A three-dimensional numerical study to evaluate the electrification ca
used by only the ice crystal-graupel collisions mechanism is presented
. The electrification model includes the dependencies of the magnitude
of the separated charge with the crystal size and the relative veloci
ty. In addition, the dependence of the reversal temperature (T-r) with
the liquid water content is taken into account following two differen
t experimental data sets: Takahashi [1978] and Saunders et al. [1991].
The particle spectrum is discrete with eight categories. The results
show that using the first data set, the tripolar structure is obtained
producing magnitudes of the charge densities in accordance with in si
tu measurements, whereas using the second data set, an inverted dipole
(negative on positive) is obtained. Possible causes for these discrep
ancies are discussed. Also, the charge on individual particles is disc
ussed in the frame of experimental, data reported by airborne in situ
measurements.