scholarly journals Investigating Wavelength-Dependent Aerosol Optical Properties Using Water Vapor Slant Column Retrievals from CLARS over the Los Angeles Basin

2016 ◽  
Author(s):  
Zhao-Cheng Zeng ◽  
Qiong Zhang ◽  
Jack S. Margolis ◽  
Run-Lie Shia ◽  
Sally Newman ◽  
...  
Keyword(s):  
Optical Properties ◽  
Water Vapor ◽  
Los Angeles ◽  
Near Infrared ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Aerosol Optical Properties ◽  
Absorption Bands ◽  
Novel Approach ◽  
Aerosol Scattering

Abstract. In this study, we propose a novel approach to constrain the optical properties of atmospheric aerosol in a complex urban environment using water vapor (H2O) slant column measurements in the near infrared. This approach is demonstrated using measurements from the California Laboratory for Atmospheric Remote Sensing Fourier Transform Spectrometer (CLARS-FTS) on the top of Mt. Wilson, California, and a two-stream-exact single scattering (2S-ESS) radiative transfer (RT) model. From the spectral measurements, we retrieve H2O slant column density (SCD) using 15 different absorption bands between 4000 and 8000 cm−1. Due to the wavelength dependence of aerosol scattering, large variations in H2O SCD retrievals are observed as a function of wavelength. Moreover, the variations are found to be correlated with aerosol optical depths (AOD) measured at the AERONET-Caltech station. Simulation results from the RT model reproduce this correlation and show that the aerosol scattering is the primary contributor to the variations in the wavelength dependence of the H2O SCD retrievals. The evidence from both measurements and simulations suggest that wavelength-dependent aerosol optical properties can be constrained using H2O retrievals from multiple bands.

scholarly journals Aerosol scattering effects on water vapor retrievals over the Los Angeles Basin

2017 ◽  
Vol 17 (4) ◽  
pp. 2495-2508 ◽  
Author(s):  
Zhao-Cheng Zeng ◽  
Qiong Zhang ◽  
Vijay Natraj ◽  
Jack S. Margolis ◽  
Run-Lie Shia ◽  
...  
Keyword(s):  
Water Vapor ◽  
Los Angeles ◽  
Greenhouse Gas ◽  
Atmospheric Aerosols ◽  
Near Infrared ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Absorption Bands ◽  
Aerosol Scattering ◽  
Scattering Effects

Abstract. In this study, we propose a novel approach to describe the scattering effects of atmospheric aerosols in a complex urban environment using water vapor (H2O) slant column measurements in the near infrared. This approach is demonstrated using measurements from the California Laboratory for Atmospheric Remote Sensing Fourier Transform Spectrometer on the top of Mt. Wilson, California, and a two-stream-exact single scattering (2S-ESS) radiative transfer (RT) model. From the spectral measurements, we retrieve H2O slant column density (SCD) using 15 different absorption bands between 4000 and 8000 cm−1. Due to the wavelength dependence of aerosol scattering, large variations in H2O SCD retrievals are observed as a function of wavelength. Moreover, the variations are found to be correlated with aerosol optical depths (AODs) measured at the AERONET-Caltech station. Simulation results from the RT model reproduce this correlation and show that the aerosol scattering effect is the primary contributor to the variations in the wavelength dependence of the H2O SCD retrievals. A significant linear correlation is also found between variations in H2O SCD retrievals from different bands and corresponding AOD data; this correlation is associated with the asymmetry parameter, which is a first-order measure of the aerosol scattering phase function. The evidence from both measurements and simulations suggests that wavelength-dependent aerosol scattering effects can be derived using H2O retrievals from multiple bands. This understanding of aerosol scattering effects on H2O retrievals suggests a promising way to quantify the effect of aerosol scattering on greenhouse gas retrievals and could potentially contribute towards reducing biases in greenhouse gas retrievals from space.

scholarly journals DIFFERENCES IN AEROSOL OPTICAL PROPERTIES AND CORRESPONDING RADIATIVE EFFECTS OF HAZE EVENTS BETWEEN SUMMER AND WINTER IN A MEGA-CITY OF CENTRAL CHINA

2018 ◽  
Vol XLII-3/W5 ◽  
pp. 25-31
Author(s):  
S. Jin ◽  
Y. Ma ◽  
Y. Jin ◽  
Y. Guan ◽  
M. Zhang
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Single Scattering ◽  
Central China ◽  
Back Trajectory ◽  
Aerosol Optical Properties ◽  
The North ◽  
Back Trajectory Analysis ◽  
Active Fire ◽  
Moderate Resolution Imaging Spectroradiometer

<p><strong>Abstract.</strong> Aerosol optical properties and corresponding radiative effect (ARE) in ultraviolet (UV), visible (VIS), near-infrared (NIR), and shortwave (SW) during haze periods between winter and summer of Wuhan were compared. With the development of haze, the average aerosol optical depth (AOD) increased from 0.34 to 0.79 in winter and from 0.64 to 1.36 in summer. The aerosol volume size distribution (ASD) showed that obvious increases in fine mode particles in both winter and summer with haze occurring. The single scattering albedo (SSA) increased significantly in both seasons as a result of the emergence of numerous non-absorbent aerosols when haze occurred. The ARE at UV, VIS, NIR, and SW changed in winter (summer) from &amp;minus;8.29 W/m<sup>2</sup> to &amp;minus;10.88 W/m<sup>2</sup> (&amp;minus;8.32 W/m<sup>2</sup> to &amp;minus;11.06 W/m<sup>2</sup>), from &amp;minus;43.26 W/m<sup>2</sup> to &amp;minus;66.04 W/m<sup>2</sup> (56.33 W/m<sup>2</sup> to &amp;minus;76.94 W/m<sup>2</sup>), from &amp;minus;21.90 W/m<sup>2</sup> to &amp;minus;44.57 W/m<sup>2</sup> (&amp;minus;31.36 W/m<sup>2</sup> to &amp;minus;48.67 W/m<sup>2</sup>), and from &amp;minus;73.46 W/m<sup>2</sup> to &amp;minus;119.49 W/m<sup>2</sup> (&amp;minus;8.32 W/m<sup>2</sup> to &amp;minus;11.06 W/m<sup>2</sup>) respectively, when air conditions changed from clear to hazy. The variations in ARE fraction of UV, VIS, and NIR in SW depended much more on particle size rather than SSA. The ARE fraction of UV and VIS decreased while it of NIR increased in SW, when haze developed. Back trajectory analysis with active fire areas from Moderate Resolution Imaging Spectroradiometer (MODIS) indicated that the BC originated from the North in summer, while active fires in winter were rare.</p>

scholarly journals Variability of aerosol optical properties in the Western Mediterranean Basin

2011 ◽  
Vol 11 (5) ◽  
pp. 14091-14125
Author(s):  
M. Pandolfi ◽  
M. Cusack ◽  
A. Alastuey ◽  
X. Querol
Keyword(s):  
Optical Properties ◽  
Sea Breeze ◽  
Single Scattering ◽  
Western Mediterranean ◽  
Aerosol Optical Properties ◽  
Air Masses ◽  
Aerosol Absorption ◽  
Western Mediterranean Basin ◽  
Aerosol Scattering ◽  
The Mean

Abstract. Aerosol light scattering, black carbon (BC) and particulate matter (PM) concentrations were measured at Montseny, a regional background site in the Western Mediterranean Basin (WMB) which is part of the European Supersite for Atmospheric Aerosol Research (EUSAAR). Off line analyses of 24 h PM filters collected with Hi-Vol instruments were performed for the determination of the main chemical components of PM. Measurements of BC were used to calculate the light absorption properties of atmospheric particles. Single Scattering Albedo (SSA) at 635 nm was estimated starting from aerosol scattering and absorption measurements, while Ångström exponents were calculated by means of the three wavelengths (450 nm, 525 nm, 635 nm) aerosol light scattering measurements from Nephelometer. Mean scattering and hemispheric backscattering coefficients (@ 635 nm) were 26.8 ± 23.3 Mm−1 and 4.3 ± 2.7 Mm−1, respectively and the mean aerosol absorption coefficient was 2.8 ± 2.2 Mm−1. Mean values of Single Scattering Albedo (SSA) and Ångström exponent (calculated from 450 nm to 635 nm) at MSY were 0.90 ± 0.05 and 1.2 ± 0.6, respectively. A clear relationship was observed between the PM1/PM10 and PM2.5/PM10 ratios as a function of the calculated Ångström exponents. Mass scattering cross sections for fine mass and sulfate at 635 nm were calculated in 2.8 ± 0.5 m2 g−1 and 11.8 ± 2.2 m2 g−1 respectively, while the mean aerosol absorption cross section was estimated around 10.4 ± 2.0 m2 g−1. The variability in aerosol optical properties in the WMB were largely explained by the origin and ageing of air masses over the measurement site. The sea breeze played an important role in transporting pollutants from the developed WMB coastlines towards inland rural areas, changing the optical properties of aerosols. Aerosol scattering and backscattering coefficients increased by around 40 % in the afternoon when the sea breeze was fully developed while the absorption coefficient increased by more than 100 % as a consequence of the increase in BC concentration at MSY observed under sea breeze circulation. The analysis of the Ångström (Å) exponent as a function of the origin the air masses revealed that polluted winter anticyclonic conditions and summer recirculation scenarios typical of the WMB led to an increase of fine particles in the atmosphere (Å = 1.4 ± 0.1) while the aerosol optical properties under Atlantic Advection episodes and Saharan dust outbreaks were clearly dominated by coarser particles (Å = 0.7 ± 0.3).

scholarly journals Determination and analysis of in situ spectral aerosol optical properties by a multi-instrumental approach

2014 ◽  
Vol 7 (8) ◽  
pp. 2373-2387 ◽  
Author(s):  
S. Segura ◽  
V. Estellés ◽  
G. Titos ◽  
H. Lyamani ◽  
M. P. Utrillas ◽  
...  
Keyword(s):  
Optical Properties ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Aerosol Optical Properties ◽  
Absorption Coefficients ◽  
Instrumental Approach ◽  
Loading Effects ◽  
Absorption Photometer ◽  
Integrating Nephelometer

Abstract. Continuous in situ measurements of aerosol optical properties were conducted from 29 June to 29 July 2012 in Granada (Spain) with a seven-wavelength Aethalometer, a Multi-Angle Absorption Photometer, and a three-wavelength integrating nephelometer. The aim of this work is to describe a methodology to obtain the absorption coefficients (babs) for the different Aethalometer wavelengths. In this way, data have been compensated using algorithms which best estimate the compensation factors needed. Two empirical factors are used to infer the absorption coefficients from the Aethalometer measurements: C – the parameter describing the enhancement of absorption by particles in the filter matrix due to multiple scattering of light in the filter matrix – and f, the parameter compensating for non-linear loading effects in the filter matrix. Spectral dependence of f found in this study is not very strong. Values for the campaign lie in the range from 1.15 at 370 nm to 1.11 at 950 nm. Wavelength dependence in C proves to be more important, and also more difficult to calculate. The values obtained span from 3.42 at 370 nm to 4.59 at 950 nm. Furthermore, the temporal evolution of the Ångström exponent of absorption (αabs) and the single-scattering albedo (ω0) is presented. On average αabs is around 1.1 ± 0.3, and ω0 is 0.78 ± 0.08 and 0.74 ± 0.09 at 370 and 950 nm, respectively. These are typical values for sites with a predominance of absorbing particles, and the urban measurement site in this study is such. The babs average values are of 16 ± 10 Mm−1 (at 370 nm) and 5 ± 3 Mm−1 (at 950 nm), respectively. Finally, differences between workdays and Sundays have been further analysed, obtaining higher babs and lower ω0 during the workdays than on Sundays as a consequence of the diesel traffic influence.

scholarly journals Determination and analysis of spectral aerosol optical properties by a multi-instrumental approach

2014 ◽  
Vol 7 (2) ◽  
pp. 1871-1916
Author(s):  
S. Segura ◽  
V. Estellés ◽  
G. Titos ◽  
H. Lyamani ◽  
M. P. Utrillas ◽  
...  
Keyword(s):  
Optical Properties ◽  
Wavelength Dependence ◽  
Single Scattering ◽  
Aerosol Optical Properties ◽  
Absorption Coefficients ◽  
Instrumental Approach ◽  
Loading Effects ◽  
Absorption Photometer ◽  
Integrating Nephelometer

Abstract. Continuous in-situ measurements of aerosol optical properties where conducted from 20 June to 20 July in Granada (Spain) with a 7-wavelength Aethalometer, a Multi Angle Absorption Photometer, and a 3-wavelength integrating Nephelometer. The aim of this work is to describe a methodology to obtain the absorption coefficients (babs) for the different Aethalometer wavelengths. In this way, data have been compensated using algorithms which best estimate the compensation factors needed. Two empirical factors are used to infer the absorption coefficients from the Aethalometer measurements: C – the parameter describing the enhancement of absorption by particles in the filter matrix due to multiple scattering of light in the filter matrix; and f – the parameter compensating for non-linear loading effects in the filter matrix. Spectral dependence of f found in this study is not very strong. Values for the campaign lie in the range from 1.15 at 370 nm to 1.11 at 950 nm. Wavelength dependence in C proves to be more important, and also more difficult to calculate. The values obtained span from 3.40 at 370 nm to 4.35 at 950 nm. Furthermore, the temporal evolution of the Ångström exponent of absorption (αabs) and the single scattering albedo (ω0), is presented. On average αabs is around 1.1 ± 0.3, and ω0 is 0.78 ± 0.08 and 0.74 ± 0.09 at 370 and 950 nm, respectively. These are typical values for sites with a predominance of absorbing particles, and the urban measurement site in this study is such. The babs average values are of 16 ± 10 Mm−1 (at 370 nm) and 5 ± 3 Mm−1 (at 950 nm), respectively. Finally, differences between working days and Sunday have been further analyzed, obtaining higher babs and lower ω0 during week than on Sundays as a consequence of the influence of diesel traffic.

Aerosol optical properties and precipitable water vapor column in the atmosphere of Norway

2015 ◽  
Vol 54 (6) ◽  
pp. 1505 ◽  
Author(s):  
Dennis Muyimbwa ◽  
Øyvind Frette ◽  
Jakob J. Stamnes ◽  
Taddeo Ssenyonga ◽  
Yi-Chun Chen ◽  
...  
Keyword(s):  
Optical Properties ◽  
Water Vapor ◽  
Precipitable Water ◽  
Precipitable Water Vapor ◽  
Aerosol Optical Properties

Structure and microstructure of near infrared-absorbing Au–Au2S nanoparticles

2007 ◽  
Vol 22 (9) ◽  
pp. 2531-2538 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow
Keyword(s):  
Optical Properties ◽  
Surface Segregation ◽  
Near Infrared ◽  
Small Degree ◽  
Core Shell ◽  
Shell Microstructure ◽  
Absorption Bands ◽  
Interfacial Effects ◽  
Nir Absorption ◽  
Structure And Microstructure

Near infrared (NIR) absorbing nanoparticles synthesized by the reduction of HAuCl4 with Na2S exhibited absorption bands at ∼530 nm, and in the NIR region of 650–1100 nm. The NIR optical properties were not found to be related to the earlier proposed Au2S–Au core-shell microstructure in previous studies. From a detailed study of the structure and microstructure of as-synthesized particles in this work, S-containing, Au-rich, multiply-twinned nanoparticles were found to exhibit NIR absorption. They consisted of amorphous AuxS (where x = 2), mostly well mixed within crystalline Au, with a small degree of surface segregation of S. Therefore, NIR absorption was likely due to interfacial effects on particle polarization from the introduction of AuxS into Au particles, and not the dielectric confinement of plasmons associated with a core-shell microstructure.

Composition, particle size, and near-infrared irradiation effects on optical properties of Au–Au2S nanoparticles

2008 ◽  
Vol 23 (1) ◽  
pp. 281-293 ◽  
Author(s):  
Mei Chee Tan ◽  
Jackie Y. Ying ◽  
Gan Moog Chow
Keyword(s):  
Particle Size ◽  
Optical Properties ◽  
Thermal Effects ◽  
Near Infrared ◽  
Sodium Sulfide ◽  
Irradiation Effects ◽  
Absorption Bands ◽  
Molar Ratios ◽  
Nir Absorption ◽  
Structure And Microstructure

Near-infrared (NIR)-absorbing nanoparticles synthesized by the reduction of tetrachloroauric acid (HAuCl4) using sodium sulfide (Na2S) exhibited absorption bands at ∼530 nm and at the NIR region of 650−1100 nm. A detailed study on the structure and microstructure of as-synthesized nanoparticles was reported previously. The as-synthesized nanoparticles were found to consist of amorphous AuxS (x = ∼2), mostly well mixed within crystalline Au. In this work, the optical properties were tailored by varying the precursor molar ratios of HAuCl4 and Na2S. In addition, a detailed study of composition and particle-size effects on the optical properties was discussed. The change of polarizability by the introduction of S in the form of AuxS (x = ∼2) had a significant effect on NIR absorption. Also, it was found in this work that exposure of these particles to NIR irradiation using a Nd:YAG laser resulted in loss of the NIR absorption band. Thermal effects generated during NIR irradiation had led to microstructural changes that modified the optical properties of particles.

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

2012 ◽  
Vol 12 (12) ◽  
pp. 5647-5659 ◽  
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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