A laboratory study of the effect of velocity on Hallett–Mossop ice crystal multiplication

Abstract

Laboratory experiments into the effect of ice multiplication in clouds by the Hallett–Mossop (H–M) mechanism have been extended to higher velocities than in earlier studies. The secondary ice particle production rate per milligram of rime accreted is found to be dependent on the velocity of the graupel pellet as it accretes supercooled droplets. In the range 1.5 to 12 m s −1, the maximum secondary ice particle ejection occurs at 6 m s −1 with a rate of one crystal per 70 mg of accreted rime. The relevance of these new results to the particle production mechanism and to behaviour in natural clouds is discussed.