Impact of electro-collection and ice nucleation on aerosol scavenging

Abstract

The original two-moment aerosol scheme, which contains the prognostic equations for the number and mass of aerosol particles (APs), integrated into the ARPS numerical model, is used in this work. The electro-collection for cloud droplets is calculated with and without image charge, for raindrops only without image charge. A Boltzmann charge distribution on APs is assumed. It is assumed that the charge of the drops is proportional to the square of their diameter and can have both signs. The kernels calculated in discrete steps of APs and droplets/drops are incorporated into the bulk microphysical scheme of ARPS for the first time. The new, original expressions for the calculation of the scavenging coefficients for APs collected by cloud droplets and raindrops are contributed. Ice nucleation on APs is included as a nucleation scavenging mechanism. For the first time, the effects of the simultaneous action of these processes on the mass and number of APs in the air, as well as all hydrometeors and precipitation on the surface, are analyzed. Electrostatic collection for cloud droplets is the predominant collection mechanism, except for the smallest APs where Brownian diffusion dominates. When cloud droplets have more charge, more mass and a larger number of APs is scavenged. Even if the droplets are not charged, the collection effect is increased. Depositional nucleation scavenging is the most important mechanism of nucleation scavenging of APs, especially to reduce their mass. This approach and the results can be applied to air pollution problems, cloud modification and climate modeling.

Zahvalnica:

Istraživanje sprovedeno uz podršku Fonda za nauku Republike Srbije, br. 7389, Ekstremni vremenski događaji u Srbiji - analize, modeliranje i uticaji - EXTREMES