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Original title:
WATER TO RULE THEM ALL: A MEASUREMENT OF THE HYGROSCOPIC LIGHT SCATTERING ENHANCEMENT USING A NOVEL SINGLE-NEPHELOMETER SETUP SYSTEM AT URBAN BACKGROUND SITE
Authors: Suchánková, Lenka ; Ondráček, J. ; Zíková, N. ; Roztočil, P. ; Vodička, P. ; Prokeš, Roman ; Holoubek, Ivan ; Ždímal, V.
Document type: Papers
Conference/Event: Výroční konference České aerosolové společnosti OVZDUŠÍ V ČASe /24./, Hustopeče (CZ), 20251110
Year: 2025
Language: eng
Abstract: International monitoring programmes recommend measuring aerosol optical properties at relative humidities (RH) below 40% to ensure comparability between atmospheric stations worldwide (WMO/GAW, 2016). However, aerosol hygroscopicity — the ability of particles to take up and retain water vapor — significantly alters their physical, chemical, and optical properties, thereby influencing their climate impacts (Burgos et al., 2019, Zieger et al., 2015). The light scattering enhancement factor, f(RH > 80%), quantifies the increase in aerosol scattering under humidified conditions relative to dry conditions (Titos et al., 2021). METHODOLOGY In this study, we introduce a novel single-nephelometer setup designed to reduce measurement uncertainty and reliably detect changes in aerosol light backscattering under elevated RH, f(RH > 80%)bsp. Ambient aerosols were sampled through a PM₁₀ inlet, dried (<40% RH), and split into two streams: one remained dry, while the other was humidified (>80% RH) using a Nafion membrane. The Integrating Nephelometer TSI 3563 alternately measured dry and humidified samples every 60 min to obtain total and backscattering coefficients at three wavelengths. The system was deployed at the ACTRIS urban background site in Prague (50°07′N, 14°23′E) from November 2022 to August 2023. The derived f(RH > 80%) and f(RH > 80%)bsp values were analyzed together with meteorological parameters, estimated chemical composition, particle number size distributions (PNSD), air mass back trajectories, and new particle formation (NPF) events to assess hygroscopic behavior in an urban European environment. RESULTS, DISCUSSION, CONCLUSIONS Both f(RH > 80%) and f(RH > 80%)bsp exhibited some of the lowest values reported in the literature, indicating modest hygroscopic growth of aerosol light scattering at the site. Water uptake by particles increased the single scattering albedo (SSA, Fig. 1B), reflecting enhanced total light scattering. Conversely, a decrease in the backscattering fraction (b, Fig. 1A) with increasing RH suggested stronger forward scattering due to particle growth. Both effects are critical for accurate estimation of the aerosol direct radiative effect. The weak hygroscopic response was attributed to a dominant carbonaceous aerosol mixture, primarily black (BC) and brown (BrC) carbon, with occasional dust or marine aerosol influence. Both f(RH > 80%) and f(RH > 80%)bsp were positively correlated with the ratio of secondary organic carbon (SOC) to total OC. Principal component (PCA) and PNSD analyses revealed the relative contribution of NPF to the observed hygroscopic scattering enhancement. In conclusion, the single-nephelometer system was proven to reliably quantify RH-dependent changes in aerosol light scattering in the ambient atmosphere. Its main limitations were the reduced temporal resolution and the absence of simultaneous dry/humidified measurements, restricting its use for detailed humidogram analyses.
Keywords: aerosol climate effects; aerosol optical properties; hygroscopicity
Project no.: LM2023030 (CEP), LM2023048 (CEP), EH22_008/0004635
Funding provider: GA MŠk, GA MŠk, GA MŠk
Host item entry: SBORNÍK XXIV. výroční konference České aerosolové společnosti OVZDUŠÍ V ČASe, ISBN 978-80-908653-3-4
Note: Související webová stránka: https://cas.icpf.cas.cz/download.php
Institution: Global Change Research Institute AS ČR (web)
Document availability information: Fulltext is available in the digital repository of the Academy of Sciences.
Original record: https://hdl.handle.net/11104/0376974
Permalink: http://www.nusl.cz/ntk/nusl-697190
The record appears in these collections:
Research > Institutes ASCR > Global Change Research Institute
Conference materials > Papers
Authors: Suchánková, Lenka ; Ondráček, J. ; Zíková, N. ; Roztočil, P. ; Vodička, P. ; Prokeš, Roman ; Holoubek, Ivan ; Ždímal, V.
Document type: Papers
Conference/Event: Výroční konference České aerosolové společnosti OVZDUŠÍ V ČASe /24./, Hustopeče (CZ), 20251110
Year: 2025
Language: eng
Abstract: International monitoring programmes recommend measuring aerosol optical properties at relative humidities (RH) below 40% to ensure comparability between atmospheric stations worldwide (WMO/GAW, 2016). However, aerosol hygroscopicity — the ability of particles to take up and retain water vapor — significantly alters their physical, chemical, and optical properties, thereby influencing their climate impacts (Burgos et al., 2019, Zieger et al., 2015). The light scattering enhancement factor, f(RH > 80%), quantifies the increase in aerosol scattering under humidified conditions relative to dry conditions (Titos et al., 2021). METHODOLOGY In this study, we introduce a novel single-nephelometer setup designed to reduce measurement uncertainty and reliably detect changes in aerosol light backscattering under elevated RH, f(RH > 80%)bsp. Ambient aerosols were sampled through a PM₁₀ inlet, dried (<40% RH), and split into two streams: one remained dry, while the other was humidified (>80% RH) using a Nafion membrane. The Integrating Nephelometer TSI 3563 alternately measured dry and humidified samples every 60 min to obtain total and backscattering coefficients at three wavelengths. The system was deployed at the ACTRIS urban background site in Prague (50°07′N, 14°23′E) from November 2022 to August 2023. The derived f(RH > 80%) and f(RH > 80%)bsp values were analyzed together with meteorological parameters, estimated chemical composition, particle number size distributions (PNSD), air mass back trajectories, and new particle formation (NPF) events to assess hygroscopic behavior in an urban European environment. RESULTS, DISCUSSION, CONCLUSIONS Both f(RH > 80%) and f(RH > 80%)bsp exhibited some of the lowest values reported in the literature, indicating modest hygroscopic growth of aerosol light scattering at the site. Water uptake by particles increased the single scattering albedo (SSA, Fig. 1B), reflecting enhanced total light scattering. Conversely, a decrease in the backscattering fraction (b, Fig. 1A) with increasing RH suggested stronger forward scattering due to particle growth. Both effects are critical for accurate estimation of the aerosol direct radiative effect. The weak hygroscopic response was attributed to a dominant carbonaceous aerosol mixture, primarily black (BC) and brown (BrC) carbon, with occasional dust or marine aerosol influence. Both f(RH > 80%) and f(RH > 80%)bsp were positively correlated with the ratio of secondary organic carbon (SOC) to total OC. Principal component (PCA) and PNSD analyses revealed the relative contribution of NPF to the observed hygroscopic scattering enhancement. In conclusion, the single-nephelometer system was proven to reliably quantify RH-dependent changes in aerosol light scattering in the ambient atmosphere. Its main limitations were the reduced temporal resolution and the absence of simultaneous dry/humidified measurements, restricting its use for detailed humidogram analyses.
Keywords: aerosol climate effects; aerosol optical properties; hygroscopicity
Project no.: LM2023030 (CEP), LM2023048 (CEP), EH22_008/0004635
Funding provider: GA MŠk, GA MŠk, GA MŠk
Host item entry: SBORNÍK XXIV. výroční konference České aerosolové společnosti OVZDUŠÍ V ČASe, ISBN 978-80-908653-3-4
Note: Související webová stránka: https://cas.icpf.cas.cz/download.php
Institution: Global Change Research Institute AS ČR (web)
Document availability information: Fulltext is available in the digital repository of the Academy of Sciences.
Original record: https://hdl.handle.net/11104/0376974
Permalink: http://www.nusl.cz/ntk/nusl-697190
The record appears in these collections:
Research > Institutes ASCR > Global Change Research Institute
Conference materials > Papers
Record created 2026-03-22, last modified 2026-03-22