. There is a difference between the volume size distribution patterns derived from two instruments, which is probably due to difference of measurement protocols and inversion algorithms for the respective instruments. AOP under three distinct weather conditions (background, haze, and dust days) over Beijing were compared by using the retrieved skyradiometer and sunphotometer data combined with MODIS satellite results, pyranometer measurements, PM10 measurements, and backtrajectory analysis. The results show that the significant difference of AOP under background, haze, and dust days over Beijing is probably due to different aerosol components under distinct weather conditions.

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Over a ten-year record of aerosol optical properties at SMEAR II

10.5194/acp-2018-981 ◽

2018 ◽

Author(s):

Krista Luoma ◽

Aki Virkkula ◽

Pasi Aalto ◽

Tuukka Petäjä ◽

Markku Kulmala

Keyword(s):

Optical Properties ◽

Volume Concentration ◽

Single Scattering ◽

Single Scattering Albedo ◽

Aerosol Optical Properties ◽

Absorption Coefficients ◽

Mean Values ◽

Aerosol Forcing ◽

Seasonal And Diurnal Variations ◽

The Mean

Abstract. The aerosol optical properties (AOPs) of particles smaller than 10 μm (PM10) and 1 μm (PM1) have been measured at SMEAR II since 2006 and 2010, respectively. For the PM10 particles the mean values of the scattering and absorption coefficients, single-scattering albedo, and backscatter fraction at δ = 550 nm, and scattering and absorption Ångström exponents at the wavelength ranges 450–700 nm and 370–950 nm were 15.2 Mm−1, 2.1 Mm−1, 0.86, 0.15, 1.80 and 0.94 respectively. The time series were used to examine the trends and variation in the AOPs. Statistically significant trends were found for example for the PM10 scattering and absorption coefficients, single-scattering albedo, and backscatter fraction, and the slopes of these trends were −0.342 Mm−1, −0.0952 Mm−1, 3.4 ‧ 10−3, and 1.3 ‧ 10−3 per year. The tendency for the extensive AOPs to decrease correlated well with the decrease in aerosol number and volume concentration. The tendency for the singlescattering albedo and backscattering fraction to increase affected to the effective aerosol forcing efficiency, indicating that the dry aerosols were scattering the radiation more effectively back into space. In addition to these trends, we also observed seasonal and diurnal variations and variations between the AOPs of the PM1 and PM10 particles.

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Over a 10-year record of aerosol optical properties at SMEAR II

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-11363-2019 ◽

2019 ◽

Vol 19 (17) ◽

pp. 11363-11382 ◽

Cited By ~ 2

Author(s):

Krista Luoma ◽

Aki Virkkula ◽

Pasi Aalto ◽

Tuukka Petäjä ◽

Markku Kulmala

Keyword(s):

Optical Properties ◽

Size Distribution ◽

Radiative Forcing ◽

Aerosol Particles ◽

Single Scattering ◽

Single Scattering Albedo ◽

Aerosol Size Distribution ◽

Forest Site ◽

Aerosol Optical Properties ◽

Absorption Coefficients

Abstract. Aerosol optical properties (AOPs) describe the ability of aerosols to scatter and absorb radiation at different wavelengths. Since aerosol particles interact with the sun's radiation, they impact the climate. Our study focuses on the long-term trends and seasonal variations of different AOPs measured at a rural boreal forest site in northern Europe. To explain the observed variations in the AOPs, we also analyzed changes in the aerosol size distribution. AOPs of particles smaller than 10 µm (PM10) and 1 µm (PM1) have been measured at SMEAR II, in southern Finland, since 2006 and 2010, respectively. For PM10 particles, the median values of the scattering and absorption coefficients, single-scattering albedo, and backscatter fraction at λ=550 nm were 9.8 Mm−1, 1.3 Mm−1, 0.88, and 0.14. The median values of scattering and absorption Ångström exponents at the wavelength ranges 450–700 and 370–950 nm were 1.88 and 0.99, respectively. We found statistically significant trends for the PM10 scattering and absorption coefficients, single-scattering albedo, and backscatter fraction, and the slopes of these trends were −0.32 Mm−1, −0.086 Mm−1, 2.2×10-3, and 1.3×10-3 per year. The tendency for the extensive AOPs to decrease correlated well with the decrease in aerosol number and volume concentrations. The tendency for the backscattering fraction and single-scattering albedo to increase indicates that the aerosol size distribution consists of fewer larger particles and that aerosols absorb less light than at the beginning of the measurements. The trends of the single-scattering albedo and backscattering fraction influenced the aerosol radiative forcing efficiency, indicating that the aerosol particles are scattering the radiation more effectively back into space.

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

Remote Sensing ◽

10.3390/rs10040518 ◽

2018 ◽

Vol 10 (4) ◽

pp. 518 ◽

Cited By ~ 8

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.

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