S. Masuelli et al., GRAUPEL TRAJECTORIES AND CHARGING - A NEW NUMERICAL APPROACH FOR CLOUD ELECTRIFICATION STUDIES, Quarterly Journal of the Royal Meteorological Society, 124(548), 1998, pp. 1329-1341
In this work the growth, motion and charging of graupel particles are
simulated by computer. The cloud fields are calculated by a three-dime
nsional cloud model. Another program calculates the time evolution, in
side these cloud fields, of graupel properties (size, position, charge
and others). The electricity enters both in the charging of the parti
cles through their interactions with other particles and in the motion
itself, since in the equation of motion the electrical force is inclu
ded. Embryos with 500 mu m initial diameter are released at 656 locati
ons uniformly distributed in the updraught centre at four altitudes. T
he trajectories of all the particles are followed all the way to the 0
degrees C altitude. The graupel is charged by the ice-crystal-graupel
non-inductive mechanism. This kind of approach appears to be a powerf
ul tool to study the electric charging of the graupel in greater detai
l, since a very high spatial resolution (about 1 m) is easily achieved
. Some preliminary analysis of the charges on the precipitation partic
les is carried our and the results are related to in situ observations
. For the sake of comparison, trajectories without the electrical inte
raction are also computed, and it is shown that in some cases the fina
l radius with and without the electrical force can differ by a factor
of two to three in either direction depending on the initial position.