COLLISION RATE

The collision rate is the average rate at which water droplets collide in a cloud. It depends on the number of smaller droplets present and the size of the larger droplets relative to the smaller drops. The fall speed depends on the size of the drop. In order for collisions to occur there must be a dispersion in the drop sizes. Tiny drops will not collide with very large ones because they will be carried around them by the air flow. Collision between very large drops may lead to fragmentation. The growth rate of raindrops in a cloud depends on the collision rate.