scholarly journals Extinction-related Angström exponent characterization of submicrometric volume fraction in atmospheric aerosol particles

2019 ◽  
Vol 228 ◽  
pp. 270-280 ◽  
Author(s):  
A. Quirantes ◽  
J.L. Guerrero-Rascado ◽  
D. Pérez-Ramírez ◽  
I. Foyo-Moreno ◽  
P. Ortiz-Amezcua ◽  
...  
Keyword(s):  
Atmospheric Aerosol ◽  
Volume Fraction ◽  
Aerosol Particles ◽  
Angstrom Exponent ◽  
Atmospheric Aerosol Particles ◽  
Ångström Exponent ◽  
Ångstrom Exponent

scholarly journals Calibration of LACIS as a CCN detector and its use in measuring activation and hygroscopic growth of atmospheric aerosol particles

2006 ◽  
Vol 6 (12) ◽  
pp. 4519-4527 ◽  
Author(s):  
H. Wex ◽  
A. Kiselev ◽  
M. Ziese ◽  
F. Stratmann
Keyword(s):  
Sodium Chloride ◽  
Wall Temperature ◽  
Atmospheric Aerosol ◽  
Volume Fraction ◽  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Urban Aerosol ◽  
Hygroscopic Growth ◽  
Atmospheric Aerosol Particles ◽  
Droplet Activation

Abstract. A calibration for LACIS (Leipzig Aerosol Cloud Interaction Simulator) for its use as a CCN (cloud condensation nuclei) detector has been developed. For this purpose, sodium chloride and ammonium sulfate particles of known sizes were generated and their grown sizes were detected at the LACIS outlet. From these signals, the effective critical super-saturation was derived as a function of the LACIS wall temperature. With this, LACIS is calibrated for its use as a CCN detector. The applicability of LACIS for measurements of the droplet activation, and also of the hygroscopic growth of atmospheric aerosol particles was tested. The activation of the urban aerosol particles used in the measurements was found to occur at a critical super-saturation of 0.46% for particles with a dry diameter of 75 nm, and at 0.42% for 85 nm, respectively. Hygroscopic growth was measured for atmospheric aerosol particles with dry diameters of 150, 300 and 350 nm at relative humidities of 98 and 99%, and it was found that the larger dry particles contained a larger soluble volume fraction of about 0.85, compared to about 0.6 for the 150 nm particles.

A condensation-growth and impaction method for rapid off-line chemical-characterization of organic submicrometer atmospheric aerosol particles

2003 ◽  
Vol 34 (2) ◽  
pp. 225-242 ◽  
Author(s):  
Berko Sierau ◽  
Frank Stratmann ◽  
Matthias Pelzing ◽  
Christian Neusüß ◽  
Diana Hofmann ◽  
...  
Keyword(s):  
Atmospheric Aerosol ◽  
Aerosol Particles ◽  
Chemical Characterization ◽  
Atmospheric Aerosol Particles ◽  
Condensation Growth

scholarly journals Determination of the refractive index of insoluble organic extracts from atmospheric aerosol over the visible wavelength range using optical tweezers

2018 ◽  
Vol 18 (8) ◽  
pp. 5235-5252 ◽  
Author(s):  
Rosalie H. Shepherd ◽  
Martin D. King ◽  
Amelia A. Marks ◽  
Neil Brough ◽  
Andrew D. Ward
Keyword(s):  
Refractive Index ◽  
Wavelength Range ◽  
Atmospheric Aerosol ◽  
Organic Aerosol ◽  
Angstrom Exponent ◽  
Organic Extracts ◽  
Ångström Exponent ◽  
Aqueous Core ◽  
Ångstrom Exponent ◽  
Real Refractive Index

Abstract. Optical trapping combined with Mie spectroscopy is a new technique used to record the refractive index of insoluble organic material extracted from atmospheric aerosol samples over a wide wavelength range. The refractive index of the insoluble organic extracts was shown to follow a Cauchy equation between 460 and 700 nm for organic aerosol extracts collected from urban (London) and remote (Antarctica) locations. Cauchy coefficients for the remote sample were for the Austral summer and gave the Cauchy coefficients of A = 1.467 and B = 1000 nm2 with a real refractive index of 1.489 at a wavelength of 589 nm. Cauchy coefficients for the urban samples varied with season, with extracts collected during summer having Cauchy coefficients of A=1.465±0.005 and B=4625±1200 nm2 with a representative real refractive index of 1.478 at a wavelength of 589 nm, whilst samples extracted during autumn had larger Cauchy coefficients of A = 1.505 and B = 600 nm2 with a representative real refractive index of 1.522 at a wavelength of 589 nm. The refractive index of absorbing aerosol was also recorded. The absorption Ångström exponent was determined for woodsmoke and humic acid aerosol extract. Typical values of the Cauchy coefficient for the woodsmoke aerosol extract were A=1.541±0.03 and B=14800±2900 nm2, resulting in a real refractive index of 1.584 ± 0.007 at a wavelength of 589 nm and an absorption Ångström exponent of 8.0. The measured values of refractive index compare well with previous monochromatic or very small wavelength range measurements of refractive index. In general, the real component of the refractive index increases from remote to urban to woodsmoke. A one-dimensional radiative-transfer calculation of the top-of-the-atmosphere albedo was applied to model an atmosphere containing a 3 km thick layer of aerosol comprising pure water, pure insoluble organic aerosol, or an aerosol consisting of an aqueous core with an insoluble organic shell. The calculation demonstrated that the top-of-the-atmosphere albedo increases by 0.01 to 0.04 for pure organic particles relative to water particles of the same size and that the top-of-the-atmosphere albedo increases by 0.03 for aqueous core-shell particles as volume fraction of the shell material increases to 25 %.

scholarly journals CARACTERIZAÇÃO ESPECTRAL DE PROPRIEDADES ÓPTICAS DE AEROSSÓIS EM REGIÃO DE FLORESTA TROPICAL

Nativa ◽  
2018 ◽  
Vol 6 (5) ◽  
pp. 451
Author(s):  
Jorge Almeida de Menezes ◽  
Rafael Da Silva Palácios ◽  
Evanízio Marinho Menezes Júnior ◽  
Amazonino Soares Júnior ◽  
José De Souza Nogueira
Keyword(s):  
Optical Properties ◽  
Global Network ◽  
Angstrom Exponent ◽  
The Earth ◽  
Forest Region ◽  
Ångström Exponent ◽  
Forest Regions ◽  
Suspended Dust ◽  
Ångstrom Exponent

Aerossóis atmosféricos desempenham um papel importante no equilíbrio de energia do sistema Terra-atmosfera. Medidas de aerossóis foram realizadas em área de floresta tropical utilizando fotômetro solar da rede global AERONET. Dados de 4 anos permitiram classificar as propriedades óticas dos aerossóis, definindo a climatologia para área de floresta tropical. Neste trabalho a profundidade óptica de aerossol (AOD) e expoente Ångström, α(440-870), foram utilizados para a análise espectral de aerossol. Médias de AOD(440nm) de 0,22 (±0,40), com média correspondente de α 1,27(±0,39).  A AOD(440nm) mostra picos distintos para estação seca e chuvosa, sendo que podem estar relacionados com padrões sazonais de aerossóis característicos dessas regiões. O α (440-870) apresentou modos de frequência que se relacionam com os principais tipos de aerossóis presentes em regiões de Floresta. Um cenário principal de aerossóis foi definido como aerossóis oriundos de queima de biomassa, com forte influência de fontes locais de aerossóis poluídos. Mistura de aerossóis estão presentes, enquanto que poeira em suspensão tem uma ocorrência pouco relevante.Palavras-chave: AOD, expoente Ångström, climatologia. SPECTRAL CHARACTERIZATION OF OPTICAL PROPERTIES OF AEROSOLS IN FOREST REGION ABSTRACT:Atmospheric aerosols play an important role in the energy balance of the Earth-atmosphere system. Aerosol measurements were performed in rainforest area, Manaus_Embrapa site using solar photometer from the AERONET global network. Data from 4 years allowed to classify the optical properties of the aerosols, defining the climatology for the site. In this work, the aerosol optical depth (AOD) and Ångström exponent, α (440-870), were used for aerosol spectral analysis. Mean AOD (440nm) of 0,22 (± 0.40), with corresponding mean of α 1,27 (± 0.39). AOD (440nm) shows distinct peaks for dry and rainy season, and may be related to seasonal aerosol patterns characteristic of these regions. The α (440-870) presented frequency modes that relate to the main types of aerosols present in Forest regions. A major aerosol scenario was defined as biomass-based aerosols, with strong influence from local sources of polluted aerosols. Mixtures of aerosols are present, while suspended dust has a slightly relevant occurrence.Keywords: AOD, Ångström exponent, climatology.

Characterization of individual atmospheric aerosol particles with SIMS and laser-SNMS

2006 ◽  
Vol 252 (19) ◽  
pp. 7006-7009 ◽  
Author(s):  
R.E. Peterson ◽  
A. Nair ◽  
S. Dambach ◽  
H.F. Arlinghaus ◽  
B.J. Tyler
Keyword(s):  
Atmospheric Aerosol ◽  
Aerosol Particles ◽  
Atmospheric Aerosol Particles

On the characterization of aerosols using the Ångström exponent in the Athens area

2006 ◽  
Vol 68 (18) ◽  
pp. 2147-2163 ◽  
Author(s):  
D.G. Kaskaoutis ◽  
H.D Kambezidis ◽  
A.D. Adamopoulos ◽  
P.A. Kassomenos
Keyword(s):  
Angstrom Exponent ◽  
Ångström Exponent ◽  
Athens Area ◽  
Ångstrom Exponent

scholarly journals Aerosol optical properties in a rural environment near the mega-city Guangzhou, China: implications for regional air pollution and radiative forcing

2008 ◽  
Vol 8 (2) ◽  
pp. 6845-6901 ◽  
Author(s):  
R. M. Garland ◽  
H. Yang ◽  
O. Schmid ◽  
D. Rose ◽  
A. Nowak ◽  
...  
Keyword(s):  
Optical Properties ◽  
Radiative Forcing ◽  
Aerosol Particles ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Particle Fraction ◽  
Angstrom Exponent ◽  
Ångström Exponent ◽  
532 Nm ◽  
Ångstrom Exponent

Abstract. The scattering and absorption of solar radiation by atmospheric aerosols is a key element of the Earth's radiative energy balance and climate. The optical properties of aerosol particles are, however, highly variable and not well characterized, especially near newly emerging mega-cities. In this study, aerosol optical properties were measured at a regional background site approximately 60 km northwest of the mega-city Guangzhou in southeast China. The measurements were part of the "Program of Regional Integrated Experiments of Air Quality over the Pearl River Delta" intensive campaign (PRIDE-PRD2006), covering the period of 1–30 July 2006. Scattering and absorption coefficients of dry aerosol particles with diameters up to 10 μm (PM10) were determined with a three-wavelength integrating nephelometer and with a photoacoustic spectrometer, respectively. Averaged over the measurement campaign (arithmetic mean ±standard deviation), the total scattering coefficients were 200±133 Mm−1 (450 nm), 151±103 Mm−1 (550 nm) and 104±72 Mm−1 (700 nm) and the absorption coefficient was 34.3±26.5 Mm−1 (532 nm). The average Ångström exponent was 1.46±0.21 (450 nm/700 nm) and the average single scattering albedo was 0.82±0.07 (532 nm) with minimum values as low as 0.5. The low single scattering albedo values indicate a high abundance of, as well as strong sources of light absorbing carbon (LAC). The ratio of LAC to CO concentration was highly variable throughout the campaign, indicating a complex mix of different combustion sources. The scattering and absorption coefficients, as well as the Ångström exponent and single scattering albedo, exhibited pronounced diurnal cycles, which can be attributed to boundary layer mixing effects and enhanced nighttime emissions of LAC (diesel soot from regulated truck traffic). The daytime average single scattering albedo of 0.87 appears to be more suitable for climate modeling purposes than the 24-h average of 0.82, as the latter value is strongly influenced by fresh emissions into a shallow nocturnal boundary layer. In spite of high photochemical activity during daytime, we found no evidence for strong local production of secondary aerosol mass. The relatively low average mass scattering efficiency with respect to PM10 (2.84±0.037 m2 g−1, λ=550 nm) indicates a high proportion of mass in the coarse particle fraction (diameter >1 μm). During high pollution episodes, however, the Ångström exponent exhibited a dependence on wavelength, which indicates an enhancement of the fine particle fraction during these periods. A negative correlation between single scattering albedo and backscatter fraction was observed and found to affect the impact that these parameters have on aerosol radiative forcing efficiency.

Sign in / Sign up

Export Citation Format

Share Document