Consistent determination of the heating rate of light-absorbing aerosol using wavelength- and time-dependent Aethalometer multiple-scattering correction

2021 ◽  
pp. 148277
Author(s):  
L. Ferrero ◽  
V. Bernardoni ◽  
L. Santagostini ◽  
S. Cogliati ◽  
F. Soldan ◽  
...  
Keyword(s):  
Heating Rate ◽  
Multiple Scattering ◽  
Time Dependent ◽  
Scattering Correction

scholarly journals Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: A multi-instrumental approach

2021 ◽  
Author(s):  
Jesús Yus-Díez ◽  
Vera Bernardoni ◽  
Griša Močnik ◽  
Andrés Alastuey ◽  
Davide Ciniglia ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Multiple Scattering ◽  
Correction Factor ◽  
Wavelength Dependence ◽  
Cross Sensitivity ◽  
Coated Glass ◽  
Mountain Station ◽  
Scattering Correction ◽  
Absorption Measurements

Abstract. Accurate measurements of light absorption by aerosolized particles, especially black carbon (BC), are of utter importance since BC represents the second most important climate-warming agent after carbon dioxide (CO2). Reducing the uncertainties related to the absorption measurement techniques will improve the global estimation of BC concentration and the radiative effects of light absorbing aerosols. Currently, one of the most widely used instruments for BC and absorption measurements is the dual-spot aethalometer, AE33, which derives the absorption coefficients of aerosol particles at 7 different wavelengths from the measurements of optical attenuation through a filter where particles are continuously collected. An accurate determination of the absorption coefficient relies on the quantification of non-linear processes related to the collection of sample on the filter. The multiple-scattering correction factor (C(λ)), which depends on the filter tape used and on the optical properties of the collected particles, is the parameter with the greatest uncertainty.An in-depth analysis of the AE33 multiple-scattering correction factor and its wavelength dependence for different filter tapes, i.e. the old most referenced known as TFE-coated glass and the current most widely used M8060, has been carried out by comparing the AE33 attenuation measurements with the absorption measurements from different filter-based techniques. Online co-located multi-angle absorption photometer (MAAP) measurements and offline PP_UniMI polar photometer measurements were used with this aim. We used data from three different measurement stations in North-East of Spain: an urban background station (Barcelona; BCN), a regional background station (Montseny; MSY) and a mountain-top station (Montsec d'Ares; MSA). The median C values (at 637 nm) measured at the three stations ranged between 2.29 (at BCN and MSY; lowest 5th percentile of 1.97 and highest 95th percentile of 2.68) and 2.51 (at MSA; lowest 5th percentile of 2.06 and highest 95th percentile of 3.06). The C factor was wavelength-dependent only at the mountain-top station, whereas at the urban and regional stations no statistically significant difference was found at the 7 different AE33 wavelengths. The wavelength-dependence of C at the mountain station was in part driven by the predominant effect of dust particles during Saharan dust outbreaks at this station. At the mountain station, neglecting the wavelength dependence of the C factor led to an underestimation of the Absorption Ångström Exponent (AAE) of 12 %. The analysis of the cross-sensitivity to scattering for different filter tapes revealed a large increase of the C factor at the three stations when the single scattering albedo (SSA) of the collected particles was above 0.90–0.95, with up to a 3-fold increase above the average values. The result of the cross-sensitivity to scattering displayed a fitted constant multiple scattering parameter, Cf, of 2.21 and 1.96 and a cross-sensitivity factor, ms, of 0.8 % and 1.7 % for MSY and MSA stations, respectively, for the TFE-coated glass filter tape. For the M8060 filter tape, Cf of 2.50, 1.96, 1.82 and a ms of 0.7 %, 1.5 %, 2.7 %, for BCN, MSY and MSA stations, respectively, were obtained. Differences in the absorption coefficient determined from AE33 measurements at BCN, MSY and MSA of around a 35–40 % can be expected when using the site-dependent C determined experimentally instead of the nominal C value.

Analysis of STEM micrographs of thick objects

1978 ◽  
Vol 36 (2) ◽  
pp. 106-107
Author(s):  
S. Golladay
Keyword(s):  
Inelastic Scattering ◽  
Multiple Scattering ◽  
Mass Distribution ◽  
Cross Sections ◽  
Phase Contrast ◽  
Image Point ◽  
Contrast Effects ◽  
Total Cross Sections ◽  
Elastic And Inelastic Scattering

The theory of multiple scattering has been worked out by Groves and comparisons have been made between predicted and observed signals for thick specimens observed in a STEM under conditions where phase contrast effects are unimportant. Independent measurements of the collection efficiencies of the two STEM detectors, calculations of the ratio σe/σi = R, where σe, σi are the total cross sections for elastic and inelastic scattering respectively, and a model of the unknown mass distribution are needed for these comparisons. In this paper an extension of this work will be described which allows the determination of the required efficiencies, R, and the unknown mass distribution from the data without additional measurements or models. Essential to the analysis is the fact that in a STEM two or more signal measurements can be made simultaneously at each image point.

scholarly journals Determination of time-dependent strengths of salt pillars based on strain energy principle

2019 ◽  
Vol 29 (2) ◽  
pp. 273-279 ◽  
Author(s):  
Prapasiri Junthong ◽  
Supattra Khamrat ◽  
Suratwadee Sartkaew ◽  
Kittitep Fuenkajorn
Keyword(s):  
Strain Energy ◽  
Time Dependent ◽  
Energy Principle

Measurement and Multiple Scattering Correction of K-Shell Ionization Cross Sections of Silver by Electron Impact

2001 ◽  
Vol 18 (4) ◽  
pp. 531-532 ◽  
Author(s):  
Zhou Chang-Geng ◽  
Fu Yu-Chuan ◽  
An Zhu ◽  
Tang Chang-Huan ◽  
Luo Zheng-Ming
Keyword(s):  
Electron Impact ◽  
Multiple Scattering ◽  
Cross Sections ◽  
Ionization Cross ◽  
Scattering Correction ◽  
Ionization Cross Sections ◽  
Shell Ionization
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