Droplet size increases with height from cloud base to cloud top. Droplets grow as they rise due to condensation when the environment has excess water vapor over the equilibrium value as in pseudoadiabatic ascent.
Condensation is the dominant growth process near the cloud base while droplets are small.
At higher levels within the cloud, where condensational growth has created a larger droplet, collision and coalescence becomes the dominant process in droplet growth. As droplets rise, they now begin to collide with other droplets and combine to form larger droplets. Droplet concentration increases with height for a few tens of meters above the cloud base, then decreases. For the first few tens of meters, CCN are still being activated within the cloud near the cloud base, therefore concentration increases. Once the point of maximum supersaturation is reached, the activation ceases and the concentration of cloud droplets formed by condensation reaches a steady state value.