Precipitation From Condensation in Clouds:
1. The Bergeron Process
2. The Collision-Coalescence Process
The Bergeron Process: Condensation at Temperatures Below Freezing
Droplets Begin to Combine:
- Water vapor molecules become a part of ice crystals.
- When ice crystals become large enough, they fall.
- Temperatures at lower altitudes are warmer; therefore ice crystals may melt into raindrops.
- A large droplet runs into smaller droplet
- The two combine into one larger droplet
- The coalescence(combining) of droplets can only take place if the droplets have opposite electrical charges. If the droplets have the same charge they will bounce off of each other.
The Collision-Coalescence Process: Condensation at Temperatures Above Freezing
- This usually occurs near the tropics where the air is warm and their are few condensation nuclei
- Precipitation droplets are removed from the air by condensation nuclei
- Droplets must be at least 0.02 millimeters in order to precipitate
As droplets get bigger they...
- absorb even more small droplets
- pick up speed
- Once at a size of about 4 millimeters, the surface tension of the droplet is overcome by the air friction of falling and it breaks up
Collision-Coalescence Process
Rain storm!