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<p>An experimental setup to study aerosol hygroscopicity is proposed based on the temporal evolution of attenuated backscatter coefficients from a ceilometer colocated with an instrumented tower equipped with meteorological sensors at different heights. This setup is used to analyze a 4.5-year database at the ACTRIS SIRTA observatory in Palaiseau (Paris, France, 2.208<span class="inline-formula">^∘</span>&thinsp;E, 48.713<span class="inline-formula">^∘</span>&thinsp;N; 160&thinsp;m above sea level). A strict criterion-based procedure has been established to identify hygroscopic growth cases using ancillary information, such as online chemical composition, resulting in 8 hygroscopic growth cases from a total of 107 potential cases. For these eight cases, hygroscopic growth-related properties, such as the attenuated backscatter enhancement factor <span class="inline-formula"><i>f</i>_<i>β</i> (RH)</span> and the hygroscopic growth coefficient <span class="inline-formula"><i>γ</i></span>, are evaluated. This study shows that the hygroscopicity parameter <span class="inline-formula"><i>γ</i></span> is negatively correlated with the aerosol organic mass fraction but shows a positive correlation with the aerosol inorganic mass fraction. Among inorganic species, nitrate exhibited the highest correlation.</p> <p>This is the first time that hygroscopic enhancement factors are directly retrieved under ambient aerosols using remote-sensing techniques, which are combined with online chemical composition in situ measurements to evaluate the role of the different aerosol species in aerosol hygroscopicity.</p>