gravity and frictional drag create a balance called terminal velocity. a falling object no longer has an acceleration because gravity is balanced by friction. so in order for a rain drop to fall and overcome terminal velocity it must be kinda large.
Collision-Coalescense Process
generates precipitation. begins with large droplets with high terminal velocities. the collector droplets collide with smaller droplets. compressed air forces the smaller droplets outside. and the collector drops capture the larger cloud drops.
Coalescence Efficiency
tends to be very high because most of the droplets are coalessed into the collector drop and are unable to escape.
Bergeron Process
saturation vapor pressure of ice is less than super cooled water. when both are present, the super cooled water will be deposited onto the ice because the ice has a lower pressure causing the ice crystals to grow rapidly. the falling of the ice crystals and water creates riming and aggregation.
Riming
when ice crystals fall through a cloud and collide with supercooled droplets, the liquid water freezes onto them.
Aggregation
the joining of two ice crystals to form a single larger ice crystal.
Snow
results from the burgeron process, riming and aggregation.
Rain
always associated with warm clouds.
Graupel
ice crystals that undergo extensive riming. falls to ground or provides nucleus for hail
Hail
concentric layers of ice build around graupel. repeated process of graupel being forced back up by updrafts and more ice forming around it. great plains has the highest frequency of hail events.
Sleet
begins as ice crystals which melt
into rain through a mid-level inversion before solidifying in colder, near
surface air
Freezing Rain
similar to sleet but the drops do not sollidify before hitting the surface.