scholarly journals Development of a cavity-enhanced aerosol albedometer

2014 ◽  
Vol 7 (8) ◽  
pp. 2551-2566 ◽  
Author(s):  
W. Zhao ◽  
X. Xu ◽  
M. Dong ◽  
W. Chen ◽  
X. Gu ◽  
...  
Keyword(s):  
Spectral Region ◽  
Single Channel ◽  
Single Scattering ◽  
Polystyrene Latex ◽  
Integrating Sphere ◽  
Instrumental Performance ◽  
Optical Extinction ◽  
Extinction Coefficients ◽  
Enhanced Absorption ◽  
Aerosol Scattering

Abstract. We report on the development of a cavity-enhanced aerosol single-scattering albedometer based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) combined with an integrating sphere (IS) for simultaneous in situ measurements of aerosol scattering and extinction coefficients in an exact same sample volume. The cavity-enhanced albedometer employed a blue light-emitting-diode (LED)-based IBBCEAS approach for the measurement of wavelength-resolved aerosol optical extinction over the spectral range of 445–480 nm and an integrating sphere nephelometer coupled to the IBBCEAS setup for the measurement of aerosol scattering. The scattering signal was measured with a single-channel photomultiplier tube (PMT), providing an averaged value over a narrow bandwidth (full-width at half-maximum, FWHM, ~ 9 nm) in the spectral region of 465–474 nm. A scattering coefficient at a wavelength of 470 nm was deduced as an averaged scattering value over the spectral region of 465–474 nm and used for data analysis and instrumental performance comparison. Performance evaluation of the albedometer was carried out using laboratory-generated particles and ambient aerosol. The scattering and extinction measurements of monodisperse polystyrene latex (PSL) spheres generated in the laboratory proved excellent correlation between two channels of the albedometer. The retrieved refractive index (RI) of the PSL particles from the measured scattering and extinction efficiencies agreed well with the values reported in previously published papers. Aerosol light scattering and extinction coefficients, single-scattering albedo (SSA) and NO2 concentrations in an ambient sample were directly and simultaneously measured using the albedometer developed. The instrument developed was validated via an intercomparison of the measured aerosol scattering coefficients and NO2 trace gas concentrations to a TSI 3563 integrating nephelometer and a chemiluminescence detector, respectively.

scholarly journals Development of a cavity enhanced aerosol albedometer

2014 ◽  
Vol 7 (3) ◽  
pp. 2981-3019
Author(s):  
W. Zhao ◽  
X. Xu ◽  
M. Dong ◽  
W. Chen ◽  
X. Gu ◽  
...  
Keyword(s):  
Single Channel ◽  
Broad Band ◽  
Single Scattering ◽  
Polystyrene Latex ◽  
Scattering Coefficient ◽  
Integrating Sphere ◽  
Instrumental Performance ◽  
Optical Extinction ◽  
Extinction Coefficients ◽  
Aerosol Scattering

Abstract. We report on the development of a cavity enhanced aerosol single scattering albedometer incorporating incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach and an integrating sphere (IS) for simultaneous in situ measurements of aerosol scattering and extinction coefficients in the exact same sample volume. The cavity enhanced albedometer employed a blue light-emitting diode (LED) based IBBCEAS approach for the measurement of wavelength-resolved aerosol optical extinction over the spectral range of 445–480 nm. An integrating sphere nephelometer coupled to the IBBCEAS setup was used for the measurement of aerosol scattering. The scattering signal was measured with a single channel photomultiplier tube (PMT), providing an integrated value over a narrow bandwidth (FWHM ~ 9 nm) in the spectral region of 465–474 nm. A scattering coefficient at a wavelength of 470 nm was deduced as an averaged scattering value and used for data analysis and instrumental performance comparison. Performance evaluation of the albedometer was carried out using laboratory-generated particles and ambient aerosol. The scattering and extinction measurements of monodisperse polystyrene latex (PSL) spheres generated in laboratory proved excellent correlation between two channels of the albedometer. The retrieved refractive index (RI) from the measured scattering and extinction efficiencies agreed well with the values reported in previously published papers. Aerosol light scattering and extinction coefficients, single scattering albedo (SSA) and NO2 concentrations in an ambient sample were directly and simultaneously measured using the developed albedometer. The developed instrument was validated via an intercomparison of the measured aerosol scattering coefficient and NO2 trace concentration against a TSI 3563 integrating nephelometer and a chemiluminescence detector, respectively.

scholarly journals Technical Note: Simple analytical relationships between Ångström coefficients of aerosol extinction, scattering, absorption, and single scattering albedo

2011 ◽  
Vol 11 (7) ◽  
pp. 19213-19222 ◽  
Author(s):  
H. Moosmüller ◽  
R. K. Chakrabarty
Keyword(s):  
Wavelength Dependence ◽  
Single Scattering ◽  
Technical Note ◽  
Single Scattering Albedo ◽  
Experimental Results ◽  
Aerosol Extinction ◽  
Extinction Coefficients ◽  
Physical Understanding ◽  
Aerosol Scattering

Abstract. Ångström coefficients are commonly used to parameterize the slow wavelength dependence of aerosol scattering, absorption, and extinction coefficients and single scattering albedo. Here we introduce simple analytical relationships between these coefficients that establish a framework for intercomparison between theory and experimental results from different instruments and platforms and allow for closure studies and improved physical understanding.

scholarly journals Technical Note: Simple analytical relationships between Ångström coefficients of aerosol extinction, scattering, absorption, and single scattering albedo

2011 ◽  
Vol 11 (20) ◽  
pp. 10677-10680 ◽  
Author(s):  
H. Moosmüller ◽  
R. K. Chakrabarty
Keyword(s):  
Wavelength Dependence ◽  
Single Scattering ◽  
Technical Note ◽  
Single Scattering Albedo ◽  
Experimental Results ◽  
Aerosol Extinction ◽  
Extinction Coefficients ◽  
Physical Understanding ◽  
Aerosol Scattering

Abstract. Ångström coefficients are commonly used to parameterize the slow wavelength dependence of aerosol scattering, absorption, and extinction coefficients and single scattering albedo. Here we introduce simple analytical relationships between these coefficients that establish a framework for intercomparison between theory and experimental results from different instruments and platforms and allow for closure studies and improved physical understanding.

scholarly journals Quantifying the impact of aerosol scattering on the retrieval of methane from airborne remote sensing measurements

2020 ◽  
Vol 13 (12) ◽  
pp. 6755-6769
Author(s):  
Yunxia Huang ◽  
Vijay Natraj ◽  
Zhao-Cheng Zeng ◽  
Pushkar Kopparla ◽  
Yuk L. Yung
Keyword(s):  
Remote Sensing ◽  
Surface Albedo ◽  
Single Scattering ◽  
Water Soluble ◽  
Transfer Model ◽  
Background Values ◽  
Ch4 Emissions ◽  
Aerosol Scattering ◽  
The Impact ◽  
Retrieval Bias

Abstract. As a greenhouse gas with strong global warming potential, atmospheric methane (CH4) emissions have attracted a great deal of attention. Although remote sensing measurements can provide information about CH4 sources and emissions, accurate retrieval is challenging due to the influence of atmospheric aerosol scattering. In this study, imaging spectroscopic measurements from the Airborne Visible/Infrared Imaging Spectrometer – Next Generation (AVIRIS-NG) in the shortwave infrared are used to compare two retrieval techniques – the traditional matched filter (MF) method and the optimal estimation (OE) method, which is a popular approach for trace gas retrievals. Using a numerically efficient radiative transfer model with an exact single-scattering component and a two-stream multiple-scattering component, we also simulate AVIRIS-NG measurements for different scenarios and quantify the impact of aerosol scattering in the two retrieval schemes by including aerosols in the simulations but not in the retrievals. The presence of aerosols causes an underestimation of CH4 in both the MF and OE retrievals; the biases increase with increasing surface albedo and aerosol optical depth (AOD). Aerosol types with high single-scattering albedo and low asymmetry parameter (such as water-soluble aerosols) induce large biases in the retrieval. When scattering effects are neglected, the MF method exhibits lower fractional retrieval bias compared to the OE method at high CH4 concentrations (2–5 times typical background values) and is suitable for detecting strong CH4 emissions. For an AOD value of 0.3, the fractional biases of the MF retrievals are between 1.3 % and 4.5 %, while the corresponding values for OE retrievals are in the 2.8 %–5.6 % range. On the other hand, the OE method is an optimal technique for diffuse sources (<1.5 times typical background values), showing up to 5 times smaller fractional retrieval bias (8.6 %) than the MF method (42.6 %) for the same AOD scenario. However, when aerosol scattering is significant, the OE method is superior since it provides a means to reduce biases by simultaneously retrieving AOD, surface albedo, and CH4. The results indicate that, while the MF method is good for plume detection, the OE method should be employed to quantify CH4 concentrations, especially in the presence of aerosol scattering.

scholarly journals Atmospheric radiative effects of an in-situ measured Saharan dust plume and the role of large particles

2007 ◽  
Vol 7 (3) ◽  
pp. 7767-7817 ◽  
Author(s):  
S. Otto ◽  
M. de Reus ◽  
T. Trautmann ◽  
A. Thomas ◽  
M. Wendisch ◽  
...  
Keyword(s):  
Complex Refractive Index ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Saharan Dust ◽  
Dust Particles ◽  
Modal Parameters ◽  
Size Distributions ◽  
Radiative Effects ◽  
Enhanced Absorption ◽  
Large Particles

Abstract. This work will present aerosol size distributions measured in a Saharan dust plume between 0.9 and 12 km altitude during the ACE-2 campaign 1997. The distributions contain a significant fraction of large particles of diameters from 4 to 30 μm. Radiative transfer calculations have been performed using these data as input. Shortwave, longwave as well as total atmospheric radiative effects (AREs) of the dust plume are investigated over ocean and desert within the scope of sensitivity studies considering varied input parameters like solar zenith angle, scaled total dust optical depth, tropospheric standard aerosol profiles and particle complex refractive index. The results indicate that the large particle fraction has a predominant impact on the optical properties of the dust. A single scattering albedo of ωo=0.75–0.96 at 550 nm was simulated in the entire dust column as well as 0.76 within the Saharan dust layer at ~4 km altitude indicating enhanced absorption. The measured dust leads to cooling over the ocean but warming over the desert due to differences in their spectral surface albedo and surface temperature. The large particles absorb strongly and they contribute at least 20% to the ARE in the dusty atmosphere. From the measured size distributions modal parameters of a bimodal lognormal column volume size distribution were deduced, resulting in a coarse median diameter of ~9 μm and a column single scattering albedo of 0.78 at 550 nm. A sensitivity study demonstrates that variabilities in the modal parameters can cause completely different AREs and emphasises the warming effect of the large mineral dust particles.

scholarly journals Vertical profiles of sub-micron aerosol single scattering albedo over Indian region immediately before monsoon onset and during its development: Research from the SWAAMI field campaign

2019 ◽  
Author(s):  
Mohanan R. Manoj ◽  
Sreedharan K. Satheesh ◽  
Krishnaswamy K. Moorthy ◽  
Hugh Coe
Keyword(s):  
Active Phase ◽  
Single Scattering ◽  
Single Scattering Albedo ◽  
Development Research ◽  
Aerosol Absorption ◽  
South West ◽  
Aerosol Scattering ◽  
First Time ◽  
Geographical Locations

Abstract. Vertical structures of aerosol single scattering albedo (SSA), from near the surface through the free troposphere, have been estimated for the first time at distinct geographical locations over the Indian mainland and adjoining oceans, using in-situ measurements of aerosol scattering and absorption coefficients aboard the FAAM BAe-146 aircraft during the South West Asian Aerosol Monsoon Interactions (SWAAMI) campaign from June to July 2016. These are used to examine the spatial variation of SSA profiles and also to characterize its transformation from just prior to the onset of Indian Summer Monsoon (June 2016) to its active phase (July 2016). Very strong aerosol absorption, with SSA values as low as 0.7, persisted in the lower altitudes (

scholarly journals Seasonal distribution of aerosol properties over Europe and their impact on UV irradiance

2009 ◽  
Vol 2 (4) ◽  
pp. 1863-1899
Author(s):  
N. Y. Chubarova
Keyword(s):  
Optical Thickness ◽  
Spectral Region ◽  
Single Scattering ◽  
Temporal Variations ◽  
Aerosol Optical Thickness ◽  
Asymmetry Factor ◽  
Uv Irradiance ◽  
Aerosol Parameters ◽  
Radiative Transfer Modeling

Abstract. Using the aerosol optical thickness at 550 nm (τ550) from MODIS (collection 5) combined with the aerosol products from the ground-based AERONET network, key aerosol parameters have been obtained with 1 degree resolution over Europe. Additional tests have revealed a satisfactory quality of the MODIS data, except in a few cases. Quality assured AERONET data are used for evaluating the Angstrom exponent, single scattering albedo and asymmetry factor, and for validating the final aerosol optical thickness in the UV spectral region. A method for extrapolating the aerosol parameters into the UV spectral region is discussed. The aerosol optical thickness distributions are considered together with meteorological fields from NOAA_NCEP_CPC_CAMS_OPI climatology. The τ340 is shown to vary significantly from approximately 0.01 to 0.9 depending on the season and location. Permanent elevated aerosol loading over several industrial areas is observed, which agrees with the output of chemical transport models. Using radiative transfer modeling, monthly mean UV loss due to aerosol was estimated. The absolute decrease in UV indices varies from less than 0.1 to 1.5. The relative UV attenuation has large spatial and temporal variations (from −1% to −17%) with a minimum towards the northwest and maxima over several southern local areas (Northern Italy, etc.) during the warm period.

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