Modelled spongy growth and shedding process for spheroidal hailstones

Model calculations are carried out for spheroidal hailstone growth, by taking into account the results obtained by Garcı́a-Garcı́a and List from wind tunnel experiments. For the maximum hailstone diameter D varying from 2 to 4 cm, the liquid water contents at the onset of the wet growth and of shedding regimes (Wf,I and Wf,E, respectively) are represented as functions of both the air temperature Ta and D. The values of these parameters approach the experimental ones for D=2 cm, but show that, for D=4 cm, these transitions occur at 25% smaller values of Wf. Using the obtained parameterized equation of Wf,E, the dependence on Ta of the number of drops N(d) shed per km of fall by a particle of D=2 and 4 cm is studied for different values of Wf. For D=2 cm, it is shown that shedding is negligible at all temperatures for Wf<3 g m−3 and, even for Wf=4 g m−3 a value N(d) km−1=1000 is only reached near the melting level. According to these results, shedding from particles growing in the spongy regime would be much less pronounced than has been previously calculated. The effect of the variation of D on the shedding effect is also discussed.