Observational Evidence for Relative Humidity Driving Black Carbon Mixing State and Absorption Enhancement in Urban Outflows

Abstract Black carbon (BC)‐containing particles are the most strongly absorbing component of atmospheric aerosol, contributing to global warming. Quantifying their radiative effects remains challenging because BC absorption depends on their mixing state which can evolve through atmospheric aging. This study presents unique direct aircraft observations of BC absorption enhancement and mixing state in urban outflows from Paris. We show that the absorption of BC either increases or remains unchanged during plume transport at the regional scale. By using an unsupervised machine learning approach, we identify clusters of BC properties associated with specific meteorological conditions and chemical composition. The analysis reveals that relative humidity (RH) significantly influences BC absorption enhancement. We derive a time‐dependent rate of 0.20 hr −1 for BC absorption enhancement at RH above 60%, decreasing the rate to less than half in drier conditions. These findings emphasize the need to include RH‐dependent parametrizations to improve estimates of BC radiative effects.

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Publication Details

Journal
Geophysical Research Letters
Published
2026-04-14
DOI
https://doi.org/10.1029/2025gl121520
Primary Topic
Atmospheric chemistry and aerosols
Type
article
Field-Weighted Citation Impact
0.00

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article

Observational Evidence for Relative Humidity Driving Black Carbon Mixing State and Absorption Enhancement in Urban Outflows

Ludovico Di Antonio, A. Bauville, Alejandra Velazquez-Garcia, F. Burnet et al.
Geophysical Research Letters
Atmospheric chemistry and aerosols
article

Observational Evidence for Relative Humidity Driving Black Carbon Mixing State and Absorption Enhancement in Urban Outflows

Ludovico Di Antonio, A. Bauville, Alejandra Velazquez-Garcia, F. Burnet, T. Bourrianne, Paola Formenti, P. F. DeCarlo, Cyrielle Denjean, C. Yu, G. Siour, D.L. Pereira, C. Cantrell, B. A. Nault, K. Tu, M. Cazaunau, S. Tinorua, E. Pangui, M. Beekmann, V. Michoud
article en

Abstract

Abstract Black carbon (BC)‐containing particles are the most strongly absorbing component of atmospheric aerosol, contributing to global warming. Quantifying their radiative effects remains challenging because BC absorption depends on their mixing state which can evolve through atmospheric aging. This study presents unique direct aircraft observations of BC absorption enhancement and mixing state in urban outflows from Paris. We show that the absorption of BC either increases or remains unchanged during plume transport at the regional scale. By using an unsupervised machine learning approach, we identify clusters of BC properties associated with specific meteorological conditions and chemical composition. The analysis reveals that relative humidity (RH) significantly influences BC absorption enhancement. We derive a time‐dependent rate of 0.20 hr −1 for BC absorption enhancement at RH above 60%, decreasing the rate to less than half in drier conditions. These findings emphasize the need to include RH‐dependent parametrizations to improve estimates of BC radiative effects.

Geophysical Research LettersVol. 53(8)
Centre National de la Recherche Scientifique (FR), University of Helsinki (FI), Johns Hopkins University (US), Université de Versailles Saint-Quentin-en-Yvelines (FR), Université Paris-Est Créteil (FR), Université Paris Cité (FR), Helsinki Institute of Physics (FI), Paris-Est Sup (FR), Paul Scherrer Institute (CH), Sorbonne Université (FR), Finland University (FI), Aerodyne Research (US), Météo-France (FR), Institut Pierre-Simon Laplace (FR), Muséum national d'Histoire naturelle (FR), Laboratoire Interuniversitaire des Systèmes Atmosphériques (FR), Laboratoire atmosphères, milieux, observations spatiales (FR), Laboratoire Techniques, Territoires et Sociétés (FR), Saft (France) (FR)
Centre National de la Recherche Scientifique, HORIZON EUROPE Marie Sklodowska-Curie Actions
Sustainable cities and communities
Openalex Percentile: Top 16%
Atmospheric chemistry and aerosols
DOIOpen Access PDFOpenAlex
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