Warm Cloud Precipitation

Let's begin by considering the case of a large droplet (r1) that falls through a uniform distribution of smaller droplets (r2). As the large droplet falls it experiencies a collision efficiency defined as However, a collision does not necessarly mean there is a coalescene of a small drop with the large droplet (called the collector droplet for obvious reasons). Hence there is also a coalescene efficiency which must be larger than 0 for the droplet to actually grow

Various lab measurements have been done to construct efficiency curves as a function of radius and ratio of collector drop size to the small droplet size. These are shown below: