Cloud Particle Interactions-Collision, Coalescence, and Breakup

Abstract

In Chapter 10 we discussed the behavior of isolated cloud particles in some detail. Now we shall consider their hydrodynamic interactions, with a view to providing a quantitative assessment of the processes of particle growth by collision and coalescence, and of collisional breakup. We shall first treat the collision problem for drops of radii less than about 500μm which, in accordance with our previous description of drop distortion in Section 10.3.2, may be regarded as rigid spheres (at least when falling in isolation). This will be followed by a somewhat briefer discussion of the phenomena of drop coalescence and breakup. Finally, we shall consider water drop-ice crystal and ice crystal-ice crystal interactions, which lead to the formation of graupel, hail, and snow particles.