Relative humidity impact on aerosol parameters in a Paris suburban area H. Randriamiarisoa1, P. Chazette1, P. Couvert1,†, J. Sanak1, and G. Mégie2,†† 1Laboratoire des Sciences du Climat et de l’Environnement/Institut Pierre-Simon Laplace, Orme des Merisiers Bât 701, C.E.Saclay, 91191 Gif-sur-Yvette Cedex, France 2Service d’Aéronomie/Institut Pierre-Simon Laplace, 4 place Jussieu, 75252 Paris, France †deceased, June 2005 ††deceased, June 2004
Abstract. Measurements of relative humidity (RH) and aerosol parameters (scattering
cross section, size distributions and chemical composition), performed in
ambient atmospheric conditions, have been used to study the influence of
relative humidity on aerosol properties. The data were acquired in a
suburban area south of Paris, between 18 and 24 July 2000, in the framework
of the "Etude et Simulation de la Qualité de l'air en Ile-de-France"
(ESQUIF) program. According to the origin of the air masses arriving over
the Paris area, the aerosol hygroscopicity is more or less pronounced. The
aerosol chemical composition data were used as input of a thermodynamic
model to simulate the variation of the aerosol water mass content with
ambient RH and to determine the main inorganic salt compounds. The coupling
of observations and modelling reveals the presence of deliquescence
processes with hysteresis phenomenon in the hygroscopic growth cycle. Based
on the Hänel model, parameterisations of the scattering cross
section, the modal radius of the accumulation mode of the size
distribution and the aerosol water mass content, as a function of increasing
RH, have been assessed. For the first time, a crosscheck of these
parameterisations has been performed and shows that the hygroscopic
behaviour of the accumulation mode can be coherently characterized by
combined optical, size distribution and chemical measurements.
Citation: Randriamiarisoa, H., Chazette, P., Couvert, P., Sanak, J., and Mégie, G.: Relative humidity impact on aerosol parameters in a Paris suburban area, Atmos. Chem. Phys., 6, 1389-1407, doi:10.5194/acp-6-1389-2006, 2006.