Abstract
Abstract. 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∘ E, 48.713∘ N; 160 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 fβ (RH) and the hygroscopic growth coefficient γ, are evaluated. This study shows that the hygroscopicity parameter γ 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. 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.
Highlights
The role of natural and anthropogenic aerosol particles and greenhouse gases in the climate system has been deeply studied to evaluate the radiative forcing effect on the Earth’s surface temperature (Twomey, 1977; Albrecht, 1989)
Bedoya Velásquez et al.: Long-term aerosol optical hygroscopicity study aerosol–radiation interaction (ARI), which produces a direct effect on the Earth’s radiative fluxes mainly by scattering and absorbing radiation, and (ii) the aerosol–cloud interaction (ACI) associated with changes in cloud properties and precipitation given that particles can act as cloud condensation nuclei (CCN) and ice nuclei (IN) (Boucher et al, 2013)
Once a simultaneous monotonic decrease was observed for β and RH/100 −γ fξ (RH) in cases 3 and 8, we applied the Hänel parameterization, obtaining the corresponding γ and fβ (RH = 85 %)
Summary
The role of natural and anthropogenic aerosol particles and greenhouse gases in the climate system has been deeply studied to evaluate the radiative forcing effect on the Earth’s surface temperature (Twomey, 1977; Albrecht, 1989). Bedoya Velásquez et al.: Long-term aerosol optical hygroscopicity study aerosol–radiation interaction (ARI), which produces a direct effect on the Earth’s radiative fluxes mainly by scattering and absorbing radiation, and (ii) the aerosol–cloud interaction (ACI) associated with changes in cloud properties and precipitation given that particles can act as cloud condensation nuclei (CCN) and ice nuclei (IN) (Boucher et al, 2013). Both interactions result in a net radiative effect on the global energy budget
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