<title>Absorption and scattering coefficient estimation with asymptotic apparent optical properties</title>

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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Tropospheric aerosol scattering and absorption over Central Europe: a closure study for the dry particle state

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-13-27811-2013 ◽

2013 ◽

Vol 13 (10) ◽

pp. 27811-27854 ◽

Cited By ~ 1

Author(s):

N. Ma ◽

W. Birmili ◽

T. Müller ◽

T. Tuch ◽

Y. F. Cheng ◽

...

Keyword(s):

Optical Properties ◽

Direct Measurement ◽

Radiative Forcing ◽

Control Measure ◽

Atmospheric Stability ◽

Scattering Coefficient ◽

Particle State ◽

Air Mass ◽

Aerosol Scattering ◽

Tropospheric Aerosol

Abstract. This work analyses optical properties of the dry tropospheric aerosol measured at the regional GAW observation site Melpitz in East Germany. For a continuous observation period between 2007 and 2010, we provide representative values of the dry-state scattering coefficient, the hemispheric backscattering coefficient, the absorption coefficient, single scattering albedo, and the Ångström exponent. Besides the direct measurement, the aerosol scattering coefficient was alternatively computed from experimental particle number size distributions using a Mie code. Within pre-defined limits, a closure could be achieved with the direct measurement. The achievement of closure implies that such calculations can be used as a high-level quality control measure for data sets involving multiple instrumentation. All dry optical properties showed significant annual variations, which were attributed to corresponding variations in the regional emission fluxes, the intensity of secondary particle formation, and the mixed layer height. Air mass classification showed that atmospheric stability is a major factor influencing the dry aerosol properties at the GAW station. In the cold season, temperature inversions limit the volume available for atmospheric mixing, so that the aerosol optical properties near the ground proved quite sensitive to the geographical origin of the air mass. In the warm season, when the atmosphere is usually well-mixed during day-time, considerably less variability was observed for the optical properties between different air masses. This work provides, on the basis of quality-checked in-situ measurements, a first step towards a climatological assessment of direct aerosol radiative forcing in the region under study.

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Relating hygroscopicity and optical properties to chemical composition and structure of secondary organic aerosol particles generated from the ozonolysis of α-pinene

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-14-10543-2014 ◽

2014 ◽

Vol 14 (7) ◽

pp. 10543-10596 ◽

Cited By ~ 5

Author(s):

C. Denjean ◽

P. Formenti ◽

B. Picquet-Varrault ◽

E. Pangui ◽

P. Zapf ◽

...

Keyword(s):

Optical Properties ◽

Secondary Organic Aerosol ◽

Complex Refractive Index ◽

Glassy State ◽

Particle Surface ◽

Chemical Properties ◽

Organic Aerosol ◽

Atomic Ratio ◽

Scattering Coefficient ◽

Size Growth

Abstract. Secondary Organic Aerosol (SOA) were generated from the ozonolysis of α-pinene in the CESAM simulation chamber. The formation and ageing of the SOA were studied by following their optical, hygroscopic and chemical properties. The optical properties investigated by determining the particle Complex Refractive Index (CRI). The hygroscopicity was quantified by measuring the effect of RH on particle size (Growth Factor, GF) and scattering coefficient (f(RH)). The oxygen to carbon (O : C) atomic ratio of the particle surface and bulk were used as a sensitive parameter to correlate the changes in hygroscopic and optical properties of the SOA composition in CESAM. The real CRI at 525 nm wavelength decreased from 1.43–1.60 (±0.02) to 1.32–1.38 (±0.02) during the SOA formation. The decrease in real CRI correlates with a decrease in the O : C ratio of SOA from 0.68 (±0.20) to 0.55 (±0.16). In contrast, the GF stayed roughly constant over the reaction time, with values of 1.02–1.07 (±0.02) at 90% (±4.2) RH. Simultaneous measurements of O : C ratio of the particle surface revealed that the SOA was not composed of a homogeneous mixture, but with less oxidised species at the surface which would limit the water adsorption onto particle. In addition, an apparent change of both mobility diameter and scattering coefficient with increasing RH from 0 to 30% was observed for SOA after 16 h reaction. We postulate that this change could be due to a change in the viscosity of the SOA from a predominantly glassy state to a predominantly liquid state.

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Optical Properties of the Urban Aerosol Particles Obtained from Ground Based Measurements and Satellite-Based Modelling Studies

Advances in Meteorology ◽

10.1155/2015/898376 ◽

2015 ◽

Vol 2015 ◽

pp. 1-12 ◽

Cited By ~ 1

Author(s):

Genrik Mordas ◽

Nina Prokopciuk ◽

Steigvilė Byčenkienė ◽

Jelena Andriejauskienė ◽

Vidmantas Ulevicius

Keyword(s):

Optical Properties ◽

Light Scattering ◽

Urban Environment ◽

Size Distribution ◽

Number Concentration ◽

Scattering Coefficient ◽

Dust Particles ◽

Aerosol Size Distribution ◽

Air Masses ◽

The Impact

Applications of satellite remote sensing data combined with ground measurements and model simulation were applied to study aerosol optical properties as well as aerosol long-range transport under the impact of large scale circulation in the urban environment in Lithuania (Vilnius). Measurements included the light scattering coefficients at 3 wavelengths (450, 550, and 700 nm) measured with an integrating nephelometer and aerosol particle size distribution (0.5–12 μm) and number concentration (Dpa> 0.5 μm) registered by aerodynamic particle sizer. Particle number concentration and mean light scattering coefficient varied from relatively low values of 6.0 cm−3and 12.8 Mm−1associated with air masses passed over Atlantic Ocean to relatively high value of 119 cm−3and 276 Mm−1associated with South-Western air masses. Analysis shows such increase in the aerosol light scattering coefficient (276 Mm−1) during the 3rd of July 2012 was attributed to a major Sahara dust storm. Aerosol size distribution with pronounced coarse particles dominance was attributed to the presence of dust particles, while resuspended dust within the urban environment was not observed.

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Influence of diffuse reflectance measurement accuracy on the scattering coefficient in determination of optical properties with integrating sphere optics (a secondary publication)

LASER THERAPY ◽

10.5978/islsm.15-or-19 ◽

2015 ◽

Vol 24 (4) ◽

pp. 303-310 ◽

Cited By ~ 3

Author(s):

Takuro Horibe ◽

Katsunori Ishii ◽

Daichi Fukutomi ◽

Kunio Awazu

Keyword(s):

Optical Properties ◽

Diffuse Reflectance ◽

Measurement Accuracy ◽

Scattering Coefficient ◽

Integrating Sphere ◽

Reflectance Measurement

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Global variability of aerosol optical properties retrieved from the network of GAW near-surface observatories

10.5194/egusphere-egu2020-3568 ◽

2020 ◽

Author(s):

Alessandro Bigi ◽

Martine Collaud Coen ◽

Elisabeth J. Andrews ◽

Clémence Rose ◽

Cathrine Lund Myhre ◽

...

Keyword(s):

Optical Properties ◽

Single Scattering ◽

Single Scattering Albedo ◽

Scattering Coefficient ◽

Near Surface ◽

World Data ◽

Data Centre ◽

The Impact ◽

Urban Sites ◽

Aerosol Properties

Atmospheric aerosols are known to play a key role in Earth&#8217;s radiative budget, although the quantification of their climate forcing is still highly uncertain. In order to improve the scientific understanding of their climatic effect, in-situ ground-based aerosol properties observations are needed by the research community. Such data would also allow the global assessment of the effect of environmental policies over both the short and the long term.To develop a robust and consistent view over time of the worldwide variability of aerosol properties, data resulting from a fully-characterized value chain, including uncertainty estimation, is needed.The present work is part of a wider project, having among its goals the investigation of the variability of climate-relevant aerosol properties observed at all sites connected to the Global Atmospheric Watch network, whose data are publicly available from the World Data Centre for Aerosols and follow the aforementioned specifications.This work focuses on aerosol optical proprieties, i.e. the aerosol light scattering coefficient (&#963;sp), the aerosol light absorption coefficient (&#963;ap), single scattering albedo (&#969;o) and both scattering and absorption &#197;ngstr&#246;m exponents (&#229;sp and &#229;ap).The analysis includes 108 yearly datasets collected either during 2016 or 2017 at different sites: 53 for absorption and 55 for scattering coefficient datasets, respectively. For 29 of these sites it was also possible to compute single scattering albedo.The spatial variability in extensive and intensive optical properties was analysed in terms of each site&#8217;s geographical location (either polar, continental, coastal or mountain) and its footprint (from pristine to urban, representing increasing levels of anthropogenic influence).The results highlight the impact of anthropogenic emissions and biomass burning on absolute levels and annual variability. The effect of sea spray or long range transport of dust is also evident for several sites, along with the influence of regional emissions. The largest seasonality in aerosol loading was observed at mountain sites under mixed footprint conditions, while the lowest seasonality occurred at urban sites. Urban sites also exhibited the highest &#963;sp and &#963;ap values. The lowest levels in &#963;sp and &#963;ap were observed at some polar sites, along with few coastal and mountain sites, despite their typically mixed footprint.AcknowledgementsThe authors acknowledge WMO-GAW World Data Centre on Aerosol for providing data available at http://ebas.nilu.no

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Aerosol optical properties in the North China Plain during HaChi campaign: an in-situ optical closure study

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-5959-2011 ◽

2011 ◽

Vol 11 (12) ◽

pp. 5959-5973 ◽

Cited By ~ 106

Author(s):

N. Ma ◽

C. S. Zhao ◽

A. Nowak ◽

T. Müller ◽

S. Pfeifer ◽

...

Keyword(s):

Optical Properties ◽

North China Plain ◽

North China ◽

Scattering Coefficient ◽

Aerosol Optical Properties ◽

Mean Values ◽

The North ◽

The North China Plain ◽

The Mean

Abstract. The largest uncertainty in the estimation of climate forcing stems from atmospheric aerosols. In early spring and summer of 2009, two periods of in-situ measurements on aerosol physical and chemical properties were conducted within the HaChi (Haze in China) project at Wuqing, a town between Beijing and Tianjin in the North China Plain (NCP). Aerosol optical properties, including the scattering coefficient (σsp), the hemispheric back scattering coefficient (σbsp), the absorption coefficient (σap), as well as the single scattering albedo (ω), are presented. The diurnal and seasonal variations are analyzed together with meteorology and satellite data. The mean values of σsp, 550 nm of the dry aerosol in spring and summer are 280±253 and 379±251 Mm−1, respectively. The average σap for the two periods is respectively 47±38 and 43±27 Mm−1. The mean values of ω at the wavelength of 637 nm are 0.82±0.05 and 0.86±0.05 for spring and summer, respectively. The relative high levels of σsp and σbsp are representative of the regional aerosol pollution in the NCP. Pronounced diurnal cycle of $σsp, σap and ω are found, mainly influenced by the evolution of boundary layer and the accumulation of local emissions during nighttime. The pollutants transported from the southwest of the NCP are more significant than that from the two megacities, Beijing and Tianjin, in both spring and summer. An optical closure experiment is conducted to better understand the uncertainties of the measurements. Good correlations (R>0.98) are found between the values measured by the nephelometer and the values calculated with a modified Mie model. The Monte Carlo simulation shows an uncertainty of about 30 % for the calculations. Considering all possible uncertainties of measurements, calculated σsp and σbsp agree well with the measured values, indicating a stable performance of instruments and thus reliable aerosol optical data.

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Optically Dilute, Absorbing, and Turbid Phantoms for Fluorescence Spectroscopy of Homogeneous and Inhomogeneous Samples

Applied Spectroscopy ◽

10.1366/0003702934066244 ◽

1993 ◽

Vol 47 (12) ◽

pp. 2114-2121 ◽

Cited By ~ 43

Author(s):

A. J. Durkin ◽

S. Jaikumar ◽

R. Richards-Kortum

Keyword(s):

Optical Properties ◽

Fluorescence Spectra ◽

Flavin Adenine Dinucleotide ◽

Emission Spectra ◽

Hemoglobin Concentration ◽

Scattering Coefficient ◽

Polystyrene Microspheres ◽

Fluorescence Excitation ◽

Structure Boundary ◽

Optical Properties Of Tissue

This paper presents a phantom which simulates the optical properties of tissue. The phantom absorption coefficient, scattering coefficient, anisotropy factor, and fluorescence quantum yield can be independently varied to investigate the effects of these parameters on fluorescence excitation and emission spectra from 300 to 650 nm. Phantom fluorophores include Flavin Adenine Dinucleotide (FAD) and Rhodamine B. Absorption is controlled by adjusting phantom hemoglobin concentration. On the basis of their smoothly varying scattering coefficient and the relatively low amount of fluorescence contributed to the mixture in comparison to other available scatterers, 1.05-µm-diameter polystyrene microspheres were selected as a scatterer. Sample inhomogeneities are simulated by preparing the phantom in a gelatin substrate. The optical properties of turbid phantoms determined with the use of indirect techniques agree well with known values as long as µs(l – g) > µa. Data are presented from dilute, absorbing, and turbid phantoms and inhomogeneous phantoms to qualitatively illustrate the effects of optical properties and sample geometry on fluorescence spectra. The phantom provides the framework for detailed quantitative investigations of the effects of optical properties, sample size, shape, and structure, boundary conditions, and collection geometry on fluorescence spectra.

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