Topic #6: Moisture, Clouds and Precipitation Section #3: Cloud Types and Precipitation

 Clouds are the result of condensation of water droplets or ice crystals on dust in the atmosphere.  Clouds are classified on the basis of their form and height. Types of Clouds

 There are three types of clouds:  Cirrus clouds are high, white, and thin clouds.  Cumulus clouds are rounded individual cloud masses  Stratus clouds are sheets of clouds covering the sky Types of Clouds

 Clouds are also defined by the height at which they form.  High clouds are thin, white and often made up of ice crystals. They are not precipitation makers because there is little liquid water at high altitudes.  Middle clouds are found from about 2,000 to 6,000 meters and all have alto- as the prefix for their names.  Low clouds are clouds that form closest to the ground and are the clouds that most commonly bring rain and snow. Types of Clouds

 Fog is a cloud with its base at or very near the ground.  Fog can form due to a cooling of air which causes a quick condensation of the water in the air.  Fog can also when air heats up over water and causes a quick evaporation of water. Fog

 For precipitation to form cloud droplets must reach saturation in the atmosphere, this is usually equal to a roughly 1,000,000 times increase in volume.  Precipitationis any form of water which condenses and falls from the sky. How Precipitation Forms

 Snow forms by the Bergeron process which is the supercooling and supercondensing of water droplets in a cloud.  Water does not freeze at 0 ̊C as you would expect, it freezes at -40 ̊C and this is called supercooling (water in liquid state below 0 ̊C.  Since ice is more dense than liquid water the atmosphere can hold more of it so when the atmosphere is saturated with ice it is said to be supersaturated. How Precipitation Forms

 Rain is formed in warm clouds by the collision- coalescence process.  As water condenses on a condensation nuclei it will begin to fall and collide with other water droplets causing them to coalesce (combine) to form larger water droplets. How Precipitation Forms