Cloud Types & Precipitation Chapter 18.3 Cloud Types & Precipitation Who is Stan Hatfield and Ken Pinzke

What is a cloud? A cloud is a visible group of tiny water droplets or ice crystals in the air. YouTube: Strange Cloud Formations

3 CONDITIONS ARE NECESSARY FOR CLOUDS TO FORM. The air temperature must be lowered to the dew point. (Air is saturated) A solid surface must be available for condensation to occur. (condensation nuclei) Low pressure

Clouds are classified by form (shape) height

4 BASIC FORMS (Shapes) OF CLOUDS Cirrus – wispy, feathery Cumulus – piled, fluffy Stratus – layered Nimbus - rain

3 Levels of Cloud Height Height is determined by where the base of the cloud is High (above 6000m) Middle (2000m – 6000m) Low (below 2000m) Base

HIGH CLOUDS All high altitude clouds are made of ice crystals due to the cold air in the upper sky. Group consists of Cirrus Cirrostratus Cirrocumulus

Cirrus Clouds

Cirrostratus Clouds

Cirrocumulus Clouds

Middle Clouds Middle clouds are made of ice crystals and water droplets. Group consists of Altocumulus Altostratus

Altocumulus

Altostratus

Low Clouds Low clouds consist of water droplets. Group consists of Cumulus Stratus Stratocumulus Nimbostratus (rain cloud)

Cumulus

Stratus

Stratocumulus

Nimbostratus

Cumulonimbus Clouds (Thunder Clouds) build up from low altitudes to elevations over 6000m associated with: lightning & thunder Hail Tornadoes heavy rain

Contrails

Cloud Classification Makes no sense without caption in book

18.3 Cloud Types and Precipitation Fog 18.3 Cloud Types and Precipitation  Fog is defined as a cloud with its base at the ground.  Fog Caused by: • As the air cools, it becomes denser and drains into low areas such as river valleys, where thick fog accumulations may occur. • When cool air moves over warm water, enough moisture may evaporate from the water surface to produce saturation.

Precipitation Any liquid or solid particle that falls from a cloud

What is Collision-coalescence? Water droplets within a cloud crash into each other and get bigger and bigger until they fall from the cloud.

Starts as snow falling from clouds Melts on its way down Rain Starts as snow falling from clouds Melts on its way down Reaches ground as liquid Dry air: rain drop may evaporate before hitting the ground

Ice falling from clouds Size & shape depend on how cold it is Snow Ice falling from clouds Size & shape depend on how cold it is Temperature must be below freezing during journey Dry air: small crispy snowflakes Wet air: large wet snowflakes (great for making snowballs)

Sleet Ice falling from clouds Layer of warm air melts to rain Then refreezes again in cold air above the ground

Freezing Rain Ice falling from clouds Layer of warm air melts to rain The ground is below freezing Rain hits the ground and freezes on contact

Hail Balls of ice that fall from a cumulonimbus cloud Only during a thunderstorm Ice gets swept up and down in updrafts They grow larger as water refreezes each time they rise.

Largest Recorded Hailstone Makes no sense without caption in book