Clouds and Precipitation

By: Jeanette Rivera

Adiabatic Temperature changes and Expansion cooling

• Heat not added or subtracted when temperature changes

• Traveling up earths surface atmospheric pressure decreases because of fewer gas molecules

• Dry adiabatic rate- rate of cooling and heating applied to unsaturated air.

• Wet adiabatic rate- slower when cooling cause by latent heat.

Orographic Lifting

• Elevated terrains acting as barriers to air flow making orographic lifting occur.

• Orographic air- lifts air• Most moisture is lost by the time air reaches

leeward side of a mountain

Frontal wedging

• Warm air and cool air collide producing a front• In North America cooler denser makes

warmer less dense air rise.• Warm is rising the cool air is toward the

bottom forming rain

Convergence

• Air in the lower atmosphere flowing together makes the air go up which is called convergence

• Pattern of air movement and uplifting is accompanied by solar heat

• Florida experiences great amount of mid afternoon thunderstorms

Localized Convective Lifting

• Pockets of air may occur due to unequal heating on summer days

• Rising parcel of warm air called thermals• Clouds form when warm parcel air rises above

condensation

Stability

• Volume air rise- temperature decreases do to expansion

• Volume air cooler- environment ,more denser• Stable air- resists vertical air

Condensation

• Occurs when water vapor liquid• Water vapor liquid can be in the form of

dew, fog, or clouds• Air must be saturated before any of the forms

of condensation occur

Types of cloud

• Cirrus and cumulus• Cirrus- white, thin, high clouds• Cumulus- rounded individual cloud masses.• Stratus- a cloud with layers that cover much of

the sky

High Clouds

• Cirrus, Cirrostratus, and cirrocumulus make up a high cloud

• White, thin and often made up of ice crystals• May leave a warn of stormy weather

approaching

Middle Clouds

• In the middle and alto is part of their name• Is an altocumulus cloud which is denser and

larger• Light snow or drizzle is infrequent

Low Clouds• Stratus, Stratocumulus, and nimbostratus are

all apart of the low cloud• May produce light precipitation• More towards the bottom and weather occurs

more

Clouds of Vertical Development

• Clouds are more lower but stretch to higher or middle altitude

• Associate with unstable air• Cumulonimbus cloud may produce rain

showers or thunderstorms

Fog

• Fog formation- when earth surface cool rapidly on cool, calm, clear nights

• Air more denser, making thick fog occur• Cool air evaporates over warm water

producing saturation• Same structure and shape as a cloud

Cold Cloud Precipitation

• Cold air does not freeze at 0*C.• Water in liquid state at 0 degrees Celsius is

called super cooled• Ice crystals cant coexist with water droplets in

air due to super saturation on ice crystals

Warm Cloud Precipitation

• Warm clouds- mechanism forming water droplets in collision-coalescence process

• Salt able to remove water vapor from the air at relative humidities

• Large droplets moving through cloud collide and coalesce with smaller slower droplets

Rain and Snow

• Rain- drops of water fall from a cloud• Low temperature six sided ice crystals form

which makes snow• At -5 degrees Celsius ice crystals join together

as clumps

Sleet, Glaze, and Hail

• Sleet- fall of small particles of clear ice• Glaze-known as freezing rain, occurs when

raindrops get super cooled• Hail-begin as small ice pellets, growing by

collective super cooled water droplets.