Abstract
The growth rates of solid precipitation particles in a supercooled cloud were studied by numerical computations for the case when sublimation and the capture of cloud droplets take place simultaneously.
The principal conclusions obtained from the computations are as follows. (1) The necessary condition for the predominance of the capture-process in the growth of solid precipitation particles (in other words, the condition for the formation of graupel) is that the particle is initially a “frozen drop” with radius larger than a critical value, which is dependent mainly upon the initial height of the particle. (2) The relationship between the radii of graupel particles at cloud base and the height of the cloud top which was obtained from computations is in satisfactory agreement with that obtained from observations. (3) The computationally obtained probability that “frozen drops” of the critical size are formed due to the nucleation of supercooled water drops by their collision with ice crystals associated with atmospheric ice nuclei is about 10% of that expected from observations.
