Relative humidity impact on aerosol parameters in a Paris suburban area

[摘要] Measurements of relative humidity (RH) and aerosol parameters (scatteringcross section, size distributions and chemical composition), performed inambient atmospheric conditions, have been used to study the influence ofrelative humidity on aerosol properties. The data were acquired in asuburban area south of Paris, between 18 and 24 July 2000, in the frameworkof 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 overthe Paris area, the aerosol hygroscopicity is more or less pronounced. Theaerosol chemical composition data were used as input of a thermodynamicmodel to simulate the variation of the aerosol water mass content withambient RH and to determine the main inorganic salt compounds. The couplingof observations and modelling reveals the presence of deliquescenceprocesses with hysteresis phenomenon in the hygroscopic growth cycle. Basedon the Hänel model, parameterisations of the scattering crosssection, the modal radius of the accumulation mode of the sizedistribution and the aerosol water mass content, as a function of increasingRH, have been assessed. For the first time, a crosscheck of theseparameterisations has been performed and shows that the hygroscopicbehaviour of the accumulation mode can be coherently characterized bycombined optical, size distribution and chemical measurements.

[学科分类] 大气科学