MODELED 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 Garcia-Garcia and List fr om wind tunnel experiments. For the maximum hailstone diameter D varyi ng from 2 to 4 cm, the liquid water contents at the onset of the wet g rowth and of shedding regimes (W-f,W-I and W-f,W-E, respectively) are represented as functions of both the air temperature T-a and D. The va lues of these parameters approach the experimental ones for D = 2 cm, but show that, for D = 4 cm, these transitions occur at 25% smaller va lues of W-f. Using the obtained parameterized equation of W-f,W-E, the dependence on T-a 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 W-f. F or D = 2 cm, it is shown that shedding is negligible at all temperatur es for W-f < 3 g m(-3) and, even for W-f = 4 g m(-3) a value N(d) km(- 1) = 1000 is only reached near the melting level. According to these r esults, shedding from particles growing in the spongy regime would be much less pronounced than has been previously calculated. The effect o f the variation of D on the shedding effect is also discussed. (C) 199 8 Elsevier Science B.V. All rights reserved.