scholarly journals Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source

2013 ◽  
Vol 6 (4) ◽  
pp. 6293-6327 ◽  
Author(s):  
N. Sharma ◽  
I. J. Arnold ◽  
H. Moosmüller ◽  
W. P. Arnott ◽  
C. Mazzoleni
Keyword(s):  
Optical Properties ◽  
Light Source ◽  
Wavelength Dependence ◽  
Common Salt ◽  
Design Development ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Multi Wavelength

Abstract. A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands were selected from the continuous spectrum of the laser (ranging from 400–2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

scholarly journals Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source

2013 ◽  
Vol 6 (12) ◽  
pp. 3501-3513 ◽  
Author(s):  
N. Sharma ◽  
I. J. Arnold ◽  
H. Moosmüller ◽  
W. P. Arnott ◽  
C. Mazzoleni
Keyword(s):  
Optical Properties ◽  
Light Source ◽  
Wavelength Dependence ◽  
Common Salt ◽  
Design Development ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption ◽  
Multi Wavelength

Abstract. A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands are selected from the continuous spectrum of the laser (ranging from 400–2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

scholarly journals Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability

2010 ◽  
Vol 10 (1) ◽  
pp. 239-254 ◽  
Author(s):  
H. Lyamani ◽  
F. J. Olmo ◽  
L. Alados-Arboledas
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Seasonal Cycle ◽  
Large Fraction ◽  
Particle Diameter ◽  
Urban Site ◽  
Number Density ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption

Abstract. Measurements of aerosol optical properties and aerosol number size distribution obtained during the period from December 2005 to November 2007 at Granada, an urban site in south-eastern Spain, are analyzed. Large variations of the measured variables have been found, and related to variations in emissions sources and meteorological conditions. High values of aerosol absorption and scattering coefficients are obtained during winter and low values are measured during summer. This seasonal pattern in the surface aerosol optical properties is opposite to the seasonal cycle showed by columnar aerosol optical depth. The differences in the seasonal features of the surface and column-integrated data are related to seasonal variations in the aerosol vertical distribution, aerosol sources and boundary layer height. In winter the number density of "fine" particles (0.5<particle diameter<1 μm) is significantly larger than in summer while the number density of "coarse" particles (1<particle diameter<20 μm) is slightly larger during summer and spring than during winter and autumn. The scattering Angström exponent, αs, presents an evident seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and 1.4±0.3 in winter, spring, summer and autumn, respectively. This suggests the presence of a large fraction of submicron particles at the site, especially during winter. The aerosols measured in this study contain a large fraction of absorbing material as indicated by the average single-scattering albedo that has values of 0.65±0.07, 0.66±0.06, 0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer, respectively. The aerosol scattering albedo obtained in the surface boundary layer of Granada is below the critical value of 0.86 that determines the shift from cooling to warming. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosols only. The aerosol absorption and scattering coefficients present a clear diurnal pattern, in all seasons, with two local maxima, one early in the morning and the second one in the evening. This diurnal cycle is mainly attributed to the diurnal evolution of atmospheric boundary layer and local anthropogenic activities.

scholarly journals Physical and optical properties of aerosols over an urban location in Spain: seasonal and diurnal variability

2009 ◽  
Vol 9 (5) ◽  
pp. 18159-18199 ◽  
Author(s):  
H. Lyamani ◽  
F. J. Olmo ◽  
L. Alados-Arboledas
Keyword(s):  
Boundary Layer ◽  
Optical Properties ◽  
Seasonal Cycle ◽  
Large Fraction ◽  
Particle Diameter ◽  
Urban Site ◽  
Number Density ◽  
Aerosol Optical Properties ◽  
Scattering Coefficients ◽  
Aerosol Absorption

Abstract. Measurements of aerosol optical properties and aerosol number size distribution obtained during the period from December 2005 to November 2007 at Granada, an urban site in south-eastern Spain, are analyzed. Large variations of the measured variables have been found, and related to variations in emissions sources and meteorological conditions. High values of aerosol absorption and scattering coefficients are obtained during winter and low values are measured during summer. This seasonal pattern in the surface aerosol optical properties is opposite to the seasonal cycle showed by columnar aerosol optical depth. The differences in the seasonal features of the surface and column-integrated data are related to seasonal variations in the aerosol vertical distribution, aerosol sources and boundary layer height. In winter the number density of fine particles (0.5<particle diameter<1μm) is significantly larger than in summer while the number density of coarse particles (1<particle diameter<20 μm) is slightly larger during summer and spring than during winter and autumn. The scattering Angström exponent, αs, presents an evident seasonal cycle with values of 1.8±0.2, 1.6±0.3, 1.3±0.3 and 1.4±0.3 in winter, spring, summer and autumn, respectively. This suggests the presence of a large fraction of submicron particles at the site, especially during winter. Urban aerosols in Granada contain a large fraction of absorbing material as indicated by the average single-scattering albedo that has values of 0.65±0.07, 0.66±0.06, 0.70±0.06 and 0.73±0.06 in autumn, winter, spring and summer, respectively. The aerosol scattering albedo obtained in the surface boundary layer of Granada is below the critical value of 0.86 that determines the shift from cooling to warming. These results put in evidence the need of efforts to reduce absorbing particles (black carbon) emissions to avoid the possible warming that would result from the reductions of the cooling aerosols only. The aerosol absorption and scattering coefficients present a clear diurnal pattern, in all seasons, with two local maxima, one early in the morning and the second one in the evening. This diurnal cycle is mainly attributed to the diurnal evolution of atmospheric boundary layer and local anthropogenic activities.

scholarly journals Chemical apportionment of southern African aerosol mass and optical depth

2009 ◽  
Vol 9 (19) ◽  
pp. 7643-7655 ◽  
Author(s):  
B. I. Magi
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Cross Sections ◽  
Southern Africa ◽  
Climate Models ◽  
Critical Role ◽  
Carbonaceous Aerosol ◽  
Aerosol Optical Properties ◽  
Aerosol Absorption ◽  
Aerosol Mass

Abstract. This study characterizes the aerosol over extratropical and tropical southern Africa during the biomass burning season by presenting an aerosol mass apportionment and aerosol optical properties. Carbonaceous aerosol species account for 54% and 83% of the extratropical and tropical aerosol mass, respectively, which is consistent with the fact that the major source of particulate matter in southern Africa is biomass burning. This mass apportionment implies that carbonaceous species in the form of organic carbon (OC) and black carbon (BC) play a critical role in the aerosol optical properties. By combining the in situ measurements of aerosol mass concentrations with concurrent measurements of aerosol optical properties at a wavelength of 550 nm, it is shown that 80–90% of the aerosol scattering is due to carbonaceous aerosol, and the derived mass scattering cross sections (MSC) for OC and BC are 3.9±0.6 m2/g and 1.6±0.2 m2/g, respectively. Derived values of mass absorption cross sections (MAC) for OC and BC are 0.7±0.6 m2/g and 8.2±1.1 m2/g, respectively. The values of MAC imply that ~26% of the aerosol absorption in southern Africa is due to OC, with the remainder due to BC. The results in this study provide important constraints for aerosol properties in a region dominated by biomass burning and should be integrated into climate models to improve aerosol simulations.

Characterization of aerosol optical properties and model computed radiative forcing over a semi-arid region, Kadapa in India

2018 ◽  
Vol 209 ◽  
pp. 36-49 ◽  
Author(s):  
C. Viswanatha Vachaspati ◽  
G. Reshma Begam ◽  
Y. Nazeer Ahammed ◽  
K. Raghavendra Kumar ◽  
R.R. Reddy
Keyword(s):  
Optical Properties ◽  
Arid Region ◽  
Radiative Forcing ◽  
Aerosol Optical Properties ◽  
Semi Arid Region ◽  
Semi Arid

scholarly journals Simultaneous observations by sky radiometer and MAX-DOAS for characterization of biomass burning plumes in central Thailand in January–April 2016

2019 ◽  
Vol 12 (1) ◽  
pp. 599-606 ◽  
Author(s):  
Hitoshi Irie ◽  
Hossain Mohammed Syedul Hoque ◽  
Alessandro Damiani ◽  
Hiroshi Okamoto ◽  
Al Mashroor Fatmi ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Surface Concentration ◽  
Wavelength Dependence ◽  
Optical Absorption Spectroscopy ◽  
Near Surface ◽  
Aerosol Absorption ◽  
Volatile Organic Compound Emissions ◽  
Carbon Aerosols ◽  
Central Thailand

Abstract. The first intensive multicomponent ground-based remote-sensing observations by sky radiometer and multi-axis differential optical absorption spectroscopy (MAX-DOAS) were performed simultaneously at the SKYNET Phimai site located in central Thailand (15.18∘ N, 102.56∘ E) from January to April 2016. The period corresponds to the dry season associated with intense biomass burning (BB) activity around the site. The near-surface concentration of formaldehyde (HCHO) retrieved from MAX-DOAS was found to be a useful tracer for absorption aerosols from BB plumes, when BB was the dominant source of HCHO and absorption aerosols over other sources. As the HCHO concentration tripled from 3 to 9 ppbv, the ratio of gaseous glyoxal to HCHO concentrations in daytime decreased from ∼0.04 to ∼0.03, responding presumably to the increased contribution of volatile organic compound emissions from BB. In addition, clear increases in aerosol absorption optical depths (AAODs) retrieved from sky radiometer observations were seen with the HCHO enhancement. At a HCHO of 9 ppbv, AAOD at a wavelength of 340 nm reached as high as ∼0.15±0.03. The wavelength dependence of AAODs at 340–870 nm was quantified by the absorption Ångström exponent (AAE), providing evidence for the presence of brown carbon aerosols at an AAE of 1.5±0.2. Thus, our multicomponent observations around central Thailand are expected to provide unique constraints for understanding physical–chemical–optical properties of BB plumes.

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