Aerosols lead to cloud formation (cloud droplets, ice crystals) and affect cloud properties (microphysical, lifetime, precipitation). Their effect on the microphysics and radiative cloud properties (referenced as first indirect effect, 1st AIE) is poorly characterized and their impact on precipitation (referenced as second indirect effect, 2nd AIE) is even less well understood. The questions that we are adressing concern the links between aerosol (characteristics (morphology, chemical composition) and hygroscopic properties as well as the mechanisms involved in contrails and clouds formation.
Among the aerosol types, it is known that anthropogenic aerosols produced by aircraft traffic may modify the global and regional cloud amounts and contribute to radiative forcing. If the thermodynamic conditions necessary for the appearance of the cirrus-like trails of condensed vapor (contrails) are relatively well understood, their microphysical properties and finally their impact on radiation budget and on climate are currently under investigation. Similarly, less is known on the specific contribution of natural bio-aerosols to cloud formation and precipitation through their effects on cloud droplet and ice crystal initiation. The potentially high numbers of bio-aerosols in the low levels of the atmosphere their wide distribution over vegetative surfaces and oceans, and their likely strong seasonal and climatic variability make it important for more focused studies.
Materials and methods
Laboratory equipement
Laser desorption / Laser ionization / Mass Spectrometry (L2MS)
Secondary Ion Mass Spectrometry (SIMS, Lille 1 University Platform)
Ice and Droplet Nucleation Experimental Set-up (IDRONES)
Instrumentations dedicated to remote sensing observations
Micro-lidar (at 532 nm)
Multi- wavelength infrared radiometer
Multi-wavelength LIDAR (LILAS)
Satellite data
PARASOL
CALIPSO
MODIS
Ongoing studies and results
Instrumental development in order to increase the selectivity and sensitivity of the analysis of the surface chemical composition of soot: home-made VUV (10.5 eV) ionization source
Instrumental development : LINC (Lille Ice Nucleation Chamber) experimental facility to reproduce at the laboratory scale the heterogeneous nucleation of ice/water in conditions that mimic those of the high troposphere.
Sensitivity analysis of the impact of the composition of the crystals (air bubbles, soot) on their optical properties in the solar field and in polarization.
Study of aerosol hygroscopicity in condensation mode by means of a hygrometer coupled with a temperature-controlled reactor cell.
Study of the soot formation process: in situ measurement in flames. Highlighting of the smallest incandescent particles. Establishment of soot threshold index (TSI).
Chemical composition of pollen grains analyzed by micro-Raman and infrared spectroscopy. Insight on the nucleation activities of the bio-aerosols and their released materials.
Detection and characterization of natural cirrus clouds and aircraft contrails over Lille : statistical analysis over the period 2008-2013 of macro-physical and radiative properties (base and top altitudes, geometric thickness, optical thickness, extinction coefficient, lidar ratio). Possibility of establishing a method for detecting natural cirrus clouds and aircraft contrails and their discrimination from the ground (LILAS) and from space (CALIPSO)
Study of the activated fraction of soot particles (ratio of the number of droplets formed/number of seeding particles) vs. water supersaturation. Impact of the nature of soot (i.e. influence of fuel: diesel, kerosene …), morphology on the activated fraction – Development of an experimental protocol to determine the activity of aerosols as ice nuclei (IN) in immersion mode.
Illustration : (Left) The Lille Ice Nucleation Chamber (LINC). The 10 mm large nucleation chamber is visible in the lower section. (Right) Example of a Generated flame in laboratory
Key publications
P. Parent, C. Laffon, I. Marhaba, D. Ferry, T.Z. Regier, I.K. Ortega, B. Chazallon, Y. Carpentier, C. Focsa, “Nanoscale characterization of aircraft soot: a high-resolution transmission electron microscopy, Raman spectroscopy, X-ray photoelectron and near-edge X-ray absorption spectroscopy study”, Carbon 101, 86-100 (2016)
A.Faccinetto, C. Focsa, P. Desgroux, M. Ziskind, “Progress toward the Quantitative Analysis of PAHs Adsorbed on Soot by Laser Desorption/Laser Ionization/Time-of-Flight Mass Spectrometry”, Environ. Sci. Technol. 49, 10510-10520 (2015)
Laser induced incandescence technique to identify soot nucleation and very small particles in low-pressure methane flames. Applied Physics B, Volume 112, Issue: 3, 369-379, 2013£ MOUTON T., MERCIER X., WARTEL M., LAMOUREUX N., DESGROUX P.
Laser induced fluorescence spectroscopy of aromatic species produced in atmospheric sooting flames using UV and visible excitation wavelengths Combustion and Flame; Vol.161, pp. 2479–2491, 2014 Bejaoui S., Mercier X., Desgroux P., Therssen E.
Probing the smallest soot particles in low-sooting premixed flames using laser-induced Incandescence Proceedings of the Combustion Institute, Vol.35; 2015, pp. 1843–1850, 2015 Bladh H., Olofsson N.E, Mouton T, Simonsson J., Mercier X., Faccinetto A., Bengtsson P.E, Desgroux P.
Measurements and Modeling of Laser-Induced Incandescence of Soot at Different Heights in a Flat Premixed Flame. Appl. Phys. B118 (3), pp. 449-469, 2015 Bejaoui S., Batut S., Therssen E., Lamoureux N., Desgroux P., Liu F.
Experimental and numerical study on rich methane/hydrogen/air laminar premixed flames at atmospheric pressure: Effect of hydrogen addition to fuel on soot gaseous precursors Int. J. of Hydrogen, submitted Mze Ahmed A., Mancarella S., Desgroux P., Gasnot L., Pauwels J.F., El Bakali A.
Isomer discrimination of PAHs formed in sooting flames by jet cooled laser induced fluorescence: Application to the measurement of pyrene and fluoranthene Applied Physics B, in press Mouton T., Mercier X., Desgroux P.
