A numerical study of the effects of the aerosol particle spectrum on the development of the ice phase and precipitation formation

The aim of this work is to study the influence of pollution here considered in terms of the initial aerosol particle spectrum on the development of the ice phase and its contribution to precipitation formation. Therefore, we use a 1D1/2 detailed microphysics model and conduct a number of sensitivity studies of the 19th July 1981 CCOPE case, whose main microphysical characteristic was the formation of precipitation entirely via the ice phase. After a review of the importance of the ice phase and the impact of pollution on precipitation formation, the model is described. Then we present the CCOPE case and compare the results of the model with the observations of the airplanes. Finally, we use different aerosol particle spectra to initiate the microphysics and examine the impacts on both dynamics and precipitation formation mechanisms. The relative importance of the secondary ice production mechanism (rime-splintering) with respect to other ice processes is addressed. Some sensitivity studies are also made concerning the importance of the chemical characteristics of the aerosol particles and their impact on precipitation formation. Furthermore, the precipitation is compared with and without the ice phase as a function of pollution. The results show that rain accumulation at the ground is strongly dependent on the total number of aerosol particles present at the beginning of the simulation and also on their solubility. This effect is even more pronounced when rain formation proceeds via mixed-phase processes as compared to only warm-rain processes.