Alessandro Facinetto

Being naturally present in the atmosphere as volcanic or desert dusts, produced by living organisms or by human activities, aerosols can interact both directly and indirectly with the atmosphere’s radiation budget. Aerosols can scatter sunlight back into space (direct effect), or trigger the formation of clouds effectively changing the atmosphere’s energy budget (indirect effect). Among other pollutants, jet aircraft engines release in the high troposphere soot aerosols that may act as ice/condensation nuclei for the heterogeneous nucleation of ice and supercooled water. The resulting condensation trails (contrails) may persist and even evolve to cirrus-like clouds when the thermodynamic conditions are favorable, especially in high density air traffic regions. In order to better understand the indirect role of atmospheric aerosols and especially soot on cloud formation, a dedicated
experiment, the Lille ice nucleation chamber (LINC), is being implemented by PC2A research group in CERLA laboratories. LINC is a continuous flow diffusion chamber based on the system developed at the Colorado State University (CDU-CFDC) and more recently improved at the Swiss Federal Institute of Technology in Zurich (ZINC) . LINC allows recreating a low-temperature environment at controlled ice/water supersaturation where the aerosols are injected. The heterogeneous nucleation rates are then investigated as a function of physical and chemical properties of the aerosols, like their size distribution and surface chemical composition. The experimental data are expected to provide useful information on the heterogeneous processes involved in the ice/water nucleation and to validate theoretical models representative of the heterogeneous nucleation dynamic in the high troposphere.

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