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
<p>Providing reliable observations of aerosol particles' absorption properties at spatial and temporal resolutions suited to climate models is of utter importance to better understand the effects that atmospheric particles have on climate. Nowadays, one of the instruments most widely used...
| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2021-10-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://amt.copernicus.org/articles/14/6335/2021/amt-14-6335-2021.pdf |
| _version_ | 1819290913102364672 |
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| author | J. Yus-Díez J. Yus-Díez V. Bernardoni G. Močnik G. Močnik A. Alastuey D. Ciniglia M. Ivančič X. Querol N. Perez C. Reche M. Rigler R. Vecchi S. Valentini M. Pandolfi |
| author_facet | J. Yus-Díez J. Yus-Díez V. Bernardoni G. Močnik G. Močnik A. Alastuey D. Ciniglia M. Ivančič X. Querol N. Perez C. Reche M. Rigler R. Vecchi S. Valentini M. Pandolfi |
| author_sort | J. Yus-Díez |
| collection | DOAJ |
| description | <p>Providing reliable observations of aerosol particles' absorption properties at spatial and temporal resolutions suited to climate models is of utter importance to better understand the effects that atmospheric particles have on climate. Nowadays, one of the instruments most widely used in international monitoring networks for in situ surface measurements of light absorption properties of atmospheric aerosol particles is the multi-wavelength dual-spot Aethalometer, AE33. The AE33 derives the absorption coefficients of aerosol particles at seven different wavelengths from the measurements of the optical attenuation of light through a filter where particles are continuously collected. An accurate determination of the absorption coefficients from the AE33 instrument relies on the quantification of the non-linear processes related to the sample collection on the filter. The multiple-scattering correction factor (<span class="inline-formula"><i>C</i></span>), which depends on the filter tape used and on the optical properties of the collected particles, is the parameter with both the greatest uncertainty and the greatest impact on the absorption coefficients derived from the AE33 measurements.</p>
<p>Here we present an in-depth analysis of the AE33 multiple-scattering correction factor <span class="inline-formula"><i>C</i></span> and its wavelength dependence for two different and widely used filter tapes, namely the old, and most referenced, TFE-coated glass, or M8020, filter tape and the currently, and most widely used, M8060 filter tape. For performing this analysis, we compared the attenuation measurements from AE33 with the absorption coefficients measured with different filter-based techniques. On-line co-located multi-angle absorption photometer (MAAP) measurements and off-line PP_UniMI polar photometer measurements were employed as reference absorption measurements for this work. To this aim, we used data from three different measurement stations located in the north-east of Spain, namely an urban background station (Barcelona, BCN), a regional background station (Montseny, MSY) and a mountaintop station (Montsec d'Ares, MSA). The median <span class="inline-formula"><i>C</i></span> 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 analysis of the cross-sensitivity to<span id="page6336"/> scattering, for the two filter tapes considered here, revealed a large increase in the <span class="inline-formula"><i>C</i></span> factor when the single-scattering albedo (SSA) of the collected particles was above a given threshold, up to a 3-fold increase above the average <span class="inline-formula"><i>C</i></span> values. The SSA threshold appeared to be site dependent and ranged between 0.90 to 0.95 for the stations considered in the study. The results of the cross-sensitivity to scattering displayed a fitted constant multiple-scattering parameter, <span class="inline-formula"><i>C</i><sub>f</sub></span>, of 2.21 and 1.96, and a cross-sensitivity factor, <span class="inline-formula"><i>m</i><sub>s</sub></span>, of 1.8 % and 3.4 % for the MSY and MSA stations, respectively, for the TFE-coated glass filter tape. For the M8060 filter tape, <span class="inline-formula"><i>C</i><sub>f</sub></span> values of 2.50, 1.96 and 1.82 and <span class="inline-formula"><i>m</i><sub>s</sub></span> values of 1.6 %, 3.0 % and 4.9 % for the BCN, MSY and MSA stations, respectively, were obtained. SSA variations also influenced the spectral dependence of <span class="inline-formula"><i>C</i></span>, which showed an increase with wavelength when SSA was above the site-dependent threshold. Below the SSA threshold, no statistically significant dependence of <span class="inline-formula"><i>C</i></span> on the wavelength was observed. For the measurement stations considered here, the wavelength dependence of <span class="inline-formula"><i>C</i></span> was to some extent driven by the presence of dust particles during Saharan dust outbreaks that had the potential to increase the SSA above the average values. At the mountaintop station, an omission of the wavelength dependence of the <span class="inline-formula"><i>C</i></span> factor led to an underestimation of the absorption Ångström exponent (AAE) by up to 12 %. Differences in the absorption coefficient determined from AE33 measurements at BCN, MSY and MSA of around 35 %–40 % can be expected when using the site-dependent experimentally obtained <span class="inline-formula"><i>C</i></span> value instead of the nominal <span class="inline-formula"><i>C</i></span> value. Due to the fundamental role that the SSA of the particles collected on the filter tape has in the multiple-scattering parameter <span class="inline-formula"><i>C</i></span>, we present a methodology that allows the recognition of the conditions upon which the use of a constant and wavelength-independent <span class="inline-formula"><i>C</i></span> is feasible.</p> |
| first_indexed | 2024-12-24T03:30:17Z |
| format | Article |
| id | doaj.art-591564199be64ceea325f91a5f31c632 |
| institution | Directory Open Access Journal |
| issn | 1867-1381 1867-8548 |
| language | English |
| last_indexed | 2024-12-24T03:30:17Z |
| publishDate | 2021-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Measurement Techniques |
| spelling | doaj.art-591564199be64ceea325f91a5f31c6322022-12-21T17:17:13ZengCopernicus PublicationsAtmospheric Measurement Techniques1867-13811867-85482021-10-01146335635510.5194/amt-14-6335-2021Determination of the multiple-scattering correction factor and its cross-sensitivity to scattering and wavelength dependence for different AE33 Aethalometer filter tapes: a multi-instrumental approachJ. Yus-Díez0J. Yus-Díez1V. Bernardoni2G. Močnik3G. Močnik4A. Alastuey5D. Ciniglia6M. Ivančič7X. Querol8N. Perez9C. Reche10M. Rigler11R. Vecchi12S. Valentini13M. Pandolfi14Institute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, SpainGrup de Meteorologia, Departament de Física Aplicada, Universitat de Barcelona, C/Martí i Franquès, 1, 08028, Barcelona, SpainDipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano & INFN Milano, via Celoria 16, 20133 Milan, ItalyCenter for Atmospheric Research, University of Nova Gorica, Vipavska 11c, 5270 Ajdovščina, SloveniaDepartment of Condensed Matter Physics, Jožef Stefan Institute, Jamova 39, 1000 Ljubljana, SloveniaInstitute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, SpainDipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano & INFN Milano, via Celoria 16, 20133 Milan, ItalyAerosol d.o.o., Kamniška 39A, 1000 Ljubljana, SloveniaInstitute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, SpainInstitute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, SpainInstitute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, SpainAerosol d.o.o., Kamniška 39A, 1000 Ljubljana, SloveniaDipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano & INFN Milano, via Celoria 16, 20133 Milan, ItalyDipartimento di Fisica “Aldo Pontremoli”, Università degli Studi di Milano & INFN Milano, via Celoria 16, 20133 Milan, ItalyInstitute of Environmental Assessment and Water Research (IDAEA), CSIC, C/Jordi Girona 18–26, 08034, Barcelona, Spain<p>Providing reliable observations of aerosol particles' absorption properties at spatial and temporal resolutions suited to climate models is of utter importance to better understand the effects that atmospheric particles have on climate. Nowadays, one of the instruments most widely used in international monitoring networks for in situ surface measurements of light absorption properties of atmospheric aerosol particles is the multi-wavelength dual-spot Aethalometer, AE33. The AE33 derives the absorption coefficients of aerosol particles at seven different wavelengths from the measurements of the optical attenuation of light through a filter where particles are continuously collected. An accurate determination of the absorption coefficients from the AE33 instrument relies on the quantification of the non-linear processes related to the sample collection on the filter. The multiple-scattering correction factor (<span class="inline-formula"><i>C</i></span>), which depends on the filter tape used and on the optical properties of the collected particles, is the parameter with both the greatest uncertainty and the greatest impact on the absorption coefficients derived from the AE33 measurements.</p> <p>Here we present an in-depth analysis of the AE33 multiple-scattering correction factor <span class="inline-formula"><i>C</i></span> and its wavelength dependence for two different and widely used filter tapes, namely the old, and most referenced, TFE-coated glass, or M8020, filter tape and the currently, and most widely used, M8060 filter tape. For performing this analysis, we compared the attenuation measurements from AE33 with the absorption coefficients measured with different filter-based techniques. On-line co-located multi-angle absorption photometer (MAAP) measurements and off-line PP_UniMI polar photometer measurements were employed as reference absorption measurements for this work. To this aim, we used data from three different measurement stations located in the north-east of Spain, namely an urban background station (Barcelona, BCN), a regional background station (Montseny, MSY) and a mountaintop station (Montsec d'Ares, MSA). The median <span class="inline-formula"><i>C</i></span> 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 analysis of the cross-sensitivity to<span id="page6336"/> scattering, for the two filter tapes considered here, revealed a large increase in the <span class="inline-formula"><i>C</i></span> factor when the single-scattering albedo (SSA) of the collected particles was above a given threshold, up to a 3-fold increase above the average <span class="inline-formula"><i>C</i></span> values. The SSA threshold appeared to be site dependent and ranged between 0.90 to 0.95 for the stations considered in the study. The results of the cross-sensitivity to scattering displayed a fitted constant multiple-scattering parameter, <span class="inline-formula"><i>C</i><sub>f</sub></span>, of 2.21 and 1.96, and a cross-sensitivity factor, <span class="inline-formula"><i>m</i><sub>s</sub></span>, of 1.8 % and 3.4 % for the MSY and MSA stations, respectively, for the TFE-coated glass filter tape. For the M8060 filter tape, <span class="inline-formula"><i>C</i><sub>f</sub></span> values of 2.50, 1.96 and 1.82 and <span class="inline-formula"><i>m</i><sub>s</sub></span> values of 1.6 %, 3.0 % and 4.9 % for the BCN, MSY and MSA stations, respectively, were obtained. SSA variations also influenced the spectral dependence of <span class="inline-formula"><i>C</i></span>, which showed an increase with wavelength when SSA was above the site-dependent threshold. Below the SSA threshold, no statistically significant dependence of <span class="inline-formula"><i>C</i></span> on the wavelength was observed. For the measurement stations considered here, the wavelength dependence of <span class="inline-formula"><i>C</i></span> was to some extent driven by the presence of dust particles during Saharan dust outbreaks that had the potential to increase the SSA above the average values. At the mountaintop station, an omission of the wavelength dependence of the <span class="inline-formula"><i>C</i></span> factor led to an underestimation of the absorption Ångström exponent (AAE) by up to 12 %. Differences in the absorption coefficient determined from AE33 measurements at BCN, MSY and MSA of around 35 %–40 % can be expected when using the site-dependent experimentally obtained <span class="inline-formula"><i>C</i></span> value instead of the nominal <span class="inline-formula"><i>C</i></span> value. Due to the fundamental role that the SSA of the particles collected on the filter tape has in the multiple-scattering parameter <span class="inline-formula"><i>C</i></span>, we present a methodology that allows the recognition of the conditions upon which the use of a constant and wavelength-independent <span class="inline-formula"><i>C</i></span> is feasible.</p>https://amt.copernicus.org/articles/14/6335/2021/amt-14-6335-2021.pdf |
| spellingShingle | J. Yus-Díez J. Yus-Díez V. Bernardoni G. Močnik G. Močnik A. Alastuey D. Ciniglia M. Ivančič X. Querol N. Perez C. Reche M. Rigler R. Vecchi S. Valentini M. Pandolfi 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 Atmospheric Measurement Techniques |
| title | 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 |
| title_full | 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 |
| title_fullStr | 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 |
| title_full_unstemmed | 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 |
| title_short | 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 |
| title_sort | 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 |
| url | https://amt.copernicus.org/articles/14/6335/2021/amt-14-6335-2021.pdf |
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